WO2020145343A1 - Plate-shaped spinel particles and method for producing same - Google Patents

Plate-shaped spinel particles and method for producing same Download PDF

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Publication number
WO2020145343A1
WO2020145343A1 PCT/JP2020/000442 JP2020000442W WO2020145343A1 WO 2020145343 A1 WO2020145343 A1 WO 2020145343A1 JP 2020000442 W JP2020000442 W JP 2020000442W WO 2020145343 A1 WO2020145343 A1 WO 2020145343A1
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molybdenum
plate
less
particles
compound
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PCT/JP2020/000442
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French (fr)
Japanese (ja)
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新吾 高田
建軍 袁
一男 糸谷
義之 佐野
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Dic株式会社
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Priority to JP2020565200A priority Critical patent/JPWO2020145343A1/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G39/00—Compounds of molybdenum
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/44—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminates
    • C04B35/443—Magnesium aluminate spinel

Definitions

  • the present invention relates to a plate-like spinel particle and a method for producing the same.
  • the inorganic particles having a plate-like shape with a high aspect ratio are particularly excellent in thermal characteristics and optical characteristics due to their unique shape.
  • inorganic fillers having excellent properties such as low dielectric constant (relative permittivity), Q value or dielectric loss tangent, mechanical strength, thermal conductivity, and thermal expansion coefficient are required.
  • Inorganic particles having such a high aspect ratio are drawing attention.
  • tabular alumina can be cited, and various studies have been made on the improvement of thermal conductivity and mechanical strength.
  • the dielectric loss tangent peculiar to alumina is as high as 10 ⁇ 3 , it is impossible to achieve a material having a low dielectric loss tangent in addition to thermal conductivity and mechanical strength.
  • examples of the inorganic particles having a low dielectric constant include double oxide spinel particles of a metal element represented by MgAl 2 O 4 and having the general formula AB 2 X 4 .
  • Patent Documents 1 and 2 disclose spinel particles having excellent thermal conductivity.
  • Patent Documents 1 and 2 have a large crystallite size, excellent thermal conductivity of the particles themselves, and low dielectric loss tangent or chemical resistance. Although the obtained cases can be seen, none of them having a low dielectric loss tangent and a high aspect ratio and excellent mechanical strength has been found yet.
  • the present invention has been made in view of the above circumstances, and provides plate-like spinel particles having excellent mechanical strength while maintaining a low dielectric loss tangent, and a method for producing the same.
  • the present inventors have found that plate-shaped ⁇ -alumina particles containing molybdenum and spinel particles obtained by firing a magnesium compound have a high aspect ratio and high mechanical strength.
  • the inventors have found that not only they are excellent, but also have a large crystallite size, excellent thermal conductivity, and a plate-like shape with a very small dielectric loss tangent, and have completed the present invention.
  • the present invention includes the following aspects.
  • the thickness T is 0.01 ⁇ m or more and 5 ⁇ m or less
  • the average particle diameter L is 0.1 ⁇ m or more and 500 ⁇ m or less
  • the aspect ratio L/T is 3 or more and 500 or less
  • molybdenum is included in the particles.
  • Plate-shaped spinel particles (2) The plate-shaped spinel particles according to (1), wherein the content of the molybdenum is 0.01% by mass or more and 1% by mass or less in terms of molybdenum trioxide with respect to 100% by mass of the plate-shaped spinel particles.
  • the plate-like shape according to (1) or (2) which has a crystallite diameter of 60 nm or more calculated from the half-value width of the peak corresponding to the (311) plane of the diffraction peak obtained by the X-ray diffraction method.
  • the method for producing plate-like spinel particles is the method for producing plate-like spinel particles according to any one of (1) to (3), wherein the magnesium compound and the aluminum compound are added in the presence of molybdenum. It is a manufacturing method of firing.
  • plate-like spinel particles and the method for producing the same in the above aspect it is possible to provide plate-like spinel particles having excellent mechanical strength while maintaining a low dielectric loss tangent.
  • FIG. 3 is an SEM image of spinel particles obtained in Examples and Comparative Examples.
  • the scale bar (solid line) in (A) to (E) is 10.0 ⁇ m.
  • the scale bar (dotted line) in (F) is 50.0 ⁇ m.
  • spinel particles contain a magnesium atom, an aluminum atom, and an oxygen atom, and thus are usually represented by a chemical composition of MgAl 2 O 4 .
  • the plate-like spinel particles according to the embodiment include molybdenum in the particles, the molybdenum containing form is not particularly limited, but molybdenum adheres to the surface of the spinel particles, coats, bonds, and forms similar to these, molybdenum. And a combination thereof.
  • the "form in which molybdenum is incorporated into the spinel" a form in which at least a part of atoms constituting the spinel particle is replaced with molybdenum, a space that may exist inside the crystal of the spinel particle (a space generated by a defect in the crystal structure And the like), and the like in which molybdenum is arranged.
  • the atom constituting the spinel particle to be substituted is not particularly limited and may be a magnesium atom, an aluminum atom, an oxygen atom, or any other atom.
  • molybdenum is preferably contained at least in a form incorporated in spinel. When molybdenum is incorporated in the spinel, it tends to be difficult to be removed by cleaning, for example.
  • the plate-like spinel particles according to the embodiment can have excellent mechanical strength while maintaining a low dielectric loss tangent because of the above-mentioned shape.
  • the conventional spinel particles did not satisfy at least one of the requirements of the thickness, average particle diameter and aspect ratio, as will be shown in Examples described later. Therefore, the conventional spinel particles have a low dielectric loss tangent but a poor mechanical strength, probably because they are not plate-like or have a small particle size. Since the plate-like spinel particles according to the embodiment have a high aspect ratio, it is considered that they can exhibit excellent mechanical strength.
  • the “aspect ratio” is the ratio of the average particle diameter of spinel particles divided by the thickness.
  • plate-like as used herein means that the aspect ratio is 2 or more.
  • the “thickness of spinel particles” is the arithmetic mean value of the thickness measured for at least 50 spinel particles randomly selected from an image obtained by a scanning electron microscope (SEM).
  • the “particle diameter” is the maximum length of the distance between two points on the contour line of the spinel particle.
  • the “average particle size of spinel particles” is the arithmetic mean value of the particle sizes measured for at least 50 plate-like spinel particles randomly selected from the images obtained by a scanning electron microscope (SEM).
  • the plate-like spinel particles according to the embodiment have a thickness of 0.01 ⁇ m or more and 5 ⁇ m or less, preferably 0.05 ⁇ m or more and 3 ⁇ m or less, more preferably 0.1 ⁇ m or more and 1 ⁇ m or less, and further preferably 0.15 ⁇ m or more and 0.75 ⁇ m or less. It is particularly preferably 0.2 ⁇ m or more and 0.5 ⁇ m or less, and most preferably 0.2 ⁇ m or more and 0.47 ⁇ m or less. When the thickness of the plate-like spinel particles is within the above range, the mechanical strength can be made more excellent.
  • the plate-like spinel particles according to the embodiment have an average particle size of 0.1 ⁇ m or more and 500 ⁇ m or less, preferably 0.3 ⁇ m or more and 100 ⁇ m or less, more preferably 0.5 ⁇ m or more and 50 ⁇ m or less, and further preferably 1 ⁇ m or more and 30 ⁇ m or less, It is more preferably 1 ⁇ m or more and 20 ⁇ m or less, particularly preferably 1 ⁇ m or more and 10 ⁇ m or less, and most preferably 4 ⁇ m or more and 9 ⁇ m or less.
  • the average particle diameter of the plate-like spinel particles is equal to or more than the lower limit value, it is possible to more effectively suppress an increase in viscosity when mixed with a resin or the like, while being equal to or less than the upper limit value.
  • the surface of the molded product containing the plate-like spinel particles can be made smoother.
  • the plate-like spinel particles according to the embodiment have an aspect ratio of 3 or more and 500 or less, preferably 5 or more and 100 or less, more preferably 7 or more and 50 or less, still more preferably 9 or more and 30 or less, still more preferably 10 or more and 25 or less. It is preferably 12 or more and 23 or less, particularly preferably 14.5 or more and 20 or less.
  • the aspect ratio is equal to or more than the above lower limit, the mechanical strength tends to be more excellent, while when the aspect ratio is less than or equal to the above upper limit, the surface of the molded article containing the plate-like spinel particles becomes smoother. It can be anything.
  • the conditions of thickness, average particle diameter, and aspect ratio can be combined in any manner as long as it is in a plate shape.
  • the plate-shaped spinel particles according to the embodiment may have a circular plate shape or an elliptical plate shape, but the particle shape is, for example, a polygonal plate shape such as hexagonal to octagonal, which has characteristics such as dielectric loss tangent and It is preferable from the viewpoints of handleability and ease of production.
  • the crystallite diameter of the (311) plane of the plate-like spinel particles according to the embodiment is preferably 60 nm or more, more preferably 65 nm or more, even more preferably 66 nm or more, even more preferably 70 nm or more.
  • the upper limit of the crystallite diameter of the (311) plane is not particularly limited and can be, for example, 200 nm or less, 150 nm or less, 100 nm or less, and 90 nm or less. And can be 82 nm or less.
  • the (311) plane is one of the main crystal domains of the spinel particle, and the size of the crystal domain of the (311) plane corresponds to the crystallite diameter of the (311) plane.
  • the crystallite size of the (311) plane of the spinel particles can be controlled by appropriately setting the conditions of the manufacturing method described later.
  • XRD X-ray diffraction
  • the spinel particles contain magnesium atoms, aluminum atoms, and oxygen atoms, and are generally represented by the composition of MgAl 2 O 4 .
  • the plate-like spinel particles according to the embodiment contain molybdenum.
  • the plate-like spinel particles according to the embodiment may contain other unavoidable impurities, other atoms, etc. as long as the effects of the present invention are not impaired.
  • the content of magnesium atoms in the spinel particles is not particularly limited, but for example, when the molar amount of aluminum atoms is 2 mol, it is preferably 0.8 mol or more and 1.2 mol or less, and 0.9 mol or less. More preferably, it is 1.1 mol or less.
  • the content of aluminum atoms in the spinel particles is not particularly limited, but for example, when the molar amount of magnesium atoms is 1 mol, it is preferably 1.8 mol or more and 2.2 mol or less, and 1.9 mol. More preferably, it is 2.1 mol or less.
  • the content of magnesium atoms and aluminum atoms in the spinel particles can be measured by inductively coupled plasma optical emission spectroscopy (ICP-AES).
  • the content of oxygen atoms in the spinel particles is not particularly limited, but depends on the molar amount of magnesium atoms and aluminum atoms.
  • the content of oxygen atoms in the spinel particles is preferably 3.8 mol or more and 4.2 mol or less, and preferably 3.9 mol or more. It is more preferably 4.1 mol or less.
  • Molybdenum may be contained due to the manufacturing method described below.
  • the molybdenum is not particularly limited, but includes molybdenum metal, molybdenum oxide, a partially reduced molybdenum compound, and the like. Molybdenum is considered to be included in the plate-shaped spinel particles as MoO 3, it may be included in the plate-shaped spinel particles as MoO 2 and MoO like in addition to MoO 3.
  • the contained form of molybdenum is not particularly limited, and may be contained in the form of being adhered, coated, bonded, or the like on the surface of the plate-like spinel particles, or in a form in which molybdenum is incorporated into the spinel. It may be contained or a combination thereof.
  • the content of molybdenum is not particularly limited, but from the viewpoint of high thermal conductivity of the plate-shaped spinel particles according to the embodiment, it should be 1% by mass or less in terms of molybdenum trioxide with respect to 100% by mass of the plate-shaped spinel particles. Is more preferable, 0.8% by mass or less is more preferable, from the viewpoint that the plate-shaped spinel particles exhibit higher density, 0.7% by mass or less is more preferable, and 0.65% by mass or less is It is even more preferable, and 0.61% by mass or less is particularly preferable.
  • the lower limit of the content of molybdenum is not particularly limited, but can be, for example, 0.01 mass% or more, 0.05 mass% or more, and 0.1 mass% or more.
  • the content of molybdenum in the plate-like spinel particles can be obtained by XRF analysis.
  • the XRF analysis is performed under the same measurement conditions as those described in Examples described later or under compatible conditions that the same measurement results are obtained.
  • the unavoidable impurities are present in the raw materials or are inevitably mixed in the plate-shaped spinel particles in the manufacturing process, and are essentially unnecessary, but they are in small amounts and affect the properties of the plate-shaped spinel particles. Means impurities that do not extend.
  • the unavoidable impurities include, but are not limited to, silicon, iron, potassium, sodium, calcium and the like. These unavoidable impurities may be contained alone or in combination of two or more.
  • the content of unavoidable impurities in the plate-like spinel particles is preferably 10000 ppm or less, more preferably 1000 ppm or less, and further preferably 10 ppm or more and 500 ppm or less, based on the mass of the plate-like spinel particles. ..
  • the other atom means one that is intentionally added to the spinel particles for the purpose of coloring, emitting light, controlling the formation of spinel particles, etc. within a range that does not impair the effects of the present invention.
  • atoms include, but are not limited to, zinc, cobalt, nickel, iron, manganese, titanium, zirconium, calcium, strontium, yttrium, and the like. These other atoms may be used alone or in combination of two or more.
  • the content of other atoms in the plate-shaped spinel particles is preferably 10% by mass or less, more preferably 5% by mass or less, and 2% by mass or less, relative to 100% by mass of the plate-shaped spinel particles. Is more preferable.
  • the method for producing the plate-like spinel particles according to the embodiment is not particularly limited, and known techniques may be appropriately applied, but the method includes a step of firing a magnesium compound and an aluminum compound in the presence of molybdenum (firing step).
  • the method is preferred.
  • the firing step may be a step of firing the mixture obtained in the step of obtaining the mixture to be fired (mixing step).
  • the mixing step is a step of mixing raw materials such as a magnesium compound, an aluminum compound and molybdenum to obtain a mixture.
  • the mixed state of the magnesium compound and the aluminum compound is not particularly limited. When both are mixed, simple mixing for mixing powders, mechanical mixing using a crusher or mixer, mixing using a mortar or the like is performed. At this time, the obtained mixture may be in a dry state or a wet state, but is preferably in a dry state from the viewpoint of cost.
  • the mixing ratio of the magnesium compound and the aluminum compound is not particularly limited, but the molar ratio of the aluminum element of the aluminum compound to the magnesium element of the magnesium compound (aluminum element/magnesium element) is 1.8 or more.2. It is preferable to mix so as to be 2 or less, and it is more preferable to mix so as to be 1.9 or more and 2.1 or less. The contents of the mixture will be described below.
  • the magnesium compound is not particularly limited, but examples thereof include metallic magnesium, magnesium derivatives, magnesium oxo acid salts, magnesium organic salts, and hydrates thereof.
  • the magnesium derivative include magnesium oxide, magnesium hydroxide, magnesium peroxide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, magnesium hydride, magnesium diboride, magnesium nitride and magnesium sulfide.
  • the magnesium oxo acid salt include magnesium carbonate, calcium magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium sulfite, magnesium perchlorate, trimagnesium phosphate, magnesium permanganate, magnesium phosphate and the like.
  • magnesium organic salt for example, magnesium acetate, magnesium citrate, magnesium malate, magnesium glutamate, magnesium benzoate, magnesium stearate, magnesium acrylate, magnesium methacrylate, magnesium gluconate, magnesium naphthenate, magnesium salicylate, lactic acid.
  • magnesium and magnesium monoperoxyphthalate examples thereof include magnesium and magnesium monoperoxyphthalate.
  • These magnesium compounds may be used alone or in combination of two or more. Among them, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium acetate, magnesium nitrate or magnesium sulfate is preferable, and magnesium oxide, magnesium hydroxide, magnesium nitrate or magnesium acetate is more preferable.
  • the average particle diameter of the magnesium compound is not particularly limited, but is preferably 1 ⁇ m or more and 10 ⁇ m or less, more preferably 1.5 ⁇ m or more and 5 ⁇ m or less, further preferably 2 ⁇ m or more and 4 ⁇ m or less, and particularly preferably 2.5 ⁇ m or more and 3.5 ⁇ m or more.
  • the average particle diameter of the magnesium compound is not less than the above lower limit, particle aggregation can be more effectively prevented in spinel crystallization.
  • the average particle diameter of the magnesium compound is not more than the above upper limit value, spinel crystallization can proceed to the central portion of the particles more efficiently.
  • the magnesium compound may be a commercially available product or may be prepared by itself.
  • the reactivity can be adjusted.
  • magnesium hydroxide having a small particle size can be obtained by neutralizing an acidic aqueous solution of magnesium ions with a base. Since the obtained magnesium hydroxide having a small particle size has high reactivity, the crystallite size of the spinel obtained using this tends to be large.
  • the aluminum compound is not particularly limited, but examples thereof include aluminum metal, aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, and aluminum oxide.
  • aluminum oxide include hydrated aluminum oxide, ⁇ -aluminum oxide, ⁇ -aluminum oxide, ⁇ -aluminum oxide, ⁇ -aluminum oxide, ⁇ -aluminum oxide, and mixed aluminum oxide having two or more crystal phases. Are listed.
  • the above-mentioned aluminum compound is preferably aluminum oxide, preferably aluminum oxide having at least one crystal form selected from the group consisting of ⁇ crystal, ⁇ crystal, ⁇ crystal, ⁇ crystal and ⁇ crystal, Aluminum oxide having ⁇ crystals is more preferable.
  • the above-mentioned aluminum compound preferably contains molybdenum.
  • the molybdenum-containing form of the aluminum compound containing molybdenum is not particularly limited, but like the spinel particles, molybdenum is attached to the surface of the aluminum compound, coated, bonded, or arranged in a form similar thereto, molybdenum. And a combination thereof.
  • the “form in which molybdenum is incorporated into the aluminum compound” a form in which at least a part of atoms constituting the aluminum compound is substituted with molybdenum, a space that may exist inside the crystal of the aluminum compound (occurs due to a defect in the crystal structure)
  • a form in which molybdenum is arranged in (including a space) is included.
  • the atoms constituting the aluminum compound to be substituted are not particularly limited and may be any of aluminum atoms, oxygen atoms and other atoms.
  • aluminum compounds it is preferable to use an aluminum compound containing molybdenum, and it is more preferable to use an aluminum compound containing molybdenum.
  • an aluminum compound containing molybdenum is preferable because it is due to the following mechanism. That is, molybdenum contained in the aluminum compound plays a role of promoting nucleation at the solid phase interface, promoting solid phase diffusion of aluminum atoms and magnesium atoms, etc., so that the solid phase reaction between the aluminum compound and magnesium compound proceeds more favorably. It is supposed to do. That is, as described later, the aluminum compound containing molybdenum can have a function as an aluminum compound and molybdenum. In particular, in an aluminum compound incorporating molybdenum, molybdenum is arranged directly or in the vicinity of the reaction point, and the effect of molybdenum can be more effectively exhibited. It should be noted that the above mechanism is only an estimation, and even if a desired effect can be obtained by a mechanism different from the above mechanism, it is included in the technical scope.
  • the shape of the aluminum compound is not particularly limited, and examples thereof include polyhedron, sphere, ellipse, column, polygonal column, needle, rod, plate, disc, flakes, and scales. Among them, as described below, the manufacturing method according to the embodiment tends to obtain spinel particles that reflect the shape of the aluminum compound, and thus the plate shape is preferable.
  • the average particle size of the aluminum compound is not particularly limited, but it is appropriately adjusted according to the particle size of the plate-like spinel to be obtained.
  • the average particle size of the aluminum compound is 0.1 ⁇ m or more and 500 ⁇ m or less, preferably 0.3 ⁇ m or more and 100 ⁇ m or less, more preferably 0.5 ⁇ m or more and 50 ⁇ m or less, further preferably 1 ⁇ m or more and 30 ⁇ m or less, and more preferably 1 ⁇ m or more and 20 ⁇ m or less. More preferably, it is particularly preferably 1 ⁇ m or more and 10 ⁇ m or less, most preferably 3.8 ⁇ m or more and 7.0 ⁇ m or less.
  • the average particle diameter of the aluminum compound is at least the above lower limit value, particle aggregation can be more effectively prevented in spinel crystallization.
  • the average particle diameter of the aluminum compound is not more than the above upper limit value, spinel crystallization can proceed more efficiently to the central portion of the particles.
  • the thickness of the aluminum compound is 0.01 ⁇ m or more and 5 ⁇ m or less, preferably 0.05 ⁇ m or more and 3 ⁇ m or less, more preferably 0.1 ⁇ m or more and 1 ⁇ m or less, still more preferably 0.15 ⁇ m or more and 0.75 ⁇ m or less, and 0.2 ⁇ m. Above 0.5 ⁇ m is particularly preferable. When the thickness of the aluminum compound is within the above range, plate-like spinel particles having a larger aspect ratio can be obtained.
  • the aspect ratio of the aluminum compound is 3 or more and 500 or less, preferably 5 or more and 100 or less, more preferably 7 or more and 50 or less, further preferably 9 or more and 30 or less, and particularly preferably 10 or more and 25 or less.
  • the aspect ratio is the above lower limit or more, plate-like spinel particles having more excellent mechanical strength can be obtained, while when the aspect ratio is not more than the above upper limit, a molded article or coating film having a smoother surface can be obtained. It becomes plate-like spinel particles that can be used.
  • the aluminum compound a commercially available product may be used, or an aluminum compound prepared by itself may be used.
  • the aluminum compound containing molybdenum can be prepared by the flux method described in detail below. That is, in a preferred embodiment, the method for producing spinel particles further includes the step of preparing an aluminum compound by the flux method.
  • the flux method is classified into the liquid-phase method, especially the solution method. More specifically, the flux method is a crystal growth method that utilizes the fact that the crystal-flux binary system phase diagram shows a eutectic type.
  • the mechanism of the flux method is presumed to be as follows. That is, as the mixture of solute and flux is heated, the solute and flux become a liquid phase. At this time, since the flux is a flux, in other words, since the solute-flux binary system phase diagram shows a eutectic type, the solute should be melted at a temperature lower than its melting point to form a liquid phase.
  • the concentration of the flux is lowered, in other words, the melting point lowering effect of the solute by the flux is reduced, and the flux evaporation serves as a driving force to cause solute crystal growth (flux). Evaporation method).
  • the solute and the flux can also cause solute crystal growth by cooling the liquid phase (slow cooling method).
  • the flux method has the advantages that crystals can be grown at a temperature much lower than the melting point, the crystal structure can be precisely controlled, and polyhedral crystals having an automorphism can be formed.
  • molybdenum compound When a molybdenum compound is used as the fluxing agent when preparing an aluminum compound by the flux method, an aluminum compound containing molybdenum can be obtained via the intermediate compound aluminum molybdate. At this time, molybdenum contained in the aluminum compound may correspond to a flux impurity which is said to be a disadvantage of the flux method. However, as described above, in one embodiment of the present invention, the molybdenum contained in the aluminum compound is plate-shaped. A suitable effect can be exhibited when producing spinel particles.
  • the flux method includes a flux evaporation step of firing a mixture containing an aluminum source and a molybdenum compound, and a cooling step of cooling the aluminum compound crystal-grown in the firing step.
  • the aluminum source is not particularly limited, but aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, transition alumina, alumina hydrate, ⁇ -alumina, and two or more crystals. Examples include mixed alumina having a phase. Examples of the transition alumina include ⁇ -alumina, ⁇ -alumina, ⁇ -alumina and the like.
  • the above aluminum sources may be used alone or in combination of two or more. Among them, aluminum hydroxide, transition alumina, boehmite, pseudo-boehmite or alumina hydrate is preferable, and aluminum hydroxide, transition alumina or boehmite is more preferable.
  • the aluminum source may be a commercially available product or may be prepared by itself.
  • alumina hydrate or transition alumina having high structural stability at high temperature can be prepared by neutralizing an aqueous solution of aluminum. More specifically, the alumina hydrate can be prepared by neutralizing an acidic aqueous solution of aluminum with a base, and the transition alumina is prepared by heat-treating the alumina hydrate obtained above. be able to.
  • the alumina hydrate or transition alumina thus obtained has high structural stability at high temperatures, and therefore, when calcined in the presence of molybdenum, an aluminum compound containing molybdenum having a large average particle diameter tends to be obtained.
  • the shape of the aluminum source is not particularly limited, and any shape such as spherical, amorphous, structural body with aspect, sheet, etc. can be preferably used.
  • a structure having an aspect for example, a wire, a fiber, a ribbon, a tube, or the like can be preferably used.
  • the particle size of the aluminum source is not particularly limited, and a solid aluminum compound of several nm to several hundreds of ⁇ m can be preferably used.
  • the aluminum source may form a complex with an organic compound.
  • the composite include an organic-inorganic composite obtained by modifying an aluminum compound with an organic silane, an aluminum compound composite adsorbing a polymer, a composite coated with an organic compound, and the like.
  • the content of the organic compound is not particularly limited, but is preferably 60% by mass or less, and more preferably 30% by mass or less.
  • the specific surface area of the aluminum source is also not particularly limited. Since the molybdenum compound acts effectively, it is preferable that the specific surface area is large, but by adjusting the firing conditions and the amount of the molybdenum compound used, any specific surface area can be used as a raw material.
  • a shape control agent can be used to form an aluminum compound.
  • the shape control agent plays an important role in the plate crystal growth of alumina by firing an aluminum source in the presence of a molybdenum compound.
  • the state of existence of the shape control agent is not particularly limited, and for example, a shape control agent, an aluminum compound and a physical mixture, a complex in which the shape control agent is present uniformly or locally on the surface or inside of the aluminum source, and the like are preferable. Can be used.
  • the shape control agent may be added to the aluminum compound, but may be included as an impurity in the aluminum compound.
  • Shape control agent plays an important role in plate crystal growth.
  • molybdenum oxide flux method that is generally performed, molybdenum oxide is selectively adsorbed on the (113) plane of ⁇ crystals of alumina, and the crystal component is less likely to be supplied to the (113) plane, and the (001) plane or ( Since the appearance of the (006) plane can be completely suppressed, polyhedral particles based on a hexagonal bipyramid are formed.
  • molybdenum oxide which is a flux agent, suppresses the selective adsorption of crystalline components on the (113) plane, so that the (001) plane is thermodynamically developed.
  • silicon or a silicon compound containing a silicon element, germanium or a germanium compound containing a germanium element can be used. It is preferable to use silicon or a silicon compound containing a silicon element from the viewpoint that it is possible to produce plate-like alumina particles that are less expensive and have excellent productivity.
  • An aluminum compound having a high aspect ratio can be easily produced by the flux method using silicon or a silicon compound as the shape control agent.
  • the silicon compound containing silicon or silicon element is not particularly limited, and known compounds can be used.
  • the silicon compound containing silicon or a silicon element may be an artificial synthetic silicon compound or a natural silicon compound.
  • Examples of the artificially synthesized silicon compound include metal silicon, organic silane, silicon resin, silica fine particles, silica gel, mesoporous silica, SiC, and mullite.
  • Examples of natural silicon compounds include biosilica and the like. Above all, it is preferable to use organic silane, silicon resin, or silica fine particles from the viewpoint that the compounding and mixing with the aluminum compound can be formed more uniformly.
  • the silicon compounds containing silicon or silicon element may be used alone or in combination of two or more kinds.
  • the shape of silicon or a silicon compound containing a silicon element is not particularly limited, and for example, a spherical shape, an amorphous shape, a structure having an aspect, a sheet, or the like can be preferably used.
  • a structure having an aspect for example, a wire, a fiber, a ribbon, a tube, or the like can be preferably used.
  • the content of silicon with respect to 100 mass% of the aluminum compound is preferably 10 mass% or less, more preferably 0.001 mass% or more and 5 mass% or less, further 0.01 mass% or more and 4 mass% or less in terms of silicon dioxide. It is preferably 0.6% by mass or more and 2.5% by mass or less.
  • the silicon content can be determined by XRF analysis.
  • the molybdenum compound molybdenum compound is not particularly limited, metallic molybdenum, molybdenum oxide, molybdenum sulfide, sodium molybdate, potassium molybdate, calcium molybdate, ammonium molybdate, H 3 PMo 12 O 40, H 3 SiMo 12 O 40 etc. are mentioned.
  • the molybdenum compound includes isomers.
  • molybdenum oxide may be molybdenum (IV) dioxide (MoO 2 ) or molybdenum trioxide (VI) (MoO 3 ).
  • the above molybdenum compounds may be used alone or in combination of two or more. Of these, molybdenum trioxide, molybdenum dioxide or ammonium molybdate is preferable, and molybdenum trioxide is more preferable.
  • the molar ratio of the molybdenum element of the molybdenum compound to the aluminum element of the aluminum compound is preferably 0.01 or more and 3.0 or less, and more preferably 0.03 or more and 1.0 or less. preferable.
  • the molar ratio is at least the above lower limit, crystal growth of the aluminum compound containing molybdenum can proceed more favorably.
  • the aluminum compound containing molybdenum can be prepared industrially more efficiently.
  • the firing temperature is not particularly limited, but is preferably 700° C. or higher and 2000° C. or lower, more preferably 900° C. or higher and 1600° C. or lower, further preferably 950° C. or higher and 1500° C. or lower, and 1000° C. or higher 1400 or higher. It is particularly preferable that the temperature is not higher than °C. If the firing temperature is at least the above lower limit, the flux reaction will proceed more suitably. On the other hand, when the firing temperature is at most the above upper limit, the burden on the firing furnace and the fuel cost can be further reduced.
  • the state of the aluminum source and the molybdenum compound during firing is not particularly limited as long as the molybdenum compound and the aluminum source exist in the same space.
  • the flux reaction can proceed even when the two are not mixed.
  • simple mixing of powders, mechanical mixing using a crusher, mixing using a mortar, etc. can be performed, and the resulting mixture is in a dry state. It may be in a wet state.
  • the firing time is also not particularly limited, but is preferably 5 minutes or more and 30 hours or less, and more preferably 10 minutes or more and 15 hours or less from the viewpoint of efficiently forming an aluminum compound containing molybdenum.
  • the firing atmosphere is also not particularly limited, but for example, an oxygen-containing atmosphere such as air or oxygen, or an inert atmosphere such as nitrogen or argon is preferable, and corrosion is performed from the viewpoint of the safety of the practitioner and the durability of the furnace. It is more preferable to use an oxygen-containing atmosphere having no property and a nitrogen atmosphere, and it is more preferable to use an air atmosphere from the viewpoint of cost.
  • the firing device is not particularly limited, and a so-called firing furnace is usually used.
  • the firing furnace is preferably made of a material that does not react with the sublimated molybdenum compound, and more preferably a highly tight firing furnace that can efficiently use the molybdenum compound.
  • the cooling step is a step of cooling the aluminum compound crystal-grown in the firing step.
  • the cooling rate is not particularly limited, but is preferably 1° C./hour or more and 1000° C./hour or less, more preferably 5° C./hour or more and 500° C./hour or less, and 50° C./hour or more 100° C./hour. More preferably, it is less than or equal to time. When the cooling rate is equal to or higher than the above lower limit value, the manufacturing time can be further shortened. On the other hand, when the cooling rate is less than or equal to the above upper limit, the firing container is less likely to be cracked by heat shock and can be used for a longer time, which is preferable.
  • the cooling method is not particularly limited, and natural cooling or a cooling device may be used.
  • the aluminum compound obtained by the flux method contains molybdenum, it is usually colored. Although the colored color varies depending on the amount of molybdenum contained, it is usually a light blue to a dark blue color close to black, and the color tends to become dark in proportion to the molybdenum content.
  • the aluminum compound containing molybdenum may be colored in another color. For example, the compound containing molybdenum may be red when it contains chromium, and may be yellow when it contains nickel.
  • the content of molybdenum in the aluminum compound containing molybdenum is not particularly limited, but is preferably 0.1% by mass or more and 1% by mass or less and 0.2% by mass or more and 0.9% by mass in terms of molybdenum trioxide. It is more preferably at most 0.3% by mass and at most 0.9% by mass, even more preferably at least 0.5% by mass and at most 0.88% by mass, and at least 0.7% by mass. 0.87 mass% or less is particularly preferable, and 0.83 mass% or more and 0.86 mass% or less is most preferable. When the content of molybdenum is not less than the above lower limit, spinel crystal growth can proceed more efficiently.
  • the content of molybdenum is not more than the above upper limit value, the crystal quality of the aluminum compound can be improved, which is preferable.
  • the content of molybdenum in the aluminum compound can be measured by the same method as the method described in the content of molybdenum in the plate-like spinel particles.
  • the aluminum compound containing molybdenum preferably has a high ⁇ crystallization rate with molybdenum serving as a flux agent and having a crystal plane other than the (001) plane as a main crystal plane, and the ⁇ crystallization rate is 90% or more. Is more preferable.
  • the flux method includes a step of firing a mixture containing an aluminum source and a molybdenum compound, and a slow cooling step of cooling the obtained fired material to grow crystals.
  • Molybdenum has a function of promoting nucleation at the interface in the solid phase reaction, promoting solid phase diffusion of at least one atom of magnesium atom and aluminum atom, and the like.
  • molybdenum in a compound containing molybdenum metal and molybdenum may be used.
  • the compound containing molybdenum include the above-mentioned molybdenum compound and the aluminum compound containing molybdenum.
  • the aluminum compound containing molybdenum can be used as a compound containing molybdenum and an aluminum compound.
  • the above molybdenum may be used alone or in combination of two or more kinds.
  • the molar ratio of molybdenum element to aluminum element of the aluminum compound is preferably 0.00001 or more and 0.05 or less, and 0.0001 or more and 0.03 or less. Is more preferable. When the molar ratio is within the above range, solid solution of the magnesium compound and the aluminum compound and spinel crystallization can proceed more favorably.
  • a magnesium compound and an aluminum compound are added in the presence of molybdenum, It is a step of crystallizing the plate-like spinel particles by solid solution and crystallization.
  • the solid solution and crystallization are usually carried out by the so-called solid phase method.
  • the mechanism of solid solution and crystallization in the solid phase method is presumed to be as follows. That is, when heating is performed in an environment in which the magnesium compound and the aluminum compound are in contact with each other, the magnesium compound and the aluminum compound form nuclei at the interface (solid phase interface), so that the bond between the solid phases is strengthened. Then, the solid phase reaction can proceed using the formed nucleus as a carrier. At this time, the solid phase reaction is that the binary phase diagram of the magnesium compound and the aluminum compound has a eutectic type, whereby the temperature at which the magnesium compound and the aluminum compound can react at the interface is the magnesium compound or the aluminum compound alone. Lower than melting temperature can be utilized.
  • the magnesium compound and the aluminum compound react at the interface to form a nucleus, and at least one atom of the magnesium atom and the aluminum atom is solid-phase diffused through the nucleus, and the aluminum compound and the magnesium atom. Reacts with at least one of the atoms. Thereby, a dense crystal body, that is, spinel particles can be obtained.
  • the diffusion rate of magnesium atoms into the aluminum compound is relatively higher than the diffusion rate of aluminum atoms into the magnesium compound, so that spinel particles in which the shape of the aluminum compound is reflected are obtained. Tend. Therefore, it may be possible to control the shape and the average particle diameter of the spinel particles by appropriately changing the shape and the average particle diameter of the aluminum compound.
  • the plate-shaped spinel particles can be manufactured more easily by using the plate-shaped alumina particles containing molybdenum as the aluminum compound.
  • the above solid-phase reaction is performed in the presence of molybdenum.
  • molybdenum is not always clear, for example, solid-phase reaction proceeds more favorably by promoting nucleation at the interface, promoting solid-phase diffusion of at least one of magnesium and aluminum atoms, and the like. it is conceivable that.
  • flux method as a process of the reaction, first, molybdenum and an aluminum compound are reacted to form an aluminum intermediate molybdate, and then the aluminum molybdate and the magnesium compound are reacted. It is presumed to include things that do.
  • the crystallite size of the (311) plane of the spinel particles is controlled by changing the amount of molybdenum used, the type of magnesium compound, the firing temperature, the firing time, and the mixed state of the magnesium compound and the aluminum compound. be able to.
  • the reason is that the amount of molybdenum, the type of magnesium compound, the firing temperature, the firing time, and the mixed state of the magnesium compound and the aluminum compound depend on the rate of solid solution and crystallization in the magnesium compound and the aluminum compound in the solid phase reaction. It is considered to be related.
  • the use of a highly reactive magnesium compound increases the rate of solid solution and crystallization of the magnesium compound, and the increase in the amount of molybdenum used, high temperature calcination, and long time calcination solidify at least one of magnesium and aluminum atoms. And the rate of crystallization can be respectively increased, and for example, the crystallite diameter of the (311) plane can be increased.
  • the firing temperature is not particularly limited, but is preferably lower than 1300°C, more preferably 800°C or higher and lower than 1300°C, and further preferably 900°C or higher and 1200°C or lower.
  • the firing temperature is at most the above upper limit, the plate-like spinel particles can be produced more efficiently in a shorter time.
  • the firing temperature is not more than the above upper limit, the shape and dispersibility of spinel particles can be controlled more easily.
  • the firing time is not particularly limited, but is preferably 0.1 hour or more and 1000 hours or less, and more preferably 3 hours or more and 100 hours or less.
  • the firing time is at least the above lower limit, plate-like spinel particles having a larger crystallite size on the (311) plane can be obtained.
  • the firing time is not more than the above upper limit value, the manufacturing cost may be lower.
  • a shape control agent in order to promote the solid solution and crystallization of the magnesium compound and the aluminum compound and to control the shape.
  • the shape control agent include sodium compounds and potassium compounds.
  • the sodium compound is not particularly limited and includes sodium, sodium chloride, sodium chlorite, sodium chlorate, sodium sulfate, sodium hydrogen sulfate, sodium sulfite, sodium hydrogen sulfite, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, sodium acetate. , Sodium oxide, sodium bromide, sodium bromate, sodium hydroxide, sodium silicate, sodium phosphate, sodium hydrogen phosphate, sodium sulfide, sodium hydrogen sulfide, sodium molybdate, sodium tungstate and the like. At this time, the sodium compound includes isomers as in the case of the molybdenum compound.
  • sodium carbonate, sodium hydrogen carbonate, sodium oxide, sodium hydroxide, sodium chloride, sodium sulfate or sodium molybdate is preferably used, and sodium carbonate, sodium hydrogen carbonate, sodium chloride, sodium sulfate or sodium molybdate is used. Is more preferable.
  • the sodium compounds described above may be used alone or in combination of two or more. Further, since sodium molybdate contains molybdenum, it can also have a function as the above-mentioned molybdenum compound.
  • the potassium compound is not particularly limited, potassium, potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium acetate, Examples thereof include potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, potassium tungstate, and the like.
  • the potassium compound includes isomers, as in the case of the molybdenum compound.
  • potassium carbonate, potassium hydrogen carbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate or potassium molybdate is preferably used, and potassium carbonate, potassium hydrogen carbonate, potassium chloride, potassium sulfate or potassium molybdate is used. Is more preferable.
  • the above potassium compounds may be used alone or in combination of two or more. Further, since potassium molybdate contains molybdenum, it can also have a function as the above-mentioned molybdenum compound.
  • the amount of the shape control agent added is preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 80% by mass or less, in terms of oxide, based on 100% by mass of the raw material. , 40% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 68% by mass or less, particularly preferably 55% by mass or more and 67% by mass or less, and 61% by mass or more and 66% by mass or less. Most preferred.
  • the amount of the shape control agent added is within the above range, it is possible to obtain plate-like spinel particles having more excellent surface smoothness. Further, the aspect ratio can be increased, and the mechanical strength tends to be superior.
  • These additives are preferably mixed in the above mixing step before firing.
  • the firing atmosphere may be an air atmosphere, an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen atmosphere, an ammonia gas atmosphere, or a carbon dioxide atmosphere. It may be. At this time, an air atmosphere is preferable from the viewpoint of manufacturing cost.
  • the pressure during firing is also not particularly limited, and may be under normal pressure, may be under pressure, or may be under reduced pressure, but molybdenum oxide vapor generated during firing can be efficiently generated from the firing furnace. From the viewpoint of being able to discharge, it is preferable to carry out under reduced pressure.
  • the heating means is preferably a firing furnace, which is not particularly limited.
  • firing furnaces that can be used at this time include tunnel furnaces, roller hearth furnaces, rotary kilns, and muffle furnaces. It is preferable that the firing furnace is made of a material that does not react with molybdenum oxide vapor, and it is more preferable to use a firing furnace having high airtightness.
  • the manufacturing method of the present invention may include a cooling step.
  • the cooling step is a step of cooling the spinel particles having crystal grown in the firing step.
  • the cooling rate is not particularly limited, but is preferably 1° C./hour or more and 1000° C./hour or less, more preferably 5° C./hour or more and 500° C./hour or less, and 50° C./hour or more 100° C./hour. More preferably, it is less than or equal to time. When the cooling rate is equal to or higher than the above lower limit value, the manufacturing time can be further shortened. On the other hand, when the cooling rate is less than or equal to the above upper limit, the firing container is less likely to be cracked by heat shock and can be used for a longer time.
  • the cooling method is not particularly limited, and natural cooling may be used, or a cooling device may be used.
  • the manufacturing method of the present invention may include a post-treatment step.
  • the post-treatment step is a step of removing additives and the like.
  • the post-treatment step may be performed after the above-mentioned firing step, may be performed after the above-mentioned cooling step, or may be performed after the firing step and the cooling step. Moreover, you may repeat twice or more as needed.
  • Examples of the post-treatment method include washing and high temperature treatment. These can be performed in combination.
  • the washing method is not particularly limited, but it can be removed by washing with water, an aqueous ammonia solution, an aqueous sodium hydroxide solution, an acidic aqueous solution, or the like.
  • the molybdenum content can be controlled by appropriately changing the concentration, the amount of water used, the aqueous ammonia solution, the aqueous sodium hydroxide solution, the acidic aqueous solution, the washing site, the washing time, and the like.
  • a method of high temperature treatment a method of raising the temperature above the sublimation point or boiling point of the additive can be mentioned.
  • plate-like spinel particles may aggregate and may not satisfy the particle size range suitable for the present invention. Therefore, the plate-like spinel particles may be pulverized, if necessary, so as to satisfy the particle size range suitable for the present invention.
  • the method for pulverizing the fired product is not particularly limited, and conventionally known pulverizing methods such as a ball mill, a jaw crusher, a jet mill, a disc mill, a spectro mill, a grinder, and a mixer mill can be applied.
  • the plate-like spinel particles are preferably classified in order to adjust the average particle size and improve the fluidity of the powder, or to suppress an increase in viscosity when blended in a binder for forming a matrix. ..
  • the "classifying treatment” refers to an operation of grouping particles according to the size of the particles.
  • the classification may be either wet or dry, but from the viewpoint of productivity, dry classification is preferred.
  • Dry classification in addition to classification by a sieve, there is a wind classification that classifies by the difference in centrifugal force and fluid drag force, but from the viewpoint of classification accuracy, wind classification is preferable, and an air classifier that utilizes the Coanda effect, It can be performed using a classifier such as a swirling air flow classifier, a forced vortex centrifugal classifier, a semi-free vortex centrifugal classifier, or the like.
  • the crushing step and the classification step described above can be performed at necessary stages, including before and after the organic compound layer forming step described later.
  • the average particle size of the obtained plate-like spinel particles can be adjusted by the presence or absence of the pulverization or classification and the selection of the conditions.
  • the temperature was lowered to room temperature under the condition of 5° C./min, and the crucible was taken out to obtain 99 g of a light blue powder.
  • the obtained powder was crushed in a mortar until it passed through a 106 ⁇ m sieve.
  • 98 g of the obtained light blue powder was dispersed in 150 mL of 0.5% aqueous ammonia, the dispersion solution was stirred at room temperature (25 to 30° C.) for 0.5 hours, and then the aqueous ammonia was removed by filtration. Molybdenum remaining on the surface of the particles was removed by washing with water and drying to obtain 96 g of white powder.
  • the obtained powder had an average particle size of 7.0 ⁇ m as determined by a laser diffraction type particle size distribution analyzer, and had a polygonal plate shape by SEM observation, which had very few aggregates and had excellent handleability. It was confirmed that the particles were shaped like particles. Further, when XRD measurement was carried out, sharp peak scattering derived from ⁇ -alumina appeared, and no alumina crystal system peak other than ⁇ crystal structure was observed, which confirmed that the plate-like alumina had a dense crystal structure. .. Moreover, the alpha conversion rate was 90% or more. Furthermore, it was confirmed from the results of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.83 mass% of molybdenum in terms of molybdenum trioxide. Furthermore, the result of measuring the density was 3.95 g/cm 3 .
  • ⁇ Synthesis Example 2 Synthesis of ⁇ -alumina particles A-2 145.3 g of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., average particle diameter 2 ⁇ m), 2.85 g of silicon dioxide, and molybdenum trioxide (Taiyo Mining Co., Ltd.) The same operation as in Synthesis Example 1 was carried out except that 5 g of the product) was mixed in a mortar to obtain 98 g of a pale blue powder. The obtained powder had an average particle diameter of 3.8 ⁇ m as determined by a laser diffraction type particle size distribution analyzer, and had a polygonal plate shape by SEM observation, which had very few aggregates and had excellent handleability.
  • the particles were shaped like particles. Further, when XRD measurement was carried out, sharp peak scattering derived from ⁇ -alumina appeared, and no alumina crystal system peak other than ⁇ crystal structure was observed, which confirmed that the plate-like alumina had a dense crystal structure. .. Moreover, the alpha conversion rate was 90% or more. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained molybdenum in an amount of 0.86% by mass in terms of molybdenum trioxide. Furthermore, the result of measuring the density was 3.94 g/cm 3 .
  • the obtained powder was crushed in a mortar until it passed through a 150 ⁇ m sieve. Subsequently, 25 g of the obtained white powder and 100 mL of 2% nitric acid were blended, alumina beads having a diameter of 5 mm were added, and 20 pieces were crushed and crushed with a paint conditioner. Thereafter, the dispersion solution was filtered to remove 2% nitric acid, and washed with water and dried to remove the molybdenum remaining on the surface of the particles to obtain 24.5 g of white powder. It was confirmed by SEM observation (see FIG. 1A) that the obtained powder was plate-like, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed.
  • the crystallite size was determined from the peak of the (311) plane observed near 37 degrees using a CALSA detector, it was confirmed to be 72 nm. Furthermore, it was confirmed from the results of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.44% by mass of molybdenum in terms of molybdenum trioxide.
  • Example 2 Synthesis of spinel particles S-a2 The obtained mixture was put into a crucible, heated to 1150°C under a condition of 5°C/min in a ceramic electric furnace, and kept at 1150°C for 10 hours for firing. Except for the above, the same operation as in Example 1 was performed to obtain 24.5 g of white powder. It was confirmed by SEM observation (see FIG. 1B) that the obtained powder was plate-like, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Further, the crystallite size was found to be 82 nm from the peak of the (311) plane observed at around 37 degrees using a CALSA detector, and it was 82 nm.
  • Example 1 Compared with the 1050° C. firing of Example 1, the crystal was obtained by firing at a higher temperature. It was confirmed to be significant for growth. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.48% by mass of molybdenum in terms of molybdenum trioxide.
  • Example 3 Synthesis of Spinel Particles Sa3 20 g of ⁇ -alumina particles A-2 obtained in Synthesis Example 2 and 7.86 g of magnesium oxide (average particle diameter 3.5 ⁇ m, manufactured by Kamijima Chemical Co., Ltd.) were mixed in a mortar. The same operation as in Example 1 was carried out except that a mixture was obtained to obtain 24.6 g of white powder. The average particle size of the obtained powder was 4.0 ⁇ m, and the average particle size was 3.8 ⁇ m, which was smaller than the ⁇ -alumina particles A-1 obtained in Synthesis Example 1, and ⁇ -alumina particles obtained in Synthesis Example 2 were obtained. When A-2 was used, particles having an average particle size smaller than that of the plate-like spinel particles Sa1 obtained in Example 1 were obtained.
  • Example 4 Synthesis of Spinel Particles S-a4 20 g of ⁇ -alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (Kamishima Chemical Co., Ltd. average particle size 3.5 ⁇ m), and molybdenum trioxide 1 The same operation as in Example 1 was carried out except that 0.67 g was mixed in a mortar to obtain a mixture, to obtain 24.6 g of a white powder. It was confirmed by SEM observation (see FIG. 1D) that the obtained powder was plate-shaped, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed.
  • the crystallite size was determined from the peak of the (311) plane observed at around 37 degrees using a CALSA detector, and was found to be 88 nm.
  • the crystallite size was calcined in the composition of Example 2 without addition of molybdenum trioxide. It was confirmed that molybdenum trioxide contributed to the crystal growth because the crystallite size was large compared with. Furthermore, it was confirmed from the results of the fluorescent X-ray quantitative analysis that the obtained particles contained molybdenum in an amount of 0.61% by mass in terms of molybdenum trioxide.
  • Example 5 Synthesis of spinel particles S-a5 20 g of ⁇ -alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (manufactured by Kamijima Chemical Co., Ltd., average particle diameter 3.5 ⁇ m), and sodium chloride 83. The same operation as in Example 1 was carried out except that 57 g was mixed in a mortar to obtain a mixture, and 24.5 g of white powder was obtained. The average particle diameter of the obtained powder was 8.3 ⁇ m, and by adding sodium chloride, particles having an average particle diameter larger than that of the plate-like spinel particles Sa2 obtained in Example 2 were obtained. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed.
  • the crystallite size was found to be 66 nm by using a CALSA detector and determining the crystallite size from the peak of the (311) plane observed near 37 degrees. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.31 mass% of molybdenum in terms of molybdenum trioxide.
  • Example 6 Synthesis of spinel particles S-a6 20 g of ⁇ -alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (manufactured by Kamijima Chemical Co., Ltd., average particle diameter 3.5 ⁇ m), and sodium chloride 83. The same operation as in Example 1 was carried out except that 57 g was mixed in a mortar to obtain a mixture, and 24.5 g of white powder was obtained. The average particle diameter of the obtained powder was 8.0 ⁇ m, and by adding potassium chloride in the same manner as in Example 5, particles having an average particle diameter larger than that of the plate-like spinel particles S-a2 obtained in Example 2 were obtained. Was obtained.
  • the crystallite size was found to be 68 nm by using a CALSA detector and determining the crystallite size from the peak of the (311) plane observed at around 37 degrees. Furthermore, it was confirmed from the results of the fluorescent X-ray quantitative analysis that the obtained particles contained 0.33% by mass of molybdenum in terms of molybdenum trioxide.
  • the obtained powder was crushed in a mortar until it passed through a 150 ⁇ m sieve. Subsequently, 25 g of the obtained white powder and 100 mL of 2% nitric acid were blended, alumina beads having a diameter of 5 mm were added, and 20 pieces were crushed and crushed with a paint conditioner. Then, the dispersed solution was filtered to remove 2% nitric acid, washed with water and dried to obtain 24.6 g of white powder. When the obtained powder was observed by SEM (see FIG. 1(E)), it was plate-shaped, but the particle shape and particle diameter were uneven.
  • the average thickness of the plate was 1 ⁇ m
  • the average particle size determined by a laser diffraction type particle size distribution meter was 2.9 ⁇ m
  • the aspect ratio determined by the average particle size/thickness average was 2.9.
  • the value was extremely smaller than the aspect ratio of the plate-like spinel particles obtained in No. 6.
  • peak scattering derived from spinel was observed, but the peak was broader than that of the plate-like spinel particles obtained in Examples 1 to 6, and the peak was broadened.
  • the crystallite diameter was found to be 28 nm from the peak of the (311) plane observed at around 37 degrees, which was extremely smaller than the crystallite diameter of the plate-like spinel particles obtained in Examples 1 to 6. It became a value.
  • ⁇ Comparative Example 2 Synthesis of spinel particles S-b2 To 25 g of commercially available spinel particles (adjusted by sieving to an average particle diameter of 20 ⁇ m), 25 g of alumina beads having a diameter of 5 mm was added and crushed using a paint conditioner, 24.7 g of spinel particle powder was obtained. When the obtained powder was observed by SEM (see FIG. 1(F)), it was found to be angular particles having irregular particle shapes and particle sizes. Further, the average thickness of the plate was 5.3 ⁇ m, the average particle diameter obtained by a laser diffraction type particle size distribution meter was 5.5 ⁇ m, and the aspect ratio obtained by the average particle diameter/thickness average was 1.0.
  • the value was extremely smaller than the aspect ratio of the plate-like spinel particles obtained in 1 to 6. Further, when XRD measurement was performed, peak scattering derived from spinel was observed. Using a CALSA detector, the crystallite size was found to be 88 nm from the peak of the (311) plane observed at around 37 degrees.
  • the prepared sample is placed on a holder for a measurement sample having a depth of 0.5 mm and filled so as to be flat with a constant load, and the sample is set in a wide-angle X-ray diffractometer (Rint-Ultma manufactured by Rigaku Corporation), and Cu/ The measurement was performed under the conditions of K ⁇ ray, 40 kV/30 mA, scan speed 2°/min, and scanning range 10° or more and 70° or less. The ⁇ conversion rate was calculated from the ratio of the strongest peak heights of ⁇ -alumina and transition alumina.
  • the prepared sample is pretreated under the condition of 300° C. for 3 hours, and then measured using a dry automatic densimeter Acupic II 1330 manufactured by Micromeritics under the conditions of measuring temperature of 25° C. and using helium as a carrier gas. did.
  • Aspect ratio average particle diameter L of plate-like spinel particles/thickness T of plate-like spinel particles
  • the prepared sample is placed on a holder for a measurement sample having a depth of 0.5 mm and filled so as to be flat with a constant load, and the sample is set in a wide-angle X-ray diffraction (XRD) device (Rint-Ultma manufactured by Rigaku Corporation). , Cu/K ⁇ ray, 40 kV/30 mA, scan speed of 2°/min, and scanning range of 10° to 70°.
  • XRD wide-angle X-ray diffraction
  • the crystallite diameter (nm) of the (311) plane was determined from the peak observed at around 37 degrees under the following conditions using an X-ray diffractometer SmartLab manufactured by Rigaku Corporation and a detector CALSA.
  • the prepared sample is pretreated under the condition of 300° C. for 3 hours, and then measured using a dry automatic densimeter Acupic II 1330 manufactured by Micromeritics under the conditions of measuring temperature of 25° C. and using helium as a carrier gas. did.
  • Alumina beads having a diameter of 5 mm were added to 25 g of the prepared sample and treated with a paint conditioner for 4 hours to pulverize the spinel particles.
  • the relative permittivity and dielectric loss tangent were determined under the conditions of perturbation type resonator method, frequency 1 GHz, temperature 25° C. and humidity 50%.
  • the prepared sample was blended in an amount of 66 wt% and a polyphenylene sulfite resin (PPS resin DIC MA-500) 34 wt% to prepare a total of 20 g of a mixture.
  • 20 g of the mixture was melt-kneaded for 2 minutes under the conditions of an extruder temperature of 300° C. and a screw rotation speed of 150 rpm using a twin-screw kneader equipped with a full flight screw.
  • the obtained kneaded product was taken out from the die in a strand form, pelletized, and then, using a small injection molding machine, a dumbbell test piece having a width of 5 mm, a length of 75 mm and a thickness of 1 mm was obtained.
  • a dumbbell test piece having a width of 5 mm, a length of 75 mm and a thickness of 1 mm was obtained.
  • the crosshead is moved at a moving speed of 1 mm/min at an intermediate position between the two points on the side opposite to this.
  • the spinel particles S-b1 obtained in Comparative Example 1 and the spinel particles Sb-2 obtained in Comparative Example 2 had an aspect ratio higher than that of the spinel particles S-a1 to S-a6 obtained in Examples 1 to 6.
  • the spinel particles S-b1 obtained in Comparative Example 1 had a small crystallite size, resulting in a remarkably low bending stress.
  • the spinel particles of the present embodiment have a high aspect ratio and thus have excellent mechanical properties while maintaining peculiar properties such as dielectric constant and dielectric loss tangent.
  • the plate-like spinel particles and the manufacturing method thereof of the present embodiment it is possible to provide plate-like spinel particles having excellent mechanical strength while keeping the dielectric loss tangent low.

Abstract

The plate-shaped spinel particles have a thickness (T) of 0.01 to 5 μm (inclusive), an average particle diameter (L) of 0.1 to 500 μm (inclusive), and an aspect ratio (L/T) of 3 to 500 (inclusive), and contain molybdenum within the particles. The method for producing the plate-shaped spinel particles is a production method for firing a magnesium compound and an aluminum compound in the presence of molybdenum.

Description

板状スピネル粒子及びその製造方法Plate-shaped spinel particles and method for producing the same
　本発明は、板状スピネル粒子及びその製造方法に関する。 The present invention relates to a plate-like spinel particle and a method for producing the same.
　高アスペクト比の板状形状を持つ無機粒子は、その特異な形状による熱的特性及び光学特性等に特に優れている。現在、自動車や電子部品用途において、低誘電率（比誘電率）、Ｑ値又は誘電正接、機械強度、熱伝導率、熱膨張係数等の物性により優れた無機フィラーが求められており、上記のような高アスペクト比を持つ無機粒子が注目されている。アスペクト比を持つ無機粒子としては、板状アルミナが挙げられ、熱伝導率や機械強度向上等の様々な研究がなされている。しかし、アルミナ固有の誘電正接は１０－３と高いことにより、熱伝導率及び機械強度に加え低誘電正接を兼備したものは成し得ない。 The inorganic particles having a plate-like shape with a high aspect ratio are particularly excellent in thermal characteristics and optical characteristics due to their unique shape. At present, in automobiles and electronic parts, inorganic fillers having excellent properties such as low dielectric constant (relative permittivity), Q value or dielectric loss tangent, mechanical strength, thermal conductivity, and thermal expansion coefficient are required. Inorganic particles having such a high aspect ratio are drawing attention. As the inorganic particles having an aspect ratio, tabular alumina can be cited, and various studies have been made on the improvement of thermal conductivity and mechanical strength. However, since the dielectric loss tangent peculiar to alumina is as high as 10 −3 , it is impossible to achieve a material having a low dielectric loss tangent in addition to thermal conductivity and mechanical strength.
　一方、低誘電率の無機粒子としては、ＭｇＡｌ２Ｏ４で表わされる、一般式ＡＢ２Ｘ４となる金属元素の複酸化物スピネル粒子が挙げられる。特許文献１及び２には、熱伝導性に優れるスピネル粒子が開示されている。 On the other hand, examples of the inorganic particles having a low dielectric constant include double oxide spinel particles of a metal element represented by MgAl 2 O 4 and having the general formula AB 2 X 4 . Patent Documents 1 and 2 disclose spinel particles having excellent thermal conductivity.
　しかしながら、特許文献１、２等に開示された、従来のスピネル粒子においては、結晶子径が大きく、粒子自体の熱伝導率が優れ、かつ低誘電正接、あるいは耐薬品性に優れるであるものが得られる事例は見られるものの、低誘電正接及び高アスペクト比を有し、優れた機械強度を兼備するものは未だ見出されていない。 However, the conventional spinel particles disclosed in Patent Documents 1 and 2 have a large crystallite size, excellent thermal conductivity of the particles themselves, and low dielectric loss tangent or chemical resistance. Although the obtained cases can be seen, none of them having a low dielectric loss tangent and a high aspect ratio and excellent mechanical strength has been found yet.
日本国特開２０１６－１３５８４１号公報Japanese Unexamined Patent Publication No. 2016-135841 国際公開第２０１７／２２１３７２号International Publication No. 2017/221372
　本発明は、上記事情に鑑みてなされたものであって、誘電正接を低く保ちながら、優れた機械強度を有する板状スピネル粒子及びその製造方法を提供する。 The present invention has been made in view of the above circumstances, and provides plate-like spinel particles having excellent mechanical strength while maintaining a low dielectric loss tangent, and a method for producing the same.
　本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、モリブデンを含む板状α－アルミナ粒子及びマグネシウム化合物を焼成して得られたスピネル粒子は、アスペクト比が高く、機械強度に優れるのみならず、結晶子径も大きく熱伝導率に優れ、かつ誘電正接が極めて小さい板状の形状を有するものであることを見出し、本発明を完成するに至った。 As a result of intensive studies to achieve the above object, the present inventors have found that plate-shaped α-alumina particles containing molybdenum and spinel particles obtained by firing a magnesium compound have a high aspect ratio and high mechanical strength. The inventors have found that not only they are excellent, but also have a large crystallite size, excellent thermal conductivity, and a plate-like shape with a very small dielectric loss tangent, and have completed the present invention.
　すなわち、本発明は、以下の態様を含む。
（１）厚みＴが０．０１μｍ以上５μｍ以下であり、平均粒子径Ｌが０．１μｍ以上５００μｍ以下であり、アスペクト比Ｌ／Ｔが３以上５００以下であり、かつ粒子内にモリブデンを含む、板状スピネル粒子。
（２）前記モリブデンの含有量が、板状スピネル粒子１００質量％に対して三酸化モリブデン換算で０．０１質量％以上１質量％以下である、（１）に記載の板状スピネル粒子。
（３）Ｘ線回折法により得られる回折ピークの、（３１１）面に相当するピークの半値幅から算出される結晶子径が６０ｎｍ以上である、（１）又は（２）に記載の板状スピネル粒子。
（４）板状スピネル粒子の製造方法は、（１）～（３）のいずれか一つに記載の板状スピネル粒子の製造方法であって、マグネシウム化合物及びアルミニウム化合物を、モリブデン存在下で、焼成させる、製造方法である。
（５）前記アルミニウム化合物が板状アルミナ粒子である、（４）に記載の製造方法。
（６）前記アルミニウム化合物がモリブデンを三酸化モリブデン換算で０．１質量％以上１質量％以下含む、（４）又は（５）に記載の製造方法。
（７）焼成時に形状制御剤としてナトリウム化合物又はカリウム化合物を用いる、（４）～（６）のいずれか一つに記載の製造方法。
（８）１３００℃未満で焼成させる、（４）～（７）のいずれか一つに記載の製造方法。
（９）前記アルミニウム化合物及び前記マグネシウム化合物の平均粒子径が１μｍ以上１０μｍ以下である、（４）～（８）のいずれか一つに記載の製造方法。 That is, the present invention includes the following aspects.
(1) The thickness T is 0.01 μm or more and 5 μm or less, the average particle diameter L is 0.1 μm or more and 500 μm or less, the aspect ratio L/T is 3 or more and 500 or less, and molybdenum is included in the particles. Plate-shaped spinel particles.
(2) The plate-shaped spinel particles according to (1), wherein the content of the molybdenum is 0.01% by mass or more and 1% by mass or less in terms of molybdenum trioxide with respect to 100% by mass of the plate-shaped spinel particles.
(3) The plate-like shape according to (1) or (2), which has a crystallite diameter of 60 nm or more calculated from the half-value width of the peak corresponding to the (311) plane of the diffraction peak obtained by the X-ray diffraction method. Spinel particles.
(4) The method for producing plate-like spinel particles is the method for producing plate-like spinel particles according to any one of (1) to (3), wherein the magnesium compound and the aluminum compound are added in the presence of molybdenum. It is a manufacturing method of firing.
(5) The production method according to (4), wherein the aluminum compound is plate-like alumina particles.
(6) The production method according to (4) or (5), wherein the aluminum compound contains molybdenum in an amount of 0.1% by mass or more and 1% by mass or less in terms of molybdenum trioxide.
(7) The production method according to any one of (4) to (6), wherein a sodium compound or a potassium compound is used as a shape control agent during firing.
(8) The production method according to any one of (4) to (7), which comprises firing at less than 1300°C.
(9) The production method according to any one of (4) to (8), wherein the average particle diameter of the aluminum compound and the magnesium compound is 1 μm or more and 10 μm or less.
　上記態様の板状スピネル粒子及びその製造方法によれば、誘電正接を低く保ちながら、優れた機械強度を有する板状スピネル粒子を提供することができる。 According to the plate-like spinel particles and the method for producing the same in the above aspect, it is possible to provide plate-like spinel particles having excellent mechanical strength while maintaining a low dielectric loss tangent.
実施例及び比較例で得られたスピネル粒子のＳＥＭ画像である。（Ａ）～（Ｅ）のスケールバー（実線）は１０．０μｍである。（Ｆ）のスケールバー（点線）は５０．０μｍである。3 is an SEM image of spinel particles obtained in Examples and Comparative Examples. The scale bar (solid line) in (A) to (E) is 10.0 μm. The scale bar (dotted line) in (F) is 50.0 μm.
　以下、本発明の一実施形態に係る板状スピネル粒子及びその製造方法について詳細に説明する。 Hereinafter, the plate-like spinel particles and the manufacturing method thereof according to the embodiment of the present invention will be described in detail.
≪板状スピネル粒子≫
　実施形態に係る板状スピネル粒子は、厚みＴが０．０１μｍ以上５μｍ以下であり、平均粒子径Ｌが０．１μｍ以上５００μｍ以下であり、かつアスペクト比Ｌ／Ｔが３以上５００以下である。また、実施形態に係る板状スピネル粒子は、粒子内にモリブデンを含む。 <<Plate-shaped spinel particles>>
The plate-shaped spinel particles according to the embodiment have a thickness T of 0.01 μm or more and 5 μm or less, an average particle diameter L of 0.1 μm or more and 500 μm or less, and an aspect ratio L/T of 3 or more and 500 or less. Further, the plate-like spinel particles according to the embodiment include molybdenum in the particles.
　一般に、「スピネル粒子」は、マグネシウム原子、アルミニウム原子、及び酸素原子を含むことから、通常、ＭｇＡｌ２Ｏ４の化学組成で表される。実施形態に係る板状スピネル粒子は粒子内にモリブデンを含み、モリブデンの含有形態は特に制限されないが、モリブデンがスピネル粒子表面に付着、被覆、結合、その他これに類する形態で配置される形態、モリブデンがスピネルに組み込まれる形態、これらの組み合わせが挙げられる。この際、「モリブデンがスピネルに組み込まれる形態」としては、スピネル粒子を構成する原子の少なくとも一部がモリブデンに置換する形態、スピネル粒子の結晶内部に存在しうる空間（結晶構造の欠陥により生じる空間等を含む）にモリブデンが配置される形態等が挙げられる。なお、前記置換する形態において、置換されるスピネル粒子を構成する原子としては、特に制限されず、マグネシウム原子、アルミニウム原子、酸素原子、他の原子のいずれであってもよい。
　中でも、モリブデンは少なくともスピネルに組み込まれる形態で含有されることが好ましい。なお、モリブデンがスピネルに組み込まれている場合、例えば、洗浄による除去がされにくい傾向がある。 In general, "spinel particles" contain a magnesium atom, an aluminum atom, and an oxygen atom, and thus are usually represented by a chemical composition of MgAl 2 O 4 . The plate-like spinel particles according to the embodiment include molybdenum in the particles, the molybdenum containing form is not particularly limited, but molybdenum adheres to the surface of the spinel particles, coats, bonds, and forms similar to these, molybdenum. And a combination thereof. At this time, as the "form in which molybdenum is incorporated into the spinel", a form in which at least a part of atoms constituting the spinel particle is replaced with molybdenum, a space that may exist inside the crystal of the spinel particle (a space generated by a defect in the crystal structure And the like), and the like in which molybdenum is arranged. It should be noted that, in the substituting form, the atom constituting the spinel particle to be substituted is not particularly limited and may be a magnesium atom, an aluminum atom, an oxygen atom, or any other atom.
Among them, molybdenum is preferably contained at least in a form incorporated in spinel. When molybdenum is incorporated in the spinel, it tends to be difficult to be removed by cleaning, for example.
　実施形態に係る板状スピネル粒子は、上記形状であることにより、誘電正接を低く保ちながら、機械強度に優れるものとすることができる。従来のスピネル粒子は、後述する実施例にも示すように、上記厚み、平均粒子径及びアスペクト比のうち少なくともいずれか１つの要件を満たさないものであった。そのため、従来のスピネル粒子は、おそらく板状でないか、粒子サイズが小さいために、誘電正接は低いが、機械強度に乏しいものであった。
　実施形態に係る板状スピネル粒子は、特に、高アスペクト比であることから、優れた機械強度を発揮できるものと考えられる。 The plate-like spinel particles according to the embodiment can have excellent mechanical strength while maintaining a low dielectric loss tangent because of the above-mentioned shape. The conventional spinel particles did not satisfy at least one of the requirements of the thickness, average particle diameter and aspect ratio, as will be shown in Examples described later. Therefore, the conventional spinel particles have a low dielectric loss tangent but a poor mechanical strength, probably because they are not plate-like or have a small particle size.
Since the plate-like spinel particles according to the embodiment have a high aspect ratio, it is considered that they can exhibit excellent mechanical strength.
　本明細書において、「アスペクト比」とは、スピネル粒子の平均粒子径を厚みで除した比である。また、ここでいう「板状」とは、アスペクト比が２以上であることを指す。なお、本明細書において、「スピネル粒子の厚み」は、走査型電子顕微鏡（ＳＥＭ）により得られたイメージから、無作為に選出された少なくとも５０個のスピネル粒子について測定された厚みの算術平均値とする。「粒径」は、スピネル粒子の輪郭線上の２点間の距離のうち、最大の長さとする。「スピネル粒子の平均粒子径」は走査型電子顕微鏡（ＳＥＭ）により得られたイメージから、無作為に選出された少なくとも５０個の板状スピネル粒子について測定された粒径の算術平均値とする。 In the present specification, the “aspect ratio” is the ratio of the average particle diameter of spinel particles divided by the thickness. The term "plate-like" as used herein means that the aspect ratio is 2 or more. In the present specification, the "thickness of spinel particles" is the arithmetic mean value of the thickness measured for at least 50 spinel particles randomly selected from an image obtained by a scanning electron microscope (SEM). And The “particle diameter” is the maximum length of the distance between two points on the contour line of the spinel particle. The "average particle size of spinel particles" is the arithmetic mean value of the particle sizes measured for at least 50 plate-like spinel particles randomly selected from the images obtained by a scanning electron microscope (SEM).
　実施形態に係る板状スピネル粒子は、厚みが０．０１μｍ以上５μｍ以下であり、０．０５μｍ以上３μｍ以下が好ましく、０．１μｍ以上１μｍ以下がより好ましく、０．１５μｍ以上０．７５μｍ以下がさらに好ましく、０．２μｍ以上０．５μｍ以下が特に好ましく、０．２μｍ以上０．４７μｍ以下が最も好ましい。板状スピネル粒子の厚みが上記範囲内であることで、機械強度により優れたものとすることができる。 The plate-like spinel particles according to the embodiment have a thickness of 0.01 μm or more and 5 μm or less, preferably 0.05 μm or more and 3 μm or less, more preferably 0.1 μm or more and 1 μm or less, and further preferably 0.15 μm or more and 0.75 μm or less. It is particularly preferably 0.2 μm or more and 0.5 μm or less, and most preferably 0.2 μm or more and 0.47 μm or less. When the thickness of the plate-like spinel particles is within the above range, the mechanical strength can be made more excellent.
　実施形態に係る板状スピネル粒子は、平均粒子径が０．１μｍ以上５００μｍ以下であり、０．３μｍ以上１００μｍ以下が好ましく、０．５μｍ以上５０μｍ以下がより好ましく、１μｍ以上３０μｍ以下がさらに好ましく、１μｍ以上２０μｍ以下がよりさらに好ましく、１μｍ以上１０μｍ以下が特に好ましく、４μｍ以上９μｍ以下が最も好ましい。板状スピネル粒子の平均粒子径が上記下限値以上であることで、樹脂等と混合する場合に粘度の上昇をより効果的に抑制することができ、一方で、上記上限値以下であることで、板状スピネル粒子を含む成形品の表面をより平滑なものとすることができる。 The plate-like spinel particles according to the embodiment have an average particle size of 0.1 μm or more and 500 μm or less, preferably 0.3 μm or more and 100 μm or less, more preferably 0.5 μm or more and 50 μm or less, and further preferably 1 μm or more and 30 μm or less, It is more preferably 1 μm or more and 20 μm or less, particularly preferably 1 μm or more and 10 μm or less, and most preferably 4 μm or more and 9 μm or less. When the average particle diameter of the plate-like spinel particles is equal to or more than the lower limit value, it is possible to more effectively suppress an increase in viscosity when mixed with a resin or the like, while being equal to or less than the upper limit value. The surface of the molded product containing the plate-like spinel particles can be made smoother.
　実施形態に係る板状スピネル粒子は、アスペクト比が３以上５００以下であり、５以上１００以下が好ましく、７以上５０以下がより好ましく、９以上３０以下がさらに好ましく、１０以上２５以下がよりさらに好ましく、１２以上２３以下が特に好ましく、１４．５以上２０以下が最も好ましい。アスペクト比が上記下限値以上であることで、より機械強度に優れたものとなる傾向があり、一方で、上記上限値以下であることで、板状スピネル粒子を含む成形品の表面をより平滑なものとすることができる。 The plate-like spinel particles according to the embodiment have an aspect ratio of 3 or more and 500 or less, preferably 5 or more and 100 or less, more preferably 7 or more and 50 or less, still more preferably 9 or more and 30 or less, still more preferably 10 or more and 25 or less. It is preferably 12 or more and 23 or less, particularly preferably 14.5 or more and 20 or less. When the aspect ratio is equal to or more than the above lower limit, the mechanical strength tends to be more excellent, while when the aspect ratio is less than or equal to the above upper limit, the surface of the molded article containing the plate-like spinel particles becomes smoother. It can be anything.
　上記の好ましいスピネル粒子の形状について、厚み、平均粒子径、及びアスペクト比の条件は、それが板状である範囲で、どのように組み合わせることもできる。 Regarding the above preferable spinel particle shape, the conditions of thickness, average particle diameter, and aspect ratio can be combined in any manner as long as it is in a plate shape.
　実施形態に係る板状スピネル粒子は、円形板状や楕円形板状であってもよいが、粒子形状は、例えば、六角～八角といった多角板状であることが、誘電正接等の特性や、取り扱い性、製造のし易さ等の点から好ましい。 The plate-shaped spinel particles according to the embodiment may have a circular plate shape or an elliptical plate shape, but the particle shape is, for example, a polygonal plate shape such as hexagonal to octagonal, which has characteristics such as dielectric loss tangent and It is preferable from the viewpoints of handleability and ease of production.
　実施形態に係る板状スピネル粒子の（３１１）面の結晶子径は、６０ｎｍ以上が好ましく、６５ｎｍ以上がより好ましく、６６ｎｍ以上がさらに好ましく、７０ｎｍ以上がよりさらに好ましい。一方で、（３１１）面の結晶子径の上限は特別な限定はなく、例えば、２００ｎｍ以下とすることができ、１５０ｎｍ以下とすることができ、１００ｎｍ以下とすることができ、９０ｎｍ以下とすることができ、８２ｎｍ以下とすることができる。
　ここで、（３１１）面はスピネル粒子の主要な結晶ドメインの１つであり、当該（３１１）面の結晶ドメインの大きさが（３１１）面の結晶子径に相当する。当該結晶子径が大きいほど粒子の緻密性及び結晶性が高く、フォノンの散乱が起こる乱れ部分がないことを意味するため、熱伝導性が高いということができる。なお、スピネル粒子の（３１１）面の結晶子径は、後述する製造方法の条件を適宜設定することで制御することができる。また、本明細書において「（３１１）面の結晶子径」の値は、Ｘ線回折（ＸＲＤ）を用いて測定された（３１１）面に帰属されるピーク（２θ＝３７度付近に出現するピーク）の半値幅からシェラー式を用いて算出された値を採用するものとする。なお、ここでいう「３７度付近」とは、３７度±０．５度の範囲を意味する。 The crystallite diameter of the (311) plane of the plate-like spinel particles according to the embodiment is preferably 60 nm or more, more preferably 65 nm or more, even more preferably 66 nm or more, even more preferably 70 nm or more. On the other hand, the upper limit of the crystallite diameter of the (311) plane is not particularly limited and can be, for example, 200 nm or less, 150 nm or less, 100 nm or less, and 90 nm or less. And can be 82 nm or less.
Here, the (311) plane is one of the main crystal domains of the spinel particle, and the size of the crystal domain of the (311) plane corresponds to the crystallite diameter of the (311) plane. The larger the crystallite diameter, the higher the particle density and crystallinity, which means that there is no disordered portion where phonon scattering occurs. Therefore, it can be said that the thermal conductivity is high. The crystallite size of the (311) plane of the spinel particles can be controlled by appropriately setting the conditions of the manufacturing method described later. In addition, in the present specification, the value of “crystallite diameter of (311) plane” appears in the peak (2θ=37 degrees or so) attributed to the (311) plane measured by X-ray diffraction (XRD). The value calculated using the Scherrer formula from the half-width of the (peak) shall be adopted. The term “near 37 degrees” as used herein means a range of 37 degrees ±0.5 degrees.
　上述のとおりスピネル粒子は、マグネシウム原子、アルミニウム原子、及び、酸素原子を含み、一般的には、ＭｇＡｌ２Ｏ４の組成で表される。また、実施形態に係る板状スピネル粒子は、モリブデンを含む。また、実施形態に係る板状スピネル粒子は、本発明の効果を損なわない限り、その他、不可避不純物、他の原子等が含まれていてもよい。 As described above, the spinel particles contain magnesium atoms, aluminum atoms, and oxygen atoms, and are generally represented by the composition of MgAl 2 O 4 . Further, the plate-like spinel particles according to the embodiment contain molybdenum. Further, the plate-like spinel particles according to the embodiment may contain other unavoidable impurities, other atoms, etc. as long as the effects of the present invention are not impaired.
＜各原子の含有量＞
　スピネル粒子中のマグネシウム原子の含有量は、特に制限されないが、例えば、アルミニウム原子のモル量が２モルである場合、０．８モル以上１．２モル以下であることが好ましく、０．９モル以上１．１モル以下であることがより好ましい。
　スピネル粒子中のアルミニウム原子の含有量は、特に制限されないが、例えば、マグネシウム原子のモル量を１モルとした場合、１．８モル以上２．２モル以下であることが好ましく、１．９モル以上２．１モル以下であることがより好ましい。
　なお、スピネル粒子中のマグネシウム原子及びアルミニウム原子の含有量は誘導結合プラズマ発光分光分析法（ＩＣＰ－ＡＥＳ）により測定することができる。
　スピネル粒子中の酸素原子の含有量は、特に制限されないが、マグネシウム原子及びアルミニウム原子のモル量に応じて決まる。例えば、マグネシウム原子及びアルミニウム原子がそれぞれ１モルと２モルである場合、スピネル粒子中の酸素原子の含有量は、３．８モル以上４．２モル以下であることが好ましく、３．９モル以上４．１モル以下であることがより好ましい。 <Content of each atom>
The content of magnesium atoms in the spinel particles is not particularly limited, but for example, when the molar amount of aluminum atoms is 2 mol, it is preferably 0.8 mol or more and 1.2 mol or less, and 0.9 mol or less. More preferably, it is 1.1 mol or less.
The content of aluminum atoms in the spinel particles is not particularly limited, but for example, when the molar amount of magnesium atoms is 1 mol, it is preferably 1.8 mol or more and 2.2 mol or less, and 1.9 mol. More preferably, it is 2.1 mol or less.
The content of magnesium atoms and aluminum atoms in the spinel particles can be measured by inductively coupled plasma optical emission spectroscopy (ICP-AES).
The content of oxygen atoms in the spinel particles is not particularly limited, but depends on the molar amount of magnesium atoms and aluminum atoms. For example, when the magnesium atom and the aluminum atom are 1 mol and 2 mol, respectively, the content of oxygen atoms in the spinel particles is preferably 3.8 mol or more and 4.2 mol or less, and preferably 3.9 mol or more. It is more preferably 4.1 mol or less.
＜モリブデン＞
　モリブデンは、後述する製造方法に起因して含有されうる。 <Molybdenum>
Molybdenum may be contained due to the manufacturing method described below.
　当該モリブデンとしては、特に制限されないが、モリブデン金属の他、酸化モリブデンや一部が還元されたモリブデン化合物等が含まれる。モリブデンは、ＭｏＯ３として板状スピネル粒子に含まれると考えられるが、ＭｏＯ３以外にもＭｏＯ２やＭｏＯ等として板状スピネル粒子に含まれてもよい。 The molybdenum is not particularly limited, but includes molybdenum metal, molybdenum oxide, a partially reduced molybdenum compound, and the like. Molybdenum is considered to be included in the plate-shaped spinel particles as MoO 3, it may be included in the plate-shaped spinel particles as MoO 2 and MoO like in addition to MoO 3.
　モリブデンの含有形態は、特に制限されず、板状スピネル粒子の表面に付着、被覆、結合、その他これに類する形態で配置される形態で含まれていてもよく、モリブデンがスピネルに組み込まれる形態で含まれていてもよく、これらの組み合わせであってもよい。 The contained form of molybdenum is not particularly limited, and may be contained in the form of being adhered, coated, bonded, or the like on the surface of the plate-like spinel particles, or in a form in which molybdenum is incorporated into the spinel. It may be contained or a combination thereof.
　モリブデンの含有量は、特に制限されないが、実施形態に係る板状スピネル粒子の高熱伝導性の観点から、板状スピネル粒子１００質量％に対して、三酸化モリブデン換算で１質量％以下であることが好ましく、０．８質量％以下であることがより好ましく、板状スピネル粒子がより高い緻密性を示す観点から、０．７質量％以下であることがさらに好ましく、０．６５質量％以下がよりさらに好ましく、０．６１質量％以下が特に好ましい。一方で、モリブデンの含有量の下限は特に限定されないが、例えば０．０１質量以上とすることができ、０．０５質量％以上とすることができ、０．１質量％以上とすることができ、０．１５質量％以上とすることができ、０．２質量％以上とすることができ、０．２５質量％以上とすることができ、０．３１質量％以上とすることができる。なお、本明細書において、板状スピネル粒子中のモリブデンの含有量は、ＸＲＦ分析により求めることができる。ＸＲＦ分析は、後述する実施例に記載の測定条件と同一の条件、又は同一の測定結果が得られる互換性のある条件のもと実施されるものとする。 The content of molybdenum is not particularly limited, but from the viewpoint of high thermal conductivity of the plate-shaped spinel particles according to the embodiment, it should be 1% by mass or less in terms of molybdenum trioxide with respect to 100% by mass of the plate-shaped spinel particles. Is more preferable, 0.8% by mass or less is more preferable, from the viewpoint that the plate-shaped spinel particles exhibit higher density, 0.7% by mass or less is more preferable, and 0.65% by mass or less is It is even more preferable, and 0.61% by mass or less is particularly preferable. On the other hand, the lower limit of the content of molybdenum is not particularly limited, but can be, for example, 0.01 mass% or more, 0.05 mass% or more, and 0.1 mass% or more. , 0.15 mass% or more, 0.2 mass% or more, 0.25 mass% or more, and 0.31 mass% or more. In this specification, the content of molybdenum in the plate-like spinel particles can be obtained by XRF analysis. The XRF analysis is performed under the same measurement conditions as those described in Examples described later or under compatible conditions that the same measurement results are obtained.
＜不可避不純物＞
　不可避不純物は、原料中に存在したり、製造工程において不可避的に板状スピネル粒子に混入するものであり、本来は不要なものであるが、微量であり、板状スピネル粒子の特性に影響を及ぼさない不純物を意味する。 <Inevitable impurities>
The unavoidable impurities are present in the raw materials or are inevitably mixed in the plate-shaped spinel particles in the manufacturing process, and are essentially unnecessary, but they are in small amounts and affect the properties of the plate-shaped spinel particles. Means impurities that do not extend.
　不可避不純物としては、特に制限されないが、ケイ素、鉄、カリウム、ナトリウム、カルシウム等が挙げられる。これらの不可避不純物は単独で含まれていても、２種以上が含まれていてもよい。 The unavoidable impurities include, but are not limited to, silicon, iron, potassium, sodium, calcium and the like. These unavoidable impurities may be contained alone or in combination of two or more.
　板状スピネル粒子中の不可避不純物の含有量は、板状スピネル粒子の質量に対して、１００００ｐｐｍ以下であることが好ましく、１０００ｐｐｍ以下であることがより好ましく、１０ｐｐｍ以上５００ｐｐｍ以下であることがさらに好ましい。 The content of unavoidable impurities in the plate-like spinel particles is preferably 10000 ppm or less, more preferably 1000 ppm or less, and further preferably 10 ppm or more and 500 ppm or less, based on the mass of the plate-like spinel particles. ..
＜他の原子＞
　他の原子は、本発明の効果を阻害しない範囲において、着色、発光、スピネル粒子の形成制御等を目的として意図的にスピネル粒子に添加されるものを意味する。 <Other atoms>
The other atom means one that is intentionally added to the spinel particles for the purpose of coloring, emitting light, controlling the formation of spinel particles, etc. within a range that does not impair the effects of the present invention.
　他の原子としては、特に制限されないが、亜鉛、コバルト、ニッケル、鉄、マンガン、チタン、ジルコニウム、カルシウム、ストロンチウム、イットリウム等が挙げられる。これらの他の原子は単独で用いてもよく、２種以上を混合して用いてもよい。 Other atoms include, but are not limited to, zinc, cobalt, nickel, iron, manganese, titanium, zirconium, calcium, strontium, yttrium, and the like. These other atoms may be used alone or in combination of two or more.
　板状スピネル粒子中の他の原子の含有量は、板状スピネル粒子１００質量％に対して、１０質量％以下であることが好ましく、５質量％以下であることがより好ましく、２質量％以下であることがさらに好ましい。 The content of other atoms in the plate-shaped spinel particles is preferably 10% by mass or less, more preferably 5% by mass or less, and 2% by mass or less, relative to 100% by mass of the plate-shaped spinel particles. Is more preferable.
≪板状スピネル粒子の製造方法≫
　実施形態に係る板状スピネル粒子の製造方法は、特に限定されず、公知の技術が適宜適用され得るが、マグネシウム化合物及びアルミニウム化合物を、モリブデン存在下で、焼成させる工程（焼成工程）を含む製造方法が好ましい。焼成工程は焼成対象の混合物を得る工程（混合工程）で得られた混合物を焼成する工程であってもよい。 <<Method for producing plate-like spinel particles>>
The method for producing the plate-like spinel particles according to the embodiment is not particularly limited, and known techniques may be appropriately applied, but the method includes a step of firing a magnesium compound and an aluminum compound in the presence of molybdenum (firing step). The method is preferred. The firing step may be a step of firing the mixture obtained in the step of obtaining the mixture to be fired (mixing step).
＜混合工程＞
　混合工程は、マグネシウム化合物、アルミニウム化合物、モリブデン等の原料を混合して混合物とする工程である。この際、マグネシウム化合物及びアルミニウム化合物の混合状態は、特に限定されない。両者を混合する場合には、粉体を混ぜ合わせる簡便な混合、粉砕機やミキサー等を用いた機械的な混合、乳鉢等を用いた混合等が行われる。この際、得られる混合物は、乾式状態、湿式状態のいずれであってもよいが、コストの観点から乾式状態であることが好ましい。 <Mixing process>
The mixing step is a step of mixing raw materials such as a magnesium compound, an aluminum compound and molybdenum to obtain a mixture. At this time, the mixed state of the magnesium compound and the aluminum compound is not particularly limited. When both are mixed, simple mixing for mixing powders, mechanical mixing using a crusher or mixer, mixing using a mortar or the like is performed. At this time, the obtained mixture may be in a dry state or a wet state, but is preferably in a dry state from the viewpoint of cost.
　混合工程において、マグネシウム化合物とアルミニウム化合物との混合比は特別な限定はないが、マグネシウム化合物のマグネシウム元素に対するアルミニウム化合物のアルミニウム元素のモル比（アルミニウム元素／マグネシウム元素）が、１．８以上２．２以下となるように混合することが好ましく、１．９以上２．１以下となるように混合することがより好ましい。
　以下、混合物の内容について説明する。 In the mixing step, the mixing ratio of the magnesium compound and the aluminum compound is not particularly limited, but the molar ratio of the aluminum element of the aluminum compound to the magnesium element of the magnesium compound (aluminum element/magnesium element) is 1.8 or more.2. It is preferable to mix so as to be 2 or less, and it is more preferable to mix so as to be 1.9 or more and 2.1 or less.
The contents of the mixture will be described below.
［マグネシウム化合物］
　マグネシウム化合物としては、特に制限されないが、金属マグネシウム、マグネシウム誘導体、マグネシウムオキソ酸塩、マグネシウム有機塩、及びこれらの水和物等が挙げられる。マグネシウム誘導体としては、例えば、酸化マグネシウム、水酸化マグネシウム、過酸化マグネシウム、フッ化マグネシウム、塩化マグネシウム、臭化マグネシウム、ヨウ化マグネシウム、水素化マグネシウム、二ホウ化マグネシウム、窒化マグネシウム、硫化マグネシウム等が挙げられる。マグネシウムオキソ酸塩としては、例えば、炭酸マグネシウム、炭酸カルシウムマグネシウム、硝酸マグネシウム、硫酸マグネシウム、亜硫酸マグネシウム、過塩素酸マグネシウム、リン酸三マグネシウム、過マンガン酸マグネシウム、リン酸マグネシウム等が挙げられる。マグネシウム有機塩としては、例えば、酢酸マグネシウム、クエン酸マグネシウム、リンゴ酸マグネシウム、グルタミン酸マグネシウム、安息香酸マグネシウム、ステアリン酸マグネシウム、アクリル酸マグネシウム、メタクリル酸マグネシウム、グルコン酸マグネシウム、ナフテン酸マグネシウム、サリチル酸マグネシウム、乳酸マグネシウム、モノペルオキシフタル酸マグネシウム等が挙げられる。なお、これらマグネシウム化合物は単独で用いてもよく、２種以上を組み合わせて用いてもよい。
　中でも、酸化マグネシウム、水酸化マグネシウム、炭酸マグネシウム、酢酸マグネシウム、硝酸マグネシウム又は硫酸マグネシウムであることが好ましく、酸化マグネシウム、水酸化マグネシウム、硝酸マグネシウム又は酢酸マグネシウムであることがより好ましい。 [Magnesium compound]
The magnesium compound is not particularly limited, but examples thereof include metallic magnesium, magnesium derivatives, magnesium oxo acid salts, magnesium organic salts, and hydrates thereof. Examples of the magnesium derivative include magnesium oxide, magnesium hydroxide, magnesium peroxide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, magnesium hydride, magnesium diboride, magnesium nitride and magnesium sulfide. To be Examples of the magnesium oxo acid salt include magnesium carbonate, calcium magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium sulfite, magnesium perchlorate, trimagnesium phosphate, magnesium permanganate, magnesium phosphate and the like. As the magnesium organic salt, for example, magnesium acetate, magnesium citrate, magnesium malate, magnesium glutamate, magnesium benzoate, magnesium stearate, magnesium acrylate, magnesium methacrylate, magnesium gluconate, magnesium naphthenate, magnesium salicylate, lactic acid. Examples thereof include magnesium and magnesium monoperoxyphthalate. These magnesium compounds may be used alone or in combination of two or more.
Among them, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium acetate, magnesium nitrate or magnesium sulfate is preferable, and magnesium oxide, magnesium hydroxide, magnesium nitrate or magnesium acetate is more preferable.
　マグネシウム化合物の平均粒子径は、特に限定されないが、１μｍ以上１０μｍ以下が好ましく、１．５μｍ以上５μｍ以下がより好ましく、２μｍ以上４μｍ以下がさらに好ましく、２．５μｍ以上３．５μｍ以上が特に好ましい。マグネシウム化合物の平均粒子径が上記下限値以上であると、スピネル結晶化において粒子凝集をより効果的に防止し得る。一方、マグネシウム化合物の平均粒子径が上記上限値以下であると、スピネル結晶化が粒子の中心部までより効率よく進行し得る。 The average particle diameter of the magnesium compound is not particularly limited, but is preferably 1 μm or more and 10 μm or less, more preferably 1.5 μm or more and 5 μm or less, further preferably 2 μm or more and 4 μm or less, and particularly preferably 2.5 μm or more and 3.5 μm or more. When the average particle diameter of the magnesium compound is not less than the above lower limit, particle aggregation can be more effectively prevented in spinel crystallization. On the other hand, when the average particle diameter of the magnesium compound is not more than the above upper limit value, spinel crystallization can proceed to the central portion of the particles more efficiently.
　マグネシウム化合物は市販品を使用してもよく、自ら調製してもよい。
　マグネシウム化合物を自ら調製する場合、反応性を調整することができる。例えば、マグネシウムイオンの酸性水溶液を塩基で中和することで粒子径の小さい水酸化マグネシウムを得ることができる。得られる粒径の小さい水酸化マグネシウムは反応性が高いため、これを用いて得られるスピネルの結晶子径は大きくなる傾向がある。 The magnesium compound may be a commercially available product or may be prepared by itself.
When the magnesium compound is prepared by itself, the reactivity can be adjusted. For example, magnesium hydroxide having a small particle size can be obtained by neutralizing an acidic aqueous solution of magnesium ions with a base. Since the obtained magnesium hydroxide having a small particle size has high reactivity, the crystallite size of the spinel obtained using this tends to be large.
［アルミニウム化合物］
　アルミニウム化合物としては、特に限定されないが、アルミニウム金属、塩化アルミニウム、硫酸アルミニウム、塩基性酢酸アルミニウム、水酸化アルミニウム、ベーマイト、擬ベーマイト、酸化アルミニウム等が挙げられる。酸化アルミニウムとしては、例えば、酸化アルミニウム水和物、β－酸化アルミニウム、γ－酸化アルミニウム、δ－酸化アルミニウム、θ－酸化アルミニウム、α－酸化アルミニウム、２種以上の結晶相を有する混合酸化アルミニウム等が挙げられる。 [Aluminum compound]
The aluminum compound is not particularly limited, but examples thereof include aluminum metal, aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, and aluminum oxide. Examples of aluminum oxide include hydrated aluminum oxide, β-aluminum oxide, γ-aluminum oxide, δ-aluminum oxide, θ-aluminum oxide, α-aluminum oxide, and mixed aluminum oxide having two or more crystal phases. Are listed.
　上述のアルミニウム化合物は、酸化アルミニウムであることが好ましく、α結晶、β結晶、γ結晶、δ結晶及びθ結晶からなる群から選択される少なくとも１つの結晶形態を有する酸化アルミニウムであることが好ましく、α結晶を有する酸化アルミニウムであることがより好ましい。 The above-mentioned aluminum compound is preferably aluminum oxide, preferably aluminum oxide having at least one crystal form selected from the group consisting of α crystal, β crystal, γ crystal, δ crystal and θ crystal, Aluminum oxide having α crystals is more preferable.
　また、上述のアルミニウム化合物はモリブデンを含むことが好ましい。この際、前記モリブデンを含むアルミニウム化合物のモリブデン含有形態は、特に制限されないが、スピネル粒子と同様に、モリブデンがアルミニウム化合物表面に付着、被覆、結合、その他これに類する形態で配置される形態、モリブデンがアルミニウム化合物に組み込まれる形態、これらの組み合わせが挙げられる。この際、「モリブデンがアルミニウム化合物に組み込まれる形態」としては、アルミニウム化合物を構成する原子の少なくとも一部がモリブデンに置換する形態、アルミニウム化合物の結晶内部に存在しうる空間（結晶構造の欠陥により生じる空間等を含む）にモリブデンが配置される形態等が挙げられる。なお、前記置換する形態において、置換されるアルミニウム化合物を構成する原子としては、特に制限されず、アルミニウム原子、酸素原子、他の原子のいずれであってもよい。 Also, the above-mentioned aluminum compound preferably contains molybdenum. At this time, the molybdenum-containing form of the aluminum compound containing molybdenum is not particularly limited, but like the spinel particles, molybdenum is attached to the surface of the aluminum compound, coated, bonded, or arranged in a form similar thereto, molybdenum. And a combination thereof. At this time, as the “form in which molybdenum is incorporated into the aluminum compound”, a form in which at least a part of atoms constituting the aluminum compound is substituted with molybdenum, a space that may exist inside the crystal of the aluminum compound (occurs due to a defect in the crystal structure) A form in which molybdenum is arranged in (including a space) is included. In the substituting form, the atoms constituting the aluminum compound to be substituted are not particularly limited and may be any of aluminum atoms, oxygen atoms and other atoms.
　上述のアルミニウム化合物のうち、モリブデンを含むアルミニウム化合物を用いることが好ましく、モリブデンが組み込まれたアルミニウム化合物を用いることがより好ましい。 Among the above-mentioned aluminum compounds, it is preferable to use an aluminum compound containing molybdenum, and it is more preferable to use an aluminum compound containing molybdenum.
　モリブデンを含むアルミニウム化合物が好ましい理由は必ずしも明らかではないが、以下のメカニズムによるものと推察される。すなわち、アルミニウム化合物に含まれるモリブデンが固相界面における核形成の促進、アルミニウム原子とマグネシウム原子の固相拡散の促進等の機能を果たし、アルミニウム化合物とマグネシウム化合物との固相反応がより好適に進行するものと考えられる。すなわち、後述するように、モリブデンを含むアルミニウム化合物は、アルミニウム化合物、かつ、モリブデンとしての機能を有しうるのである。特に、モリブデンが組み込まれたアルミニウム化合物は、反応点に直接又は近接した部分にモリブデンが配置されることとなり、モリブデンによる効果をより効果的に発揮しうる。なお、上記メカニズムはあくまで推測のものであり、上記メカニズムと異なるメカニズムで所望の効果が得られる場合であっても、技術的範囲に含まれる。 The reason why an aluminum compound containing molybdenum is preferable is not clear, but it is presumed that it is due to the following mechanism. That is, molybdenum contained in the aluminum compound plays a role of promoting nucleation at the solid phase interface, promoting solid phase diffusion of aluminum atoms and magnesium atoms, etc., so that the solid phase reaction between the aluminum compound and magnesium compound proceeds more favorably. It is supposed to do. That is, as described later, the aluminum compound containing molybdenum can have a function as an aluminum compound and molybdenum. In particular, in an aluminum compound incorporating molybdenum, molybdenum is arranged directly or in the vicinity of the reaction point, and the effect of molybdenum can be more effectively exhibited. It should be noted that the above mechanism is only an estimation, and even if a desired effect can be obtained by a mechanism different from the above mechanism, it is included in the technical scope.
　アルミニウム化合物の形状については特に限定されないが、多面体状、球状、楕円状、円柱状、多角柱状、針状、棒状、板状、円板状、薄片状、鱗片状等が挙げられる。中でも、後述において説明するとおり、実施形態に係る製造方法では、アルミニウム化合物の形状を反映したスピネル粒子が得られる傾向があることから、板状であることが好ましい。 The shape of the aluminum compound is not particularly limited, and examples thereof include polyhedron, sphere, ellipse, column, polygonal column, needle, rod, plate, disc, flakes, and scales. Among them, as described below, the manufacturing method according to the embodiment tends to obtain spinel particles that reflect the shape of the aluminum compound, and thus the plate shape is preferable.
　アルミニウム化合物の平均粒子径は、特に限定されないが、得たい板状スピネルの粒子径に応じ適宜調整する。アルミニウム化合物の平均粒子径は、０．１μｍ以上５００μｍ以下であり、０．３μｍ以上１００μｍ以下が好ましく、０．５μｍ以上５０μｍ以下がより好ましく、１μｍ以上３０μｍ以下がさらに好ましく、１μｍ以上２０μｍ以下がよりさらに好ましく、１μｍ以上１０μｍ以下が特に好ましく、３．８μｍ以上７．０μｍ以下が最も好ましい。アルミニウム化合物の平均粒子径が上記下限値以上であると、スピネル結晶化において粒子凝集をより効果的に防止し得る。一方、アルミニウム化合物の平均粒子径が上記上限値以下であると、スピネル結晶化が粒子の中心部までより効率よく進行し得る。 The average particle size of the aluminum compound is not particularly limited, but it is appropriately adjusted according to the particle size of the plate-like spinel to be obtained. The average particle size of the aluminum compound is 0.1 μm or more and 500 μm or less, preferably 0.3 μm or more and 100 μm or less, more preferably 0.5 μm or more and 50 μm or less, further preferably 1 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. More preferably, it is particularly preferably 1 μm or more and 10 μm or less, most preferably 3.8 μm or more and 7.0 μm or less. When the average particle diameter of the aluminum compound is at least the above lower limit value, particle aggregation can be more effectively prevented in spinel crystallization. On the other hand, when the average particle diameter of the aluminum compound is not more than the above upper limit value, spinel crystallization can proceed more efficiently to the central portion of the particles.
　また、アルミニウム化合物の厚みは０．０１μｍ以上５μｍ以下であり、０．０５μｍ以上３μｍ以下が好ましく、０．１μｍ以上１μｍ以下がより好ましく、０．１５μｍ以上０．７５μｍ以下がさらに好ましく、０．２μｍ以上０．５μｍ以下が特に好ましい。アルミニウム化合物の厚みが上記範囲内であることで、アスペクト比のより大きい板状スピネル粒子を得ることができる。 The thickness of the aluminum compound is 0.01 μm or more and 5 μm or less, preferably 0.05 μm or more and 3 μm or less, more preferably 0.1 μm or more and 1 μm or less, still more preferably 0.15 μm or more and 0.75 μm or less, and 0.2 μm. Above 0.5 μm is particularly preferable. When the thickness of the aluminum compound is within the above range, plate-like spinel particles having a larger aspect ratio can be obtained.
　また、アルミニウム化合物のアスペクト比は３以上５００以下であり、５以上１００以下が好ましく、７以上５０以下がより好ましく、９以上３０以下がさらに好ましく、１０以上２５以下が特に好ましい。アスペクト比が上記下限値以上であることで、より機械強度に優れた板状スピネル粒子が得られ、一方で、上記上限値以下であることで、表面がより平滑な成形品や塗膜が得られる板状スピネル粒子となる。 Further, the aspect ratio of the aluminum compound is 3 or more and 500 or less, preferably 5 or more and 100 or less, more preferably 7 or more and 50 or less, further preferably 9 or more and 30 or less, and particularly preferably 10 or more and 25 or less. When the aspect ratio is the above lower limit or more, plate-like spinel particles having more excellent mechanical strength can be obtained, while when the aspect ratio is not more than the above upper limit, a molded article or coating film having a smoother surface can be obtained. It becomes plate-like spinel particles that can be used.
　アルミニウム化合物は、市販品を使用してもよいし、自ら調製したものを使用してもよい。アルミニウム化合物を自ら調製する場合、例えば、モリブデンを含むアルミニウム化合物は、以下に詳述するフラックス法により調製することができる。すなわち、好ましい一実施形態において、スピネル粒子の製造方法は、フラックス法によりアルミニウム化合物を調製する工程をさらに含む。 As the aluminum compound, a commercially available product may be used, or an aluminum compound prepared by itself may be used. When the aluminum compound is prepared by itself, for example, the aluminum compound containing molybdenum can be prepared by the flux method described in detail below. That is, in a preferred embodiment, the method for producing spinel particles further includes the step of preparing an aluminum compound by the flux method.
　フラックス法は、上述した固相法とは異なり、液相法、中でも溶液法に分類される。フラックス法とは、より詳細には、結晶－フラックス２成分系状態図が共晶型を示すことを利用した結晶成長の方法である。フラックス法のメカニズムとしては、以下のとおりであると推測される。すなわち、溶質及びフラックスの混合物を加熱していくと、溶質及びフラックスは液相となる。この際、フラックスは融剤であるため、換言すれば、溶質－フラックス２成分系状態図が共晶型を示すため、溶質は、その融点よりも低い温度で溶融し、液相を構成することとなる。この状態で、フラックスを蒸発させると、フラックスの濃度は低下し、換言すれば、フラックスによる前記溶質の融点低下効果が低減し、フラックスの蒸発が駆動力となって溶質の結晶成長が起こる（フラックス蒸発法）。なお、溶質及びフラックスは液相を冷却することによっても溶質の結晶成長を起こすことができる（徐冷法）。 The flux method, unlike the solid-phase method described above, is classified into the liquid-phase method, especially the solution method. More specifically, the flux method is a crystal growth method that utilizes the fact that the crystal-flux binary system phase diagram shows a eutectic type. The mechanism of the flux method is presumed to be as follows. That is, as the mixture of solute and flux is heated, the solute and flux become a liquid phase. At this time, since the flux is a flux, in other words, since the solute-flux binary system phase diagram shows a eutectic type, the solute should be melted at a temperature lower than its melting point to form a liquid phase. Becomes When the flux is evaporated in this state, the concentration of the flux is lowered, in other words, the melting point lowering effect of the solute by the flux is reduced, and the flux evaporation serves as a driving force to cause solute crystal growth (flux). Evaporation method). The solute and the flux can also cause solute crystal growth by cooling the liquid phase (slow cooling method).
　フラックス法は、融点よりもはるかに低い温度で結晶成長をさせることができる、結晶構造を精密に制御できる、自形をもつ多面体結晶体を形成できる等のメリットを有する。 The flux method has the advantages that crystals can be grown at a temperature much lower than the melting point, the crystal structure can be precisely controlled, and polyhedral crystals having an automorphism can be formed.
　アルミニウム化合物をフラックス法で調製する場合において、フラックス剤としてモリブデン化合物を使用すると、中間化合物であるモリブデン酸アルミニウムを経由して、モリブデンを含むアルミニウム化合物が得られ得る。この際、アルミニウム化合物に含まれるモリブデンは、フラックス法のデメリットと言われるフラックス不純物に該当しうるが、上述のように、本発明の一実施形態においてはアルミニウム化合物に含有されるモリブデンは、板状スピネル粒子を製造する際に好適な作用効果を発揮しうる。 When a molybdenum compound is used as the fluxing agent when preparing an aluminum compound by the flux method, an aluminum compound containing molybdenum can be obtained via the intermediate compound aluminum molybdate. At this time, molybdenum contained in the aluminum compound may correspond to a flux impurity which is said to be a disadvantage of the flux method. However, as described above, in one embodiment of the present invention, the molybdenum contained in the aluminum compound is plate-shaped. A suitable effect can be exhibited when producing spinel particles.
（フラックス蒸発法）
　一実施形態において、フラックス法は、アルミニウム源及びモリブデン化合物を含む混合物を焼成するフラックス蒸発工程と、前記焼成工程で結晶成長したアルミニウム化合物を冷却する冷却工程と、を含む。 (Flux evaporation method)
In one embodiment, the flux method includes a flux evaporation step of firing a mixture containing an aluminum source and a molybdenum compound, and a cooling step of cooling the aluminum compound crystal-grown in the firing step.
・アルミニウム源
　アルミニウム源としては、特に限定されないが、塩化アルミニウム、硫酸アルミニウム、塩基性酢酸アルミニウム、水酸化アルミニウム、ベーマイト、擬ベーマイト、遷移アルミナ、アルミナ水和物、α－アルミナ、２種以上の結晶相を有する混合アルミナ等が挙げられる。遷移アルミナとしては、例えば、γ－アルミナ、δ－アルミナ、θ－アルミナ等が挙げられる。なお、上述のアルミニウム源は単独で用いても、２種以上を組み合わせて用いてもよい。中でも、水酸化アルミニウム、遷移アルミナ、ベーマイト、擬ベーマイト又はアルミナ水和物であることが好ましく、水酸化アルミニウム、遷移アルミナ又はベーマイトであることがより好ましい。 Aluminum Source The aluminum source is not particularly limited, but aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, transition alumina, alumina hydrate, α-alumina, and two or more crystals. Examples include mixed alumina having a phase. Examples of the transition alumina include γ-alumina, δ-alumina, θ-alumina and the like. The above aluminum sources may be used alone or in combination of two or more. Among them, aluminum hydroxide, transition alumina, boehmite, pseudo-boehmite or alumina hydrate is preferable, and aluminum hydroxide, transition alumina or boehmite is more preferable.
　アルミニウム源は市販品を使用しても、自ら調製してもよい。
　アルミニウム源を自ら調製する場合、例えば、高温において構造安定性の高いアルミナ水和物又は遷移アルミナは、アルミニウムの水溶液の中和により調製することができる。より詳細には、前記アルミナ水和物は、アルミニウムの酸性水溶液を塩基で中和することで調製することができ、前記遷移アルミナは、上記で得られたアルミナ水和物を熱処理して調製することができる。なお、これによって得られるアルミナ水和物又は遷移アルミナは、高温において構造安定性が高いため、モリブデンの存在下で焼成すると、平均粒子径の大きいモリブデンを含むアルミニウム化合物が得られる傾向がある。 The aluminum source may be a commercially available product or may be prepared by itself.
When the aluminum source is prepared by itself, for example, alumina hydrate or transition alumina having high structural stability at high temperature can be prepared by neutralizing an aqueous solution of aluminum. More specifically, the alumina hydrate can be prepared by neutralizing an acidic aqueous solution of aluminum with a base, and the transition alumina is prepared by heat-treating the alumina hydrate obtained above. be able to. The alumina hydrate or transition alumina thus obtained has high structural stability at high temperatures, and therefore, when calcined in the presence of molybdenum, an aluminum compound containing molybdenum having a large average particle diameter tends to be obtained.
　上述したフラックス法において、アルミニウム源の形状は、特に制限されず、球状、無定形、アスペクトのある構造体、シート等のいずれであっても好適に用いることができる。アスペクトのある構造体としては、例えば、ワイヤ、ファイバー、リボン、チューブ等の形状のものであっても好適に用いることができる。 In the above-mentioned flux method, the shape of the aluminum source is not particularly limited, and any shape such as spherical, amorphous, structural body with aspect, sheet, etc. can be preferably used. As the structure having an aspect, for example, a wire, a fiber, a ribbon, a tube, or the like can be preferably used.
　同様に、上述したフラックス法において、アルミニウム源の粒子径は特に制限されず、数ｎｍから数百μｍまでのアルミニウム化合物の固体を好適に用いることができる。 Similarly, in the above-mentioned flux method, the particle size of the aluminum source is not particularly limited, and a solid aluminum compound of several nm to several hundreds of μm can be preferably used.
　また、アルミニウム源は、有機化合物と複合体を形成していてもよい。当該複合体としては、例えば、有機シランを用いて、アルミニウム化合物を修飾して得られる有機無機複合体、ポリマーを吸着したアルミニウム化合物複合体、有機化合物で被覆した複合体等が挙げられる。これらの複合体を用いる場合、有機化合物の含有率としては、特に制限はないが、６０質量％以下であることが好ましく、３０質量％以下であることがより好ましい。 Also, the aluminum source may form a complex with an organic compound. Examples of the composite include an organic-inorganic composite obtained by modifying an aluminum compound with an organic silane, an aluminum compound composite adsorbing a polymer, a composite coated with an organic compound, and the like. When using these composites, the content of the organic compound is not particularly limited, but is preferably 60% by mass or less, and more preferably 30% by mass or less.
　アルミニウム源の比表面積も特に限定されるものではない。モリブデン化合物が効果的に作用するため、比表面積が大きい方が好ましいが、焼成条件やモリブデン化合物の使用量を調整する事で、いずれの比表面積のものでも原料として使用することができる。 The specific surface area of the aluminum source is also not particularly limited. Since the molybdenum compound acts effectively, it is preferable that the specific surface area is large, but by adjusting the firing conditions and the amount of the molybdenum compound used, any specific surface area can be used as a raw material.
　上述したフラックス法において、アルミニウム化合物を形成するために、形状制御剤を用いることができる。形状制御剤はモリブデン化合物の存在下で、アルミニウム源の焼成によるアルミナの板状結晶成長に重要な役割を果たす。 In the above-mentioned flux method, a shape control agent can be used to form an aluminum compound. The shape control agent plays an important role in the plate crystal growth of alumina by firing an aluminum source in the presence of a molybdenum compound.
　形状制御剤の存在状態は、特に制限されず、例えば、形状制御剤とアルミニウム化合物と物理混合物、形状制御剤がアルミニウム源の表面又は内部に、均一又は局在に存在した複合体等が好適に用いることができる。 The state of existence of the shape control agent is not particularly limited, and for example, a shape control agent, an aluminum compound and a physical mixture, a complex in which the shape control agent is present uniformly or locally on the surface or inside of the aluminum source, and the like are preferable. Can be used.
　また、形状制御剤をアルミニウム化合物に添加してもよいが、アルミニウム化合物中に不純物として含んでもよい。 The shape control agent may be added to the aluminum compound, but may be included as an impurity in the aluminum compound.
　形状制御剤は板状結晶成長に重要な役割を果たす。一般的に行なわれる酸化モリブデンフラックス法では酸化モリブデンがアルミナのα結晶の（１１３）面に選択的に吸着し、結晶成分は（１１３）面に供給されにくくなり、(００１)面、又は、（００６）面の出現を完全に抑制できるとするものであることから、六角両錘型をベースとした多面体粒子を形成する。上述したフラックス法においては、形状制御剤を用いて、フラックス剤である酸化モリブデンが（１１３）面に選択的な結晶成分の吸着を抑制することで、（００１）面の発達した熱力学的に最も安定的な稠密六方格子の結晶構造を有する板状形状を形成することができる。モリブデン化合物をフラックス剤として用いることで、α結晶化率が高い、モリブデンを含む板状アルミナ粒子をより容易に形成できる。 Shape control agent plays an important role in plate crystal growth. In the molybdenum oxide flux method that is generally performed, molybdenum oxide is selectively adsorbed on the (113) plane of α crystals of alumina, and the crystal component is less likely to be supplied to the (113) plane, and the (001) plane or ( Since the appearance of the (006) plane can be completely suppressed, polyhedral particles based on a hexagonal bipyramid are formed. In the above-mentioned flux method, by using a shape control agent, molybdenum oxide, which is a flux agent, suppresses the selective adsorption of crystalline components on the (113) plane, so that the (001) plane is thermodynamically developed. It is possible to form a plate-like shape having a crystal structure of the most stable dense hexagonal lattice. By using a molybdenum compound as a flux agent, it is possible to more easily form tabular alumina particles containing molybdenum and having a high α crystallization rate.
　形状制御剤の種類については、シリコン又はケイ素元素を含むケイ素化合物、ゲルマニウム又はゲルマニウム元素を含むゲルマニウム化合物を用いることができる。より安価で生産性に優れる板状アルミナ粒子を製造可能な点からも、シリコン又はケイ素元素を含むケイ素化合物を用いることが好ましい。形状制御剤として、シリコン又はケイ素化合物を用いた上記フラックス法により、アスペクト比の高いアルミニウム化合物を容易に製造することができる。 Regarding the type of shape control agent, silicon or a silicon compound containing a silicon element, germanium or a germanium compound containing a germanium element can be used. It is preferable to use silicon or a silicon compound containing a silicon element from the viewpoint that it is possible to produce plate-like alumina particles that are less expensive and have excellent productivity. An aluminum compound having a high aspect ratio can be easily produced by the flux method using silicon or a silicon compound as the shape control agent.
　シリコン又はケイ素元素を含むケイ素化合物としては、特に制限されず、公知のものが使用されうる。シリコン又はケイ素元素を含むケイ素化合物としては、人工合成シリコン化合物であってもよく、天然シリコン化合物であってもよい。人工合成シリコン化合物としては、例えば、金属シリコン、有機シラン、シリコン樹脂、シリカ微粒子、シリカゲル、メソポーラスシリカ、ＳｉＣ、ムライト等が挙げられる。天然シリコン化合物としては、例えば、バイオシリカ等が挙げられる。中でも、アルミニウム化合物との複合、混合がより均一的に形成できる観点から、有機シラン、シリコン樹脂又はシリカ微粒子を用いることが好ましい。なお、シリコン又はケイ素元素を含むケイ素化合物は、単独で用いてもよく、２種以上を組み合わせて用いてもよい。 The silicon compound containing silicon or silicon element is not particularly limited, and known compounds can be used. The silicon compound containing silicon or a silicon element may be an artificial synthetic silicon compound or a natural silicon compound. Examples of the artificially synthesized silicon compound include metal silicon, organic silane, silicon resin, silica fine particles, silica gel, mesoporous silica, SiC, and mullite. Examples of natural silicon compounds include biosilica and the like. Above all, it is preferable to use organic silane, silicon resin, or silica fine particles from the viewpoint that the compounding and mixing with the aluminum compound can be formed more uniformly. The silicon compounds containing silicon or silicon element may be used alone or in combination of two or more kinds.
　シリコン又はケイ素元素を含むケイ素化合物の形状は、特に制限されず、例えば、球状、無定形、アスペクトのある構造体、シート等を好適に用いることができる。アスペクトのある構造体としては、例えば、ワイヤ、ファイバー、リボン、チューブ等の形状のものであっても好適に用いることができる。 The shape of silicon or a silicon compound containing a silicon element is not particularly limited, and for example, a spherical shape, an amorphous shape, a structure having an aspect, a sheet, or the like can be preferably used. As the structure having an aspect, for example, a wire, a fiber, a ribbon, a tube, or the like can be preferably used.
　アルミニウム化合物１００質量％に対するケイ素の含有量は、二酸化ケイ素換算で、１０質量％以下が好ましく、０．００１質量％以上５質量％以下がより好ましく、０．０１質量％以上４質量％以下がさらに好ましく、０．６質量％以上２．５質量％以下が特に好ましい。上記ケイ素の含有量はＸＲＦ分析により求めることができる。 The content of silicon with respect to 100 mass% of the aluminum compound is preferably 10 mass% or less, more preferably 0.001 mass% or more and 5 mass% or less, further 0.01 mass% or more and 4 mass% or less in terms of silicon dioxide. It is preferably 0.6% by mass or more and 2.5% by mass or less. The silicon content can be determined by XRF analysis.
・モリブデン化合物
　モリブデン化合物としては、特に制限されないが、金属モリブデン、酸化モリブデン、硫化モリブデン、モリブデン酸ナトリウム、モリブデン酸カリウム、モリブデン酸カルシウム、モリブデン酸アンモニウム、Ｈ３ＰＭｏ１２Ｏ４０、Ｈ３ＳｉＭｏ１２Ｏ４０等が挙げられる。この際、前記モリブデン化合物は、異性体を含む。例えば、酸化モリブデンは、二酸化モリブデン（ＩＶ）（ＭｏＯ２）であってもよく、三酸化モリブデン（ＶＩ）（ＭｏＯ３）であってもよい。なお、上述のモリブデン化合物は、単独で用いても、２種以上を組み合わせて用いてもよい。これらのうち、三酸化モリブデン、二酸化モリブデン又はモリブデン酸アンモニウムであることが好ましく、三酸化モリブデンであることがより好ましい。 The molybdenum compound molybdenum compound is not particularly limited, metallic molybdenum, molybdenum oxide, molybdenum sulfide, sodium molybdate, potassium molybdate, calcium molybdate, ammonium molybdate, H 3 PMo 12 O 40, H 3 SiMo 12 O 40 etc. are mentioned. At this time, the molybdenum compound includes isomers. For example, molybdenum oxide may be molybdenum (IV) dioxide (MoO 2 ) or molybdenum trioxide (VI) (MoO 3 ). The above molybdenum compounds may be used alone or in combination of two or more. Of these, molybdenum trioxide, molybdenum dioxide or ammonium molybdate is preferable, and molybdenum trioxide is more preferable.
　アルミニウム化合物のアルミニウム元素に対するモリブデン化合物のモリブデン元素のモル比（モリブデン元素／アルミニウム元素）は、０．０１以上３．０以下であることが好ましく、０．０３以上１．０以下であることがより好ましい。前記モル比が上記下限値以上であると、モリブデンを含むアルミニウム化合物の結晶成長がより好適に進行し得る。一方、前記モル比が上記上限値以下であると、モリブデンを含むアルミニウム化合物の調製が工業的により効率よくできる。 The molar ratio of the molybdenum element of the molybdenum compound to the aluminum element of the aluminum compound (molybdenum element/aluminum element) is preferably 0.01 or more and 3.0 or less, and more preferably 0.03 or more and 1.0 or less. preferable. When the molar ratio is at least the above lower limit, crystal growth of the aluminum compound containing molybdenum can proceed more favorably. On the other hand, when the molar ratio is not more than the above upper limit, the aluminum compound containing molybdenum can be prepared industrially more efficiently.
－フラックス蒸発工程－
　アルミニウム源及びモリブデン化合物を含む混合物を焼成することで、中間化合物であるモリブデン酸アルミニウムを経由し、前記モリブデン酸アルミニウムが分解し、モリブデン化合物が蒸発することで、モリブデンを含むアルミニウム化合物が生成する。この際、前記モリブデン化合物の蒸発がモリブデンを含むアルミニウム化合物の結晶成長の駆動力となる。 -Flux evaporation process-
By firing a mixture containing an aluminum source and a molybdenum compound, the aluminum molybdate is decomposed via the intermediate compound aluminum molybdate, and the molybdenum compound is evaporated, whereby an aluminum compound containing molybdenum is produced. At this time, the evaporation of the molybdenum compound serves as a driving force for crystal growth of the aluminum compound containing molybdenum.
　焼成温度は特に制限されないが、７００℃以上２０００℃以下であることが好ましく、９００℃以上１６００℃以下であることがより好ましく、９５０℃以上１５００℃以下であることがさらに好ましく、１０００℃以上１４００℃以下であることが特に好ましい。焼成温度が上記下限値以上であると、より好適にフラックス反応が進行する。一方、焼成温度が上記上限値以下であると、焼成炉への負担や燃料コストがより低減され得る。 The firing temperature is not particularly limited, but is preferably 700° C. or higher and 2000° C. or lower, more preferably 900° C. or higher and 1600° C. or lower, further preferably 950° C. or higher and 1500° C. or lower, and 1000° C. or higher 1400 or higher. It is particularly preferable that the temperature is not higher than °C. If the firing temperature is at least the above lower limit, the flux reaction will proceed more suitably. On the other hand, when the firing temperature is at most the above upper limit, the burden on the firing furnace and the fuel cost can be further reduced.
　焼成時におけるアルミニウム源及びモリブデン化合物の状態は、特に限定されず、モリブデン化合物及びアルミニウム源が同一の空間に存在すればよい。例えば、両者が混合されていない状態であっても、フラックス反応は進行しうる。両者を混合する場合には、粉体を混ぜ合わせる簡便な混合、粉砕機等を用いた機械的な混合、乳鉢等を用いた混合等を行うことができ、この際、得られる混合物は乾式状態、湿式状態のいずれであってもよい。 The state of the aluminum source and the molybdenum compound during firing is not particularly limited as long as the molybdenum compound and the aluminum source exist in the same space. For example, the flux reaction can proceed even when the two are not mixed. When both are mixed, simple mixing of powders, mechanical mixing using a crusher, mixing using a mortar, etc. can be performed, and the resulting mixture is in a dry state. It may be in a wet state.
　焼成の時間についても特に制限されないが、５分以上３０時間以下であることが好ましく、モリブデンを含むアルミニウム化合物の形成を効率的に行う観点から、１０分以上１５時間以下であることがより好ましい。 The firing time is also not particularly limited, but is preferably 5 minutes or more and 30 hours or less, and more preferably 10 minutes or more and 15 hours or less from the viewpoint of efficiently forming an aluminum compound containing molybdenum.
　焼成の雰囲気についても特に限定されないが、例えば、空気や酸素のような含酸素雰囲気、窒素やアルゴンのような不活性雰囲気であることが好ましく、実施者の安全性や炉の耐久性観点から腐食性を有さない含酸素雰囲気、窒素雰囲気であることがより好ましく、コストの観点から、空気雰囲気であることがさらに好ましい。 The firing atmosphere is also not particularly limited, but for example, an oxygen-containing atmosphere such as air or oxygen, or an inert atmosphere such as nitrogen or argon is preferable, and corrosion is performed from the viewpoint of the safety of the practitioner and the durability of the furnace. It is more preferable to use an oxygen-containing atmosphere having no property and a nitrogen atmosphere, and it is more preferable to use an air atmosphere from the viewpoint of cost.
　焼成装置についても特に制限されず、通常、いわゆる焼成炉を用いる。当該焼成炉は、昇華したモリブデン化合物と反応しない材質で構成されていることが好ましく、モリブデン化合物を効率的に利用可能な密閉性の高い焼成炉であることがより好ましい。 The firing device is not particularly limited, and a so-called firing furnace is usually used. The firing furnace is preferably made of a material that does not react with the sublimated molybdenum compound, and more preferably a highly tight firing furnace that can efficiently use the molybdenum compound.
－冷却工程－
　冷却工程は、焼成工程において結晶成長したアルミニウム化合物を冷却する工程である。 -Cooling process-
The cooling step is a step of cooling the aluminum compound crystal-grown in the firing step.
　冷却速度は、特に制限されないが、１℃／時間以上１０００℃／時間以下であることが好ましく、５℃／時間以上５００℃／時間以下であることがより好ましく、５０℃／時間以上１００℃／時間以下であることがさらに好ましい。冷却速度が上記下限値以上であると、製造時間がより短縮され得る。一方、冷却速度が上記上限値以下であると、焼成容器がヒートショックで割れることがより少なく、より長く使用できることから好ましい。 The cooling rate is not particularly limited, but is preferably 1° C./hour or more and 1000° C./hour or less, more preferably 5° C./hour or more and 500° C./hour or less, and 50° C./hour or more 100° C./hour. More preferably, it is less than or equal to time. When the cooling rate is equal to or higher than the above lower limit value, the manufacturing time can be further shortened. On the other hand, when the cooling rate is less than or equal to the above upper limit, the firing container is less likely to be cracked by heat shock and can be used for a longer time, which is preferable.
　冷却方法は特に制限されず、自然放冷であっても、冷却装置を使用してもよい。 The cooling method is not particularly limited, and natural cooling or a cooling device may be used.
－モリブデンを含むアルミニウム化合物－
　フラックス法により得られるアルミニウム化合物は、モリブデンを含むため、通常、着色されている。着色された色彩は、含有されるモリブデンの量によっても異なるが、通常、薄い青色から黒色に近い濃青色であり、モリブデン含有量に比例して色彩が濃色になる傾向がある。なお、モリブデンを含むアルミニウム化合物の構成によっては、他の色彩に着色されている場合もある。例えば、モリブデンを含む化合物がクロムを含む場合には赤色に、ニッケルを含む場合には黄色になりうる。 -Aluminum compound containing molybdenum-
Since the aluminum compound obtained by the flux method contains molybdenum, it is usually colored. Although the colored color varies depending on the amount of molybdenum contained, it is usually a light blue to a dark blue color close to black, and the color tends to become dark in proportion to the molybdenum content. The aluminum compound containing molybdenum may be colored in another color. For example, the compound containing molybdenum may be red when it contains chromium, and may be yellow when it contains nickel.
　モリブデンを含むアルミニウム化合物のモリブデンの含有量は、特に制限されないが、三酸化モリブデン換算で、０．１質量％以上１質量％以下であることが好ましく、０．２質量％以上０．９質量％以下であることがより好ましく、０．３質量％以上０．９質量％以下であることがさらに好ましく、０．５質量％以上０．８８質量％以下がよりさらに好ましく、０．７質量％以上０．８７質量％以下が特に好ましく、０．８３質量％以上０．８６質量％以下が最も好ましい。モリブデンの含有量が上記下限値以上であると、スピネルの結晶成長がより効率よく進行できる。一方、モリブデンの含有量が上記上限値以下であると、アルミニウム化合物の結晶品質が向上しうることから好ましい。なお、本明細書において、アルミニウム化合物中のモリブデンの含有量は、上記板状スピネル粒子中のモリブデンの含有量に記載の方法と同様の方法を用いて測定することができる。 The content of molybdenum in the aluminum compound containing molybdenum is not particularly limited, but is preferably 0.1% by mass or more and 1% by mass or less and 0.2% by mass or more and 0.9% by mass in terms of molybdenum trioxide. It is more preferably at most 0.3% by mass and at most 0.9% by mass, even more preferably at least 0.5% by mass and at most 0.88% by mass, and at least 0.7% by mass. 0.87 mass% or less is particularly preferable, and 0.83 mass% or more and 0.86 mass% or less is most preferable. When the content of molybdenum is not less than the above lower limit, spinel crystal growth can proceed more efficiently. On the other hand, when the content of molybdenum is not more than the above upper limit value, the crystal quality of the aluminum compound can be improved, which is preferable. In the present specification, the content of molybdenum in the aluminum compound can be measured by the same method as the method described in the content of molybdenum in the plate-like spinel particles.
　モリブデンを含むアルミニウム化合物は、モリブデンがフラックス剤として働き、（００１）面以外の結晶面を主結晶面とした高α結晶化率であることが好ましく、α結晶化率が９０％以上であることがより好ましい。 The aluminum compound containing molybdenum preferably has a high α crystallization rate with molybdenum serving as a flux agent and having a crystal plane other than the (001) plane as a main crystal plane, and the α crystallization rate is 90% or more. Is more preferable.
（徐冷法）
　また、一実施形態において、フラックス法は、アルミニウム源及びモリブデン化合物を含む混合物を焼成する工程と、得られる焼成物を冷却して結晶成長させる徐冷工程と、を含む。 (Slow cooling method)
Further, in one embodiment, the flux method includes a step of firing a mixture containing an aluminum source and a molybdenum compound, and a slow cooling step of cooling the obtained fired material to grow crystals.
［モリブデン］
　モリブデンは、固相反応において、界面における核形成の促進、マグネシウム原子及びアルミニウム原子のうち少なくともいずれかの原子の固相拡散の促進等の機能を有する。 [molybdenum]
Molybdenum has a function of promoting nucleation at the interface in the solid phase reaction, promoting solid phase diffusion of at least one atom of magnesium atom and aluminum atom, and the like.
　モリブデンは、モリブデン金属及びモリブデンを含む化合物中のモリブデンが用いられうる。モリブデンを含む化合物の具体例としては、上述したモリブデン化合物、モリブデンを含むアルミニウム化合物が挙げられる。なお、モリブデンを含むアルミニウム化合物は、モリブデンを含む化合物、かつ、アルミニウム化合物として使用されうる。上述のモリブデンは、単独で用いても、２種以上を組み合わせて用いてもよい。 As molybdenum, molybdenum in a compound containing molybdenum metal and molybdenum may be used. Specific examples of the compound containing molybdenum include the above-mentioned molybdenum compound and the aluminum compound containing molybdenum. The aluminum compound containing molybdenum can be used as a compound containing molybdenum and an aluminum compound. The above molybdenum may be used alone or in combination of two or more kinds.
　モリブデンの使用量として、アルミニウム化合物のアルミニウム元素に対するモリブデン元素のモル比（モリブデン元素／アルミニウム元素）は、０．００００１以上０．０５以下であることが好ましく、０．０００１以上０．０３以下であることがより好ましい。前記モル比が上記範囲内であると、マグネシウム化合物とアルミニウム化合物との固溶化及びスピネル晶出がより好適に進行し得る。 As the amount of molybdenum used, the molar ratio of molybdenum element to aluminum element of the aluminum compound (molybdenum element/aluminum element) is preferably 0.00001 or more and 0.05 or less, and 0.0001 or more and 0.03 or less. Is more preferable. When the molar ratio is within the above range, solid solution of the magnesium compound and the aluminum compound and spinel crystallization can proceed more favorably.
＜焼成工程＞
　焼成工程は、マグネシウム化合物及びアルミニウム化合物を、モリブデン存在下で、
固溶化及び晶出により、上記板状スピネル粒子に結晶成長させる工程である。 <Firing process>
In the firing step, a magnesium compound and an aluminum compound are added in the presence of molybdenum,
It is a step of crystallizing the plate-like spinel particles by solid solution and crystallization.
　前記固溶化及び晶出は、通常、いわゆる固相法により行われる。固相法における固溶化及び晶出のメカニズムとしては、以下のとおりであると推測される。すなわち、マグネシウム化合物及びアルミニウム化合物が接触する環境下において加熱を行うと、マグネシウム化合物及びアルミニウム化合物が界面（固相界面）において核を形成することで、固相間の結合が強化される。そして、前記形成された核を担体として、固相反応が進行しうる。この際、前記固相反応は、マグネシウム化合物及びアルミニウム化合物の二元系状態図が共晶型をとること、これによりマグネシウム化合物及びアルミニウム化合物が界面における反応できる温度はマグネシウム化合物又はアルミニウム化合物が単独で溶融する温度よりも低いことが利用されうる。具体的には、マグネシウム化合物及びアルミニウム化合物が界面において反応して核を形成し、マグネシウム原子及びアルミニウム原子のうち少なくともいずれかの原子が、前記核を介して固相拡散し、アルミニウム化合物及びマグネシウム原子のうち少なくともいずれかの原子と反応する。これにより、緻密な結晶体、すなわちスピネル粒子を得ることができる。この際、前記固相拡散において、マグネシウム原子のアルミニウム化合物への拡散速度は、アルミニウム原子のマグネシウム化合物への拡散速度よりも相対的に高いため、アルミニウム化合物の形状が反映されたスピネル粒子が得られる傾向がある。このため、アルミニウム化合物の形状や平均粒子径を適宜変更することで、スピネル粒子の形状及び平均粒子径を制御することが可能となり得る。実施形態に係る製造方法では、アルミニウム化合物としてモリブデンを含む板状アルミナ粒子を用いることで、板状スピネル粒子をより容易に製造することができる。 The solid solution and crystallization are usually carried out by the so-called solid phase method. The mechanism of solid solution and crystallization in the solid phase method is presumed to be as follows. That is, when heating is performed in an environment in which the magnesium compound and the aluminum compound are in contact with each other, the magnesium compound and the aluminum compound form nuclei at the interface (solid phase interface), so that the bond between the solid phases is strengthened. Then, the solid phase reaction can proceed using the formed nucleus as a carrier. At this time, the solid phase reaction is that the binary phase diagram of the magnesium compound and the aluminum compound has a eutectic type, whereby the temperature at which the magnesium compound and the aluminum compound can react at the interface is the magnesium compound or the aluminum compound alone. Lower than melting temperature can be utilized. Specifically, the magnesium compound and the aluminum compound react at the interface to form a nucleus, and at least one atom of the magnesium atom and the aluminum atom is solid-phase diffused through the nucleus, and the aluminum compound and the magnesium atom. Reacts with at least one of the atoms. Thereby, a dense crystal body, that is, spinel particles can be obtained. At this time, in the solid phase diffusion, the diffusion rate of magnesium atoms into the aluminum compound is relatively higher than the diffusion rate of aluminum atoms into the magnesium compound, so that spinel particles in which the shape of the aluminum compound is reflected are obtained. Tend. Therefore, it may be possible to control the shape and the average particle diameter of the spinel particles by appropriately changing the shape and the average particle diameter of the aluminum compound. In the manufacturing method according to the embodiment, the plate-shaped spinel particles can be manufactured more easily by using the plate-shaped alumina particles containing molybdenum as the aluminum compound.
　ここで、上述の固相反応は、モリブデン存在下で行われる。モリブデンの作用は必ずしも明らかではないが、例えば、界面における核形成の促進、マグネシウム原子及びアルミニウム原子のうち少なくともいずれかの原子の固相拡散の促進等により、固相反応がより好適に進行するものと考えられる。また、上述のフラックス法において説明したとおり、反応の過程として、まずモリブデンとアルミニウム化合物とが反応して、中間体であるモリブデン酸アルミニウムが形成された後、当該モリブデン酸アルミニウムとマグネシウム化合物とが反応するものを含むと推察される。金属成分を複数有するスピネル粒子では、焼成過程において、欠陥構造等が生じやすいため、結晶構造を精密に制御することが困難であるが、モリブデンを用いることにより、スピネル結晶の結晶構造を制御することができる。これにより、（３１１）面の結晶子径は大きくなり、熱伝導性に優れる板状スピネル粒子が得られうる。なお、固相反応は、モリブデン存在下で行われるため、得られる板状スピネル粒子には、モリブデンが含まれうる。 Here, the above solid-phase reaction is performed in the presence of molybdenum. Although the action of molybdenum is not always clear, for example, solid-phase reaction proceeds more favorably by promoting nucleation at the interface, promoting solid-phase diffusion of at least one of magnesium and aluminum atoms, and the like. it is conceivable that. Further, as described in the above-described flux method, as a process of the reaction, first, molybdenum and an aluminum compound are reacted to form an aluminum intermediate molybdate, and then the aluminum molybdate and the magnesium compound are reacted. It is presumed to include things that do. With spinel particles having a plurality of metal components, it is difficult to precisely control the crystal structure because a defect structure or the like is likely to occur during the firing process. However, by using molybdenum, it is possible to control the crystal structure of the spinel crystal. You can Thereby, the crystallite diameter of the (311) plane becomes large, and plate-like spinel particles having excellent thermal conductivity can be obtained. Since the solid phase reaction is performed in the presence of molybdenum, the obtained plate-like spinel particles may contain molybdenum.
　なお、スピネル粒子の（３１１）面の結晶子径等の結晶制御は、モリブデンの使用量、マグネシウム化合物の種類、焼成温度、焼成時間、マグネシウム化合物とアルミニウム化合物との混合状態を変更することにより行うことができる。この理由は、モリブデンの量、マグネシウム化合物の種類、焼成温度、焼成時間、マグネシウム化合物とアルミニウム化合物との混合状態は、固相反応において、マグネシウム化合物及びアルミニウム化合物に固溶化及び晶出の速度等に関連するためであると考えられる。高反応性マグネシウム化合物の使用はマグネシウム化合物の固溶化及び晶出の速度を、モリブデンの使用量の増加、高温焼成、及び長時間焼成はマグネシウム原子及びアルミニウム原子のうち少なくともいずれかの原子の固溶化及び晶出の速度を、それぞれ早くすることができ、例えば、（３１１）面の結晶子径を大きくすることができる。 The crystallite size of the (311) plane of the spinel particles is controlled by changing the amount of molybdenum used, the type of magnesium compound, the firing temperature, the firing time, and the mixed state of the magnesium compound and the aluminum compound. be able to. The reason is that the amount of molybdenum, the type of magnesium compound, the firing temperature, the firing time, and the mixed state of the magnesium compound and the aluminum compound depend on the rate of solid solution and crystallization in the magnesium compound and the aluminum compound in the solid phase reaction. It is considered to be related. The use of a highly reactive magnesium compound increases the rate of solid solution and crystallization of the magnesium compound, and the increase in the amount of molybdenum used, high temperature calcination, and long time calcination solidify at least one of magnesium and aluminum atoms. And the rate of crystallization can be respectively increased, and for example, the crystallite diameter of the (311) plane can be increased.
　焼成温度は、特別な限定はないが、１３００℃未満が好ましく、８００℃以上１３００℃未満がより好ましく、９００℃以上１２００℃以下がさらに好ましい。焼成温度が上記上限値以下であることで、より短時間でより効率的に板状スピネル粒子を製造することができる。一方で、焼成温度が上記上限値以下であることで、スピネル粒子の形状及び分散性をより容易に制御することができる。 The firing temperature is not particularly limited, but is preferably lower than 1300°C, more preferably 800°C or higher and lower than 1300°C, and further preferably 900°C or higher and 1200°C or lower. When the firing temperature is at most the above upper limit, the plate-like spinel particles can be produced more efficiently in a shorter time. On the other hand, when the firing temperature is not more than the above upper limit, the shape and dispersibility of spinel particles can be controlled more easily.
　焼成時間は、特に制限されないが、０．１時間以上１０００時間以下であることが好ましく、３時間以上１００時間以下であることがより好ましい。焼成時間が上記下限値以上であると、（３１１）面の結晶子径のより大きな板状スピネル粒子を得ることができる。一方、焼成時間が上記上限値以下であると、製造コストがより低くなり得る。 The firing time is not particularly limited, but is preferably 0.1 hour or more and 1000 hours or less, and more preferably 3 hours or more and 100 hours or less. When the firing time is at least the above lower limit, plate-like spinel particles having a larger crystallite size on the (311) plane can be obtained. On the other hand, when the firing time is not more than the above upper limit value, the manufacturing cost may be lower.
　なお、焼成においては、マグネシウム化合物とアルミニウム化合物との固溶化及び晶出を促進するため、及び、形状を制御するために、形状制御剤を使用することも可能である。当該形状制御剤としては、例えば、ナトリウム化合物、カリウム化合物等が挙げられる。形状制御剤を添加することで、モリブデンが効率よく拡散され結晶形成の均質化へ寄与し、形状や粒子表面がより均一で平滑性の高い板状スピネル粒子を得る事ができる。 In the firing, it is also possible to use a shape control agent in order to promote the solid solution and crystallization of the magnesium compound and the aluminum compound and to control the shape. Examples of the shape control agent include sodium compounds and potassium compounds. By adding the shape control agent, molybdenum is efficiently diffused to contribute to homogenization of crystal formation, and plate-like spinel particles having a more uniform shape and particle surface and high smoothness can be obtained.
　ナトリウム化合物としては、特に制限されないが、ナトリウム、塩化ナトリウム、亜塩素酸ナトリウム、塩素酸ナトリウム、硫酸ナトリウム、硫酸水素ナトリウム、亜硫酸ナトリウム、亜硫酸水素ナトリウム、硝酸ナトリウム、炭酸ナトリウム、炭酸水素ナトリウム、酢酸ナトリウム、酸化ナトリウム、臭化ナトリウム、臭素酸ナトリウム、水酸化ナトリウム、珪酸ナトリウム、燐酸ナトリウム、燐酸水素ナトリウム、硫化ナトリウム、硫化水素ナトリウム、モリブデン酸ナトリウム、タングステン酸ナトリウム等が挙げられる。この際、前記ナトリウム化合物は、モリブデン化合物の場合と同様に、異性体を含む。中でも、炭酸ナトリウム、炭酸水素ナトリウム、酸化ナトリウム、水酸化ナトリウム、塩化ナトリウム、硫酸ナトリウム又はモリブデン酸ナトリウムを用いることが好ましく、炭酸ナトリウム、炭酸水素ナトリウム、塩化ナトリウム、硫酸ナトリウム又はモリブデン酸ナトリウムを用いることがより好ましい。なお、上述のナトリウム化合物は、単独で用いてもよく、２種以上を組み合わせて用いてもよい。また、モリブデン酸ナトリウムは、モリブデンを含むため、上述のモリブデン化合物としての機能も有しうる。 The sodium compound is not particularly limited and includes sodium, sodium chloride, sodium chlorite, sodium chlorate, sodium sulfate, sodium hydrogen sulfate, sodium sulfite, sodium hydrogen sulfite, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, sodium acetate. , Sodium oxide, sodium bromide, sodium bromate, sodium hydroxide, sodium silicate, sodium phosphate, sodium hydrogen phosphate, sodium sulfide, sodium hydrogen sulfide, sodium molybdate, sodium tungstate and the like. At this time, the sodium compound includes isomers as in the case of the molybdenum compound. Among them, sodium carbonate, sodium hydrogen carbonate, sodium oxide, sodium hydroxide, sodium chloride, sodium sulfate or sodium molybdate is preferably used, and sodium carbonate, sodium hydrogen carbonate, sodium chloride, sodium sulfate or sodium molybdate is used. Is more preferable. The sodium compounds described above may be used alone or in combination of two or more. Further, since sodium molybdate contains molybdenum, it can also have a function as the above-mentioned molybdenum compound.
　カリウム化合物としては、特に制限されないが、カリウム、塩化カリウム、亜塩素酸カリウム、塩素酸カリウム、硫酸カリウム、硫酸水素カリウム、亜硫酸カリウム、亜硫酸水素カリウム、硝酸カリウム、炭酸カリウム、炭酸水素カリウム、酢酸カリウム、酸化カリウム、臭化カリウム、臭素酸カリウム、水酸化カリウム、珪酸カリウム、燐酸カリウム、燐酸水素カリウム、硫化カリウム、硫化水素カリウム、モリブデン酸カリウム、タングステン酸カリウム等が挙げられる。この際、前記カリウム化合物は、モリブデン化合物の場合と同様に、異性体を含む。中でも、炭酸カリウム、炭酸水素カリウム、酸化カリウム、水酸化カリウム、塩化カリウム、硫酸カリウム又はモリブデン酸カリウムを用いることが好ましく、炭酸カリウム、炭酸水素カリウム、塩化カリウム、硫酸カリウム又はモリブデン酸カリウムを用いることがより好ましい。なお、上述のカリウム化合物は、単独で用いてもよく、２種以上を組み合わせて用いてもよい。また、モリブデン酸カリウムは、モリブデンを含むため、上述のモリブデン化合物としての機能も有しうる。 The potassium compound is not particularly limited, potassium, potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium acetate, Examples thereof include potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, potassium tungstate, and the like. At this time, the potassium compound includes isomers, as in the case of the molybdenum compound. Among them, potassium carbonate, potassium hydrogen carbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate or potassium molybdate is preferably used, and potassium carbonate, potassium hydrogen carbonate, potassium chloride, potassium sulfate or potassium molybdate is used. Is more preferable. The above potassium compounds may be used alone or in combination of two or more. Further, since potassium molybdate contains molybdenum, it can also have a function as the above-mentioned molybdenum compound.
　形状制御剤の添加量としては、原料１００質量％に対して、酸化物換算で、２０質量％以上９０質量％以下であることが好ましく、３０質量％以上８０質量％以下であることがより好ましく、４０質量％以上７０質量％以下であることがさらに好ましく、５０質量％以上６８質量％以下がよりさらに好ましく、５５質量％以上６７質量％以下が特に好ましく、６１質量％以上６６質量％以下が最も好ましい。形状制御剤の添加量が上記範囲内であることで、表面の平滑性により優れた板状スピネル粒子を得ることができる。また、アスペクト比をより大きくすることができ、機械強度により優れる傾向がある。
　これら添加剤は、上記混合工程において焼成前に混合しておくことが好ましい。 The amount of the shape control agent added is preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 80% by mass or less, in terms of oxide, based on 100% by mass of the raw material. , 40% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 68% by mass or less, particularly preferably 55% by mass or more and 67% by mass or less, and 61% by mass or more and 66% by mass or less. Most preferred. When the amount of the shape control agent added is within the above range, it is possible to obtain plate-like spinel particles having more excellent surface smoothness. Further, the aspect ratio can be increased, and the mechanical strength tends to be superior.
These additives are preferably mixed in the above mixing step before firing.
　焼成雰囲気は、空気雰囲気であってもよく、窒素ガスやアルゴンガス等の不活性ガス雰囲気であってもよく、酸素雰囲気であってもよく、アンモニアガス雰囲気であってもよく、二酸化炭素雰囲気であってもよい。この際、製造コストの観点からは空気雰囲気であることが好ましい。 The firing atmosphere may be an air atmosphere, an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen atmosphere, an ammonia gas atmosphere, or a carbon dioxide atmosphere. It may be. At this time, an air atmosphere is preferable from the viewpoint of manufacturing cost.
　焼成時の圧力についても特に制限されず、常圧下であってもよく、加圧下であってもよく、減圧下であってもよいが、焼成時に生成する酸化モリブデン蒸気を効率的に焼成炉から排出できる観点から減圧下で行うことが好ましい。 The pressure during firing is also not particularly limited, and may be under normal pressure, may be under pressure, or may be under reduced pressure, but molybdenum oxide vapor generated during firing can be efficiently generated from the firing furnace. From the viewpoint of being able to discharge, it is preferable to carry out under reduced pressure.
　加熱手段としては、特に制限されない、焼成炉を用いることが好ましい。この際使用されうる焼成炉としては、トンネル炉、ローラーハース炉、ロータリーキルン、マッフル炉等が挙げられる。
　焼成炉は酸化モリブデン蒸気と反応しない材質で構成されていることが好ましく、密閉性の高い焼成炉を用いることがより好ましい。 The heating means is preferably a firing furnace, which is not particularly limited. Examples of firing furnaces that can be used at this time include tunnel furnaces, roller hearth furnaces, rotary kilns, and muffle furnaces.
It is preferable that the firing furnace is made of a material that does not react with molybdenum oxide vapor, and it is more preferable to use a firing furnace having high airtightness.
＜冷却工程＞
　本発明の製造方法は、冷却工程を含んでいてもよい。当該冷却工程は、焼成工程において結晶成長したスピネル粒子を冷却する工程である。 <Cooling process>
The manufacturing method of the present invention may include a cooling step. The cooling step is a step of cooling the spinel particles having crystal grown in the firing step.
　冷却速度は、特に制限されないが、１℃／時間以上１０００℃／時間以下であることが好ましく、５℃／時間以上５００℃／時間以下であることがより好ましく、５０℃／時間以上１００℃／時間以下であることがさらに好ましい。冷却速度が上記下限値以上であると、製造時間がより短縮され得る。一方、冷却速度が上記上限値以下であると、焼成容器がヒートショックで割れることがより少なく、より長く使用できる。 The cooling rate is not particularly limited, but is preferably 1° C./hour or more and 1000° C./hour or less, more preferably 5° C./hour or more and 500° C./hour or less, and 50° C./hour or more 100° C./hour. More preferably, it is less than or equal to time. When the cooling rate is equal to or higher than the above lower limit value, the manufacturing time can be further shortened. On the other hand, when the cooling rate is less than or equal to the above upper limit, the firing container is less likely to be cracked by heat shock and can be used for a longer time.
　冷却方法は特に制限されず、自然放冷であってもよく、冷却装置を使用してもよい。 The cooling method is not particularly limited, and natural cooling may be used, or a cooling device may be used.
［後処理工程］
　本発明の製造方法は、後処理工程を含んでいてもよい。当該後処理工程は、添加剤等を除去する工程である。後処理工程は、上述の焼成工程の後に行ってもよく、上述の冷却工程の後に行ってもよく、焼成工程及び冷却工程の後に行ってもよい。また、必要に応じて、２度以上繰り返し行ってもよい。
　後処理の方法としては、洗浄及び高温処理が挙げられる。これらは組み合わせて行うことができる。
　前記洗浄方法としては、特に制限されないが、例えば、水、アンモニア水溶液、水酸化ナトリウム水溶液、酸性水溶液等で洗浄することにより除去することができる。
　この際、使用する水、アンモニア水溶液、水酸化ナトリウム水溶液、酸性水溶液の濃度、使用量、並びに洗浄部位及び洗浄時間等を適宜変更することで、モリブデン含有量を制御することができる。
　また、高温処理の方法としては、添加剤の昇華点又は沸点以上に昇温する方法が挙げられる。 [Post-treatment process]
The manufacturing method of the present invention may include a post-treatment step. The post-treatment step is a step of removing additives and the like. The post-treatment step may be performed after the above-mentioned firing step, may be performed after the above-mentioned cooling step, or may be performed after the firing step and the cooling step. Moreover, you may repeat twice or more as needed.
Examples of the post-treatment method include washing and high temperature treatment. These can be performed in combination.
The washing method is not particularly limited, but it can be removed by washing with water, an aqueous ammonia solution, an aqueous sodium hydroxide solution, an acidic aqueous solution, or the like.
At this time, the molybdenum content can be controlled by appropriately changing the concentration, the amount of water used, the aqueous ammonia solution, the aqueous sodium hydroxide solution, the acidic aqueous solution, the washing site, the washing time, and the like.
In addition, as a method of high temperature treatment, a method of raising the temperature above the sublimation point or boiling point of the additive can be mentioned.
［粉砕工程］
　焼成物は板状スピネル粒子が凝集して、本発明に好適な粒子径の範囲を満たさない場合がある。そのため、板状スピネル粒子は、必要に応じて、本発明に好適な粒子径の範囲を満たすように粉砕してもよい。
　焼成物の粉砕の方法は特に限定されず、ボールミル、ジョークラッシャー、ジェットミル、ディスクミル、スペクトロミル、グラインダー、ミキサーミル等の従来公知の粉砕方法を適用できる。 [Crushing process]
In the calcined product, plate-like spinel particles may aggregate and may not satisfy the particle size range suitable for the present invention. Therefore, the plate-like spinel particles may be pulverized, if necessary, so as to satisfy the particle size range suitable for the present invention.
The method for pulverizing the fired product is not particularly limited, and conventionally known pulverizing methods such as a ball mill, a jaw crusher, a jet mill, a disc mill, a spectro mill, a grinder, and a mixer mill can be applied.
［分級工程］
　板状スピネル粒子は、平均粒子径を調整し、粉体の流動性を向上するため、又はマトリックスを形成するためのバインダーに配合したときの粘度上昇を抑制するために、好ましくは分級処理される。「分級処理」とは、粒子の大きさによって粒子をグループ分けする操作をいう。
　分級は湿式、乾式のいずれでも良いが、生産性の観点からは、乾式の分級が好ましい。乾式の分級には、篩による分級のほか、遠心力と流体抗力の差によって分級する風力分級等があるが、分級精度の観点からは、風力分級が好ましく、コアンダ効果を利用した気流分級機、旋回気流式分級機、強制渦遠心式分級機、半自由渦遠心式分級機等の分級機を用いて行うことができる。
　上記した粉砕工程や分級工程は、後述する有機化合物層形成工程の前後を含めて、必要な段階において行うことができる。これら粉砕や分級の有無やそれらの条件選定により、例えば、得られる板状スピネル粒子の平均粒子径を調整することができる。 [Classification process]
The plate-like spinel particles are preferably classified in order to adjust the average particle size and improve the fluidity of the powder, or to suppress an increase in viscosity when blended in a binder for forming a matrix. .. The "classifying treatment" refers to an operation of grouping particles according to the size of the particles.
The classification may be either wet or dry, but from the viewpoint of productivity, dry classification is preferred. Dry classification, in addition to classification by a sieve, there is a wind classification that classifies by the difference in centrifugal force and fluid drag force, but from the viewpoint of classification accuracy, wind classification is preferable, and an air classifier that utilizes the Coanda effect, It can be performed using a classifier such as a swirling air flow classifier, a forced vortex centrifugal classifier, a semi-free vortex centrifugal classifier, or the like.
The crushing step and the classification step described above can be performed at necessary stages, including before and after the organic compound layer forming step described later. The average particle size of the obtained plate-like spinel particles can be adjusted by the presence or absence of the pulverization or classification and the selection of the conditions.
　実施形態に係る板状スピネル粒子、或いは実施形態に係る製造方法で得る板状スピネル粒子は、凝集が少ないもの或いは凝集していないものが、本来の性質を発揮しやすく、それ自体の取扱性により優れており、また被分散媒体に分散させて用いる場合において、より分散性に優れる観点から、好ましい。板状スピネル粒子の製造方法においては、上記した粉砕工程や分級工程は行わずに、凝集が少ないもの或いは凝集していないものが得られれば、左記工程を行う必要もなく、目的の優れた性質を有する板状スピネル粒子を、生産性高く製造することができるので好ましい。 Plate-like spinel particles according to the embodiment, or plate-like spinel particles obtained by the manufacturing method according to the embodiment, those with little aggregation or non-aggregation, easily exhibit the original properties, depending on the handleability of itself. It is preferable because it is excellent, and when it is used by being dispersed in a medium to be dispersed, it is more excellent in dispersibility. In the method for producing plate-like spinel particles, without the above-mentioned pulverization step or classification step, if there is little aggregation or one that does not aggregate, it is not necessary to perform the step on the left, and the desired excellent properties are obtained. It is preferable because the plate-like spinel particles having the above can be produced with high productivity.
　以下、実施例により本発明を説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the following examples.
≪原料α－アルミナ粒子の合成≫
＜合成例１＞α－アルミナ粒子Ａ－１の合成
　水酸化アルミニウム１４５．３ｇ（日本軽金属株式会社製、平均粒子径１２μｍ）と、二酸化珪素（関東化学株式会社製、特級）１．９０ｇと、三酸化モリブデン（太陽鉱工株式会社製）５ｇとを乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１１００℃まで昇温し、１１００℃で１０時間焼成を行なった。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、９９ｇの薄青色の粉末を得た。得られた粉末を乳鉢で、１０６μｍ篩を通るまで解砕した。
　続いて、得られた前記薄青色粉末の９８ｇを０．５％アンモニア水の１５０ｍＬに分散し、分散溶液を室温（２５～３０℃）で０．５時間攪拌後、ろ過によりアンモニア水を除き、水洗浄と乾燥を行う事で、粒子表面に残存するモリブデンを除去し、９６ｇの白色の粉末を得た。得られた粉末はレーザー回折式粒度分布計により求めた平均粒子径が７．０μｍであり、また、ＳＥＭ観察により形状が多角板状であり、凝集体が極めて少なく、優れた取り扱い性を有する板状形状の粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、α－アルミナに由来する鋭いピーク散乱が現れ、α結晶構造以外のアルミナ結晶系ピークは観察されなく、緻密な結晶構造を有する板状アルミナであることを確認した。また、α化率は９０％以上であった。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．８３質量％含むものであることを確認した。さらに、密度を測定した結果３．９５ｇ／ｃｍ３であった。 <<Synthesis of raw material α-alumina particles>>
<Synthesis Example 1> Synthesis of α-alumina particles A-1 145.3 g of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., average particle diameter 12 μm) and silicon dioxide (manufactured by Kanto Chemical Co., Inc., special grade) 1.90 g, 5 g of molybdenum trioxide (Taiyo Minko Co., Ltd.) was mixed in a mortar to obtain a mixture. The obtained mixture was put into a crucible, heated to 1100° C. under a condition of 5° C./min in a ceramic electric furnace, and fired at 1100° C. for 10 hours. After that, the temperature was lowered to room temperature under the condition of 5° C./min, and the crucible was taken out to obtain 99 g of a light blue powder. The obtained powder was crushed in a mortar until it passed through a 106 μm sieve.
Subsequently, 98 g of the obtained light blue powder was dispersed in 150 mL of 0.5% aqueous ammonia, the dispersion solution was stirred at room temperature (25 to 30° C.) for 0.5 hours, and then the aqueous ammonia was removed by filtration. Molybdenum remaining on the surface of the particles was removed by washing with water and drying to obtain 96 g of white powder. The obtained powder had an average particle size of 7.0 μm as determined by a laser diffraction type particle size distribution analyzer, and had a polygonal plate shape by SEM observation, which had very few aggregates and had excellent handleability. It was confirmed that the particles were shaped like particles. Further, when XRD measurement was carried out, sharp peak scattering derived from α-alumina appeared, and no alumina crystal system peak other than α crystal structure was observed, which confirmed that the plate-like alumina had a dense crystal structure. .. Moreover, the alpha conversion rate was 90% or more. Furthermore, it was confirmed from the results of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.83 mass% of molybdenum in terms of molybdenum trioxide. Furthermore, the result of measuring the density was 3.95 g/cm 3 .
＜合成例２＞α－アルミナ粒子Ａ－２の合成
　水酸化アルミニウム（日本軽金属株式会社製、平均粒子径２μｍ）１４５．３ｇと、二酸化珪素２．８５ｇと、三酸化モリブデン（太陽鉱工株式会社製）５ｇとを乳鉢で混合した以外は、合成例１と同様の操作を行い９８ｇの薄青色の粉末を得た。得られた粉末はレーザー回折式粒度分布計により求めた平均粒子径が３．８μｍであり、また、ＳＥＭ観察により形状が多角板状であり、凝集体が極めて少なく、優れた取り扱い性を有する板状形状の粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、α－アルミナに由来する鋭いピーク散乱が現れ、α結晶構造以外のアルミナ結晶系ピークは観察されなく、緻密な結晶構造を有する板状アルミナであることを確認した。また、α化率は９０％以上であった。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．８６質量％含むものであることを確認した。さらに、密度を測定した結果３．９４ｇ／ｃｍ３であった。 <Synthesis Example 2> Synthesis of α-alumina particles A-2 145.3 g of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., average particle diameter 2 μm), 2.85 g of silicon dioxide, and molybdenum trioxide (Taiyo Mining Co., Ltd.) The same operation as in Synthesis Example 1 was carried out except that 5 g of the product) was mixed in a mortar to obtain 98 g of a pale blue powder. The obtained powder had an average particle diameter of 3.8 μm as determined by a laser diffraction type particle size distribution analyzer, and had a polygonal plate shape by SEM observation, which had very few aggregates and had excellent handleability. It was confirmed that the particles were shaped like particles. Further, when XRD measurement was carried out, sharp peak scattering derived from α-alumina appeared, and no alumina crystal system peak other than α crystal structure was observed, which confirmed that the plate-like alumina had a dense crystal structure. .. Moreover, the alpha conversion rate was 90% or more. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained molybdenum in an amount of 0.86% by mass in terms of molybdenum trioxide. Furthermore, the result of measuring the density was 3.94 g/cm 3 .
≪スピネル粒子の合成≫
＜実施例１＞スピネル粒子Ｓ－ａ１の合成
　合成例１で得たα－アルミナ粒子Ａ－１　２０ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇとを乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１０５０℃まで昇温し、１０５０℃で１０時間保持し焼成を行なった。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、２７．５ｇの白色の粉末を得た。得られた粉末を乳鉢で、１５０μｍ篩を通るまで解砕した。
　続いて、得られた前記白色粉末の２５ｇと２％硝酸の１００ｍＬを配合し、直径５ｍｍのアルミナビーズを加え、ペイントコンディショナーで２０分解砕を行った。その後、分散溶液をろ過により２％硝酸を除き、水洗浄と乾燥を行うことで、粒子表面に残存するモリブデンを除去し、２４．５ｇの白色の粉末を得た。得られた粉末はＳＥＭ観察（図１（Ａ）参照）により板状であり、凝集体が極めて少なく、優れた取り扱い性を有する粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、７２ｎｍであることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．４４質量％含むものであることを確認した。 <<Synthesis of spinel particles>>
<Example 1> Synthesis of spinel particles S-a1 20 g of α-alumina particles A-1 obtained in Synthesis Example 1 and 7.86 g of magnesium oxide (average particle diameter 3.5 μm manufactured by Kajima Chemical Co., Ltd.) were mixed in a mortar. , A mixture was obtained. The obtained mixture was put into a crucible, heated to 1050° C. under a condition of 5° C./min in a ceramic electric furnace, and kept at 1050° C. for 10 hours for firing. After that, the temperature was lowered to room temperature under the condition of 5° C./min, and the crucible was taken out to obtain 27.5 g of white powder. The obtained powder was crushed in a mortar until it passed through a 150 μm sieve.
Subsequently, 25 g of the obtained white powder and 100 mL of 2% nitric acid were blended, alumina beads having a diameter of 5 mm were added, and 20 pieces were crushed and crushed with a paint conditioner. Thereafter, the dispersion solution was filtered to remove 2% nitric acid, and washed with water and dried to remove the molybdenum remaining on the surface of the particles to obtain 24.5 g of white powder. It was confirmed by SEM observation (see FIG. 1A) that the obtained powder was plate-like, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Further, when the crystallite size was determined from the peak of the (311) plane observed near 37 degrees using a CALSA detector, it was confirmed to be 72 nm. Furthermore, it was confirmed from the results of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.44% by mass of molybdenum in terms of molybdenum trioxide.
＜実施例２＞スピネル粒子Ｓ－ａ２の合成
　得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１１５０℃まで昇温し、１１５０℃で１０時間保持し焼成を行った以外は、実施例１と同様の操作を行い、２４．５ｇの白色の粉末を得た。得られた粉末はＳＥＭ観察（図１（Ｂ）参照）により板状であり、凝集体が極めて少なく、優れた取り扱い性を有する粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、８２ｎｍであり、実施例１の１０５０℃焼成と比べ、高温で焼成することで結晶成長に有意であることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．４８質量％含むものであることを確認した。 <Example 2> Synthesis of spinel particles S-a2 The obtained mixture was put into a crucible, heated to 1150°C under a condition of 5°C/min in a ceramic electric furnace, and kept at 1150°C for 10 hours for firing. Except for the above, the same operation as in Example 1 was performed to obtain 24.5 g of white powder. It was confirmed by SEM observation (see FIG. 1B) that the obtained powder was plate-like, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Further, the crystallite size was found to be 82 nm from the peak of the (311) plane observed at around 37 degrees using a CALSA detector, and it was 82 nm. Compared with the 1050° C. firing of Example 1, the crystal was obtained by firing at a higher temperature. It was confirmed to be significant for growth. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.48% by mass of molybdenum in terms of molybdenum trioxide.
＜実施例３＞スピネル粒子Ｓ－ａ３の合成
　合成例２で得たα－アルミナ粒子Ａ－２　２０ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇとを乳鉢で混合し、混合物を得た以外は実施例１と同様の操作を行い、２４．６ｇの白色の粉末を得た。得られた粉末の平均粒子径は４．０μｍであり、平均粒子径が合成例１で得たα－アルミナ粒子Ａ－１よりも小さい３．８μｍである合成例２で得たα－アルミナ粒子Ａ－２を用いた場合、実施例１で得た板状スピネル粒子Ｓ－ａ１よりも平均粒子径が小さい粒子が得られた。また、ＳＥＭ観察（図１（Ｃ）参照）により板状であり、凝集体が極めて少なく、優れた取り扱い性を有する粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、７０ｎｍであることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．５３質量％含むものであることを確認した。 Example 3 Synthesis of Spinel Particles Sa3 20 g of α-alumina particles A-2 obtained in Synthesis Example 2 and 7.86 g of magnesium oxide (average particle diameter 3.5 μm, manufactured by Kamijima Chemical Co., Ltd.) were mixed in a mortar. The same operation as in Example 1 was carried out except that a mixture was obtained to obtain 24.6 g of white powder. The average particle size of the obtained powder was 4.0 μm, and the average particle size was 3.8 μm, which was smaller than the α-alumina particles A-1 obtained in Synthesis Example 1, and α-alumina particles obtained in Synthesis Example 2 were obtained. When A-2 was used, particles having an average particle size smaller than that of the plate-like spinel particles Sa1 obtained in Example 1 were obtained. Moreover, it was confirmed by SEM observation (see FIG. 1C) that the particles were plate-shaped, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Moreover, when the crystallite diameter was determined from the peak of the (311) plane observed near 37 degrees using a CALSA detector, it was confirmed to be 70 nm. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.53% by mass of molybdenum in terms of molybdenum trioxide.
＜実施例４＞スピネル粒子Ｓ－ａ４の合成
　合成例１で得たα－アルミナ粒子Ａ－１　２０ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇと、三酸化モリブデン１．６７ｇを乳鉢で混合し、混合物を得た以外は実施例１と同様の操作を行い、２４．６ｇの白色の粉末を得た。得られた粉末はＳＥＭ観察（図１（Ｄ）参照）により板状であり、凝集体が極めて少なく、優れた取り扱い性を有する粒子であることが確認された。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、８８ｎｍであり、実施例２の三酸化モリブデンを添加していない配合で焼成したものと比べ、結晶子径が大きく、三酸化モリブデンが結晶成長に寄与していることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．６１質量％含むものであることを確認した。 Example 4 Synthesis of Spinel Particles S-a4 20 g of α-alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (Kamishima Chemical Co., Ltd. average particle size 3.5 μm), and molybdenum trioxide 1 The same operation as in Example 1 was carried out except that 0.67 g was mixed in a mortar to obtain a mixture, to obtain 24.6 g of a white powder. It was confirmed by SEM observation (see FIG. 1D) that the obtained powder was plate-shaped, had very few aggregates, and had excellent handleability. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Further, the crystallite size was determined from the peak of the (311) plane observed at around 37 degrees using a CALSA detector, and was found to be 88 nm. The crystallite size was calcined in the composition of Example 2 without addition of molybdenum trioxide. It was confirmed that molybdenum trioxide contributed to the crystal growth because the crystallite size was large compared with. Furthermore, it was confirmed from the results of the fluorescent X-ray quantitative analysis that the obtained particles contained molybdenum in an amount of 0.61% by mass in terms of molybdenum trioxide.
＜実施例５＞スピネル粒子Ｓ－ａ５の合成
　合成例１で得たα－アルミナ粒子Ａ－１　２０ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇと、塩化ナトリウム８３．５７ｇを乳鉢で混合し、混合物を得た以外は実施例１と同様の操作を行い、２４．５ｇの白色の粉末を得た。得られた粉末の平均粒子径は８．３μｍであり、塩化ナトリウムを配合することで、実施例２で得た板状スピネル粒子Ｓ－ａ２よりも平均粒子径が大きい粒子が得られた。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、６６ｎｍであることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．３１質量％含むものであることを確認した。 <Example 5> Synthesis of spinel particles S-a5 20 g of α-alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (manufactured by Kamijima Chemical Co., Ltd., average particle diameter 3.5 μm), and sodium chloride 83. The same operation as in Example 1 was carried out except that 57 g was mixed in a mortar to obtain a mixture, and 24.5 g of white powder was obtained. The average particle diameter of the obtained powder was 8.3 μm, and by adding sodium chloride, particles having an average particle diameter larger than that of the plate-like spinel particles Sa2 obtained in Example 2 were obtained. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. In addition, the crystallite size was found to be 66 nm by using a CALSA detector and determining the crystallite size from the peak of the (311) plane observed near 37 degrees. Furthermore, it was confirmed from the result of the quantitative X-ray fluorescence analysis that the obtained particles contained 0.31 mass% of molybdenum in terms of molybdenum trioxide.
＜実施例６＞スピネル粒子Ｓ－ａ６の合成
　合成例１で得たα－アルミナ粒子Ａ－１　２０ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇと、塩化ナトリウム８３．５７ｇを乳鉢で混合し、混合物を得た以外は実施例１と同様の操作を行い、２４．５ｇの白色の粉末を得た。得られた粉末の平均粒子径は８．０μｍであり、実施例５と同様に塩化カリウムを配合することで実施例２で得た板状スピネル粒子Ｓ－ａ２よりも平均粒子径が大きい粒子が得られた。さらに、ＸＲＤ測定を行ったところ、スピネルに由来する鋭いピーク散乱が観察された。また、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ、６８ｎｍであることを確認した。さらに、蛍光Ｘ線定量分析の結果から、得られた粒子は、モリブデンを三酸化モリブデン換算で０．３３質量％含むものであることを確認した。 <Example 6> Synthesis of spinel particles S-a6 20 g of α-alumina particles A-1 obtained in Synthesis Example 1, 7.86 g of magnesium oxide (manufactured by Kamijima Chemical Co., Ltd., average particle diameter 3.5 μm), and sodium chloride 83. The same operation as in Example 1 was carried out except that 57 g was mixed in a mortar to obtain a mixture, and 24.5 g of white powder was obtained. The average particle diameter of the obtained powder was 8.0 μm, and by adding potassium chloride in the same manner as in Example 5, particles having an average particle diameter larger than that of the plate-like spinel particles S-a2 obtained in Example 2 were obtained. Was obtained. Further, when XRD measurement was performed, sharp peak scattering derived from spinel was observed. Further, the crystallite size was found to be 68 nm by using a CALSA detector and determining the crystallite size from the peak of the (311) plane observed at around 37 degrees. Furthermore, it was confirmed from the results of the fluorescent X-ray quantitative analysis that the obtained particles contained 0.33% by mass of molybdenum in terms of molybdenum trioxide.
＜比較例１＞スピネル粒子Ｓ－ｂ１の合成
　市販のベーマイト（粒子径２μｍ）２３．５３ｇと、酸化マグネシウム（神島化学製　平均粒子径３．５μｍ）７．８６ｇとを乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１１５０℃まで昇温し、１１５０℃で１０時間保持し焼成を行なった。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、２７．６ｇの白色の粉末を得た。得られた粉末を乳鉢で、１５０μｍ篩を通るまで解砕した。続いて、得られた前記白色粉末の２５ｇと２％硝酸の１００ｍＬを配合し、直径５ｍｍのアルミナビーズを加え、ペイントコンディショナーで２０分解砕を行った。その後、分散溶液をろ過により２％硝酸を除き、水洗浄と乾燥を行い、２４．６ｇの白色の粉末を得た。得られた粉末をＳＥＭで観察したところ（図１（Ｅ）参照）、板状であったが、粒子形状や粒子径が不揃いであった。また、板の厚み平均が１μｍで、レーザー回折式粒度分布計より求められる平均粒子径が２．９μｍであり、平均粒子径／厚み平均より求められるアスペクト比が２．９と、実施例１～６で得た板状スピネル粒子のアスペクト比と比べて、極端に小さい値となった。さらに、ＸＲＤ測定を行ったところ、スピネルに由来するピーク散乱が観察されたが、実施例１～６で得た板状スピネル粒子の測定結果と比べて、ピークがブロードであり、ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ２８ｎｍであり、実施例１～６で得た板状スピネル粒子の結晶子径と比較して、極端に小さい値となった。 Comparative Example 1 Synthesis of Spinel Particle S-b1 23.53 g of commercially available boehmite (particle diameter 2 μm) and 7.86 g of magnesium oxide (average particle diameter 3.5 μm manufactured by Kamijima Chemical Co., Ltd.) were mixed in a mortar, and the mixture was mixed. Obtained. The obtained mixture was put into a crucible, heated to 1150° C. under a condition of 5° C./min in a ceramic electric furnace, and kept at 1150° C. for 10 hours for firing. After that, the temperature was lowered to room temperature under the condition of 5° C./minute, and then the crucible was taken out to obtain 27.6 g of white powder. The obtained powder was crushed in a mortar until it passed through a 150 μm sieve. Subsequently, 25 g of the obtained white powder and 100 mL of 2% nitric acid were blended, alumina beads having a diameter of 5 mm were added, and 20 pieces were crushed and crushed with a paint conditioner. Then, the dispersed solution was filtered to remove 2% nitric acid, washed with water and dried to obtain 24.6 g of white powder. When the obtained powder was observed by SEM (see FIG. 1(E)), it was plate-shaped, but the particle shape and particle diameter were uneven. Further, the average thickness of the plate was 1 μm, the average particle size determined by a laser diffraction type particle size distribution meter was 2.9 μm, and the aspect ratio determined by the average particle size/thickness average was 2.9. The value was extremely smaller than the aspect ratio of the plate-like spinel particles obtained in No. 6. Further, when XRD measurement was carried out, peak scattering derived from spinel was observed, but the peak was broader than that of the plate-like spinel particles obtained in Examples 1 to 6, and the peak was broadened. When used, the crystallite diameter was found to be 28 nm from the peak of the (311) plane observed at around 37 degrees, which was extremely smaller than the crystallite diameter of the plate-like spinel particles obtained in Examples 1 to 6. It became a value.
＜比較例２＞スピネル粒子Ｓ－ｂ２の合成
　市販のスピネル粒子（平均粒子径２０μｍに篩分級で調整されたもの）２５ｇに、径５ｍｍのアルミナビーズ２５ｇを加えペイントコンディショナーを用い解砕を行い、２４．７ｇのスピネル粒子粉末を得た。得られた粉末をＳＥＭで観察したところ（図１（Ｆ）参照）、粒子形状や粒子径が不揃いな角状粒子であった。また、板の厚み平均が５．３μｍで、レーザー回折式粒度分布計より求められる平均粒子径が５．５μｍであり、平均粒子径／厚み平均より求められるアスペクト比が１．０と、実施例１～６で得た板状スピネル粒子のアスペクト比と比べて、極端に小さい値となった。さらに、ＸＲＤ測定を行ったところ、スピネルに由来するピーク散乱が観察された。ＣＡＬＳＡ検出器を用い、３７度付近に認められる（３１１）面のピークより結晶子径を求めたところ８８ｎｍであった。 <Comparative Example 2> Synthesis of spinel particles S-b2 To 25 g of commercially available spinel particles (adjusted by sieving to an average particle diameter of 20 μm), 25 g of alumina beads having a diameter of 5 mm was added and crushed using a paint conditioner, 24.7 g of spinel particle powder was obtained. When the obtained powder was observed by SEM (see FIG. 1(F)), it was found to be angular particles having irregular particle shapes and particle sizes. Further, the average thickness of the plate was 5.3 μm, the average particle diameter obtained by a laser diffraction type particle size distribution meter was 5.5 μm, and the aspect ratio obtained by the average particle diameter/thickness average was 1.0. The value was extremely smaller than the aspect ratio of the plate-like spinel particles obtained in 1 to 6. Further, when XRD measurement was performed, peak scattering derived from spinel was observed. Using a CALSA detector, the crystallite size was found to be 88 nm from the peak of the (311) plane observed at around 37 degrees.
≪評価方法≫
　上記合成例で得られたα－アルミナ粒子、並びに、上記実施例及び比較例で得られたスピネル粒子を試料として、以下の評価を行った。具体的な測定方法を以下に示す。また、評価結果を表１に示す。 ≪Evaluation method≫
The α-alumina particles obtained in the above synthesis example and the spinel particles obtained in the above examples and comparative examples were used as samples for the following evaluations. The specific measuring method is shown below. The evaluation results are shown in Table 1.
＜合成例で得られたα－アルミナ粒子の評価＞
［α―アルミナ粒子の平均粒子径Ｌの計測］
　作製した試料について、レーザー回折式粒度分布計ＨＥＬＯＳ（Ｈ３３５５）＆ＲＯＤＯＳ（株式会社日本レーザー製）を用い、分散圧３ｂａｒ、引圧９０ｍｂａｒの条件で平均粒子径ｄ５０（μｍ）を求め、平均粒子径Ｌとした。 <Evaluation of α-alumina particles obtained in Synthesis Example>
[Measurement of average particle size L of α-alumina particles]
The average particle diameter d50 (μm) of the prepared sample was calculated using a laser diffraction particle size distribution analyzer HELOS (H3355) & RODOS (manufactured by Nippon Laser Co., Ltd.) under the conditions of a dispersion pressure of 3 bar and a suction pressure of 90 mbar, and the average particle diameter L And
［α化率の分析］
　作製した試料を０．５ｍｍ深さの測定試料用ホルダーにのせ、一定荷重で平らになるように充填し、それを広角Ｘ線回折装置（株式会社リガク製 Ｒｉｎｔ－Ｕｌｔｍａ）にセットし、Ｃｕ／Ｋα線、４０ｋＶ／３０ｍＡ、スキャンスピード２度／分、走査範囲１０度以上７０度以下の条件で測定を行った。α－アルミナと遷移アルミナの最強ピーク高さの比よりα化率を求めた。 [Analysis rate analysis]
The prepared sample is placed on a holder for a measurement sample having a depth of 0.5 mm and filled so as to be flat with a constant load, and the sample is set in a wide-angle X-ray diffractometer (Rint-Ultma manufactured by Rigaku Corporation), and Cu/ The measurement was performed under the conditions of Kα ray, 40 kV/30 mA, scan speed 2°/min, and scanning range 10° or more and 70° or less. The α conversion rate was calculated from the ratio of the strongest peak heights of α-alumina and transition alumina.
［α－アルミナ粒子内に含まれるＭｏ量の分析］
　蛍光Ｘ線分析装置ＰｒｉｍｕｓＩＶ(株式会社リガク製) を用い、作製した試料約７０ｍｇをろ紙にとり、ＰＰフィルムをかぶせて組成分析を行った。ＸＲＦ分析結果により求められるモリブデン量を、板状アルミナ粒子１００質量％に対する三酸化モリブデン換算（質量％）により求めた。 [Analysis of the amount of Mo contained in α-alumina particles]
Approximately 70 mg of the prepared sample was placed on a filter paper using a fluorescent X-ray analyzer Primus IV (manufactured by Rigaku Corporation), and a PP film was covered to analyze the composition. The amount of molybdenum determined by the XRF analysis result was determined by converting to molybdenum trioxide (% by mass) based on 100% by mass of the plate-shaped alumina particles.
［密度の測定］
　作製した試料を、３００℃３時間の条件で前処理を行った後、マイクロメリティックス社製　乾式自動密度計アキュピックＩＩ１３３０を用いて、測定温度２５℃、ヘリウムをキャリアガスとして使用した条件で測定した。 [Measurement of density]
The prepared sample is pretreated under the condition of 300° C. for 3 hours, and then measured using a dry automatic densimeter Acupic II 1330 manufactured by Micromeritics under the conditions of measuring temperature of 25° C. and using helium as a carrier gas. did.
＜実施例及び比較例で得られたスピネル粒子の評価＞
［スピネル粒子の平均粒子径Ｌの計測］
　作製した試料について、レーザー回折式粒度分布計ＨＥＬＯＳ（Ｈ３３５５）＆ＲＯＤＯＳ（株式会社日本レーザー製）を用い、分散圧３ｂａｒ、引圧９０ｍｂａｒの条件で平均粒子径ｄ５０（μｍ）を求め、平均粒子径Ｌとした。 <Evaluation of Spinel Particles Obtained in Examples and Comparative Examples>
[Measurement of average particle diameter L of spinel particles]
The average particle diameter d50 (μm) of the prepared sample was calculated using a laser diffraction particle size distribution analyzer HELOS (H3355) & RODOS (manufactured by Nippon Laser Co., Ltd.) under the conditions of a dispersion pressure of 3 bar and a suction pressure of 90 mbar, and the average particle diameter L And
［スピネル粒子の厚みＴの計測］
　作製した試料について、走査型電子顕微鏡（ＳＥＭ）を用いて、５０個の厚みを測定した平均値を採用し、厚みＴ（μｍ）とした。 [Measurement of thickness T of spinel particles]
With respect to the produced sample, an average value of 50 thicknesses measured by using a scanning electron microscope (SEM) was adopted as a thickness T (μm).
［アスペクト比Ｌ／Ｔ］
　スピネル粒子のアスペクト比は下記の式を用いて求めた。 [Aspect ratio L/T]
The aspect ratio of the spinel particles was calculated using the following formula.
　アスペクト比　＝　板状スピネル粒子の平均粒子径Ｌ／板状スピネル粒子の厚みＴ Aspect ratio = average particle diameter L of plate-like spinel particles/thickness T of plate-like spinel particles
［スピネル結晶の分析］
　作製した試料を０．５ｍｍ深さの測定試料用ホルダーにのせ、一定荷重で平らになるように充填し、それを広角Ｘ線回折（ＸＲＤ）装置（株式会社リガク製 Ｒｉｎｔ－Ｕｌｔｍａ）にセットし、Ｃｕ／Ｋα線、４０ｋＶ／３０ｍＡ、スキャンスピード２度／分、走査範囲１０度以上７０度以下の条件で測定を行った。 [Analysis of spinel crystals]
The prepared sample is placed on a holder for a measurement sample having a depth of 0.5 mm and filled so as to be flat with a constant load, and the sample is set in a wide-angle X-ray diffraction (XRD) device (Rint-Ultma manufactured by Rigaku Corporation). , Cu/Kα ray, 40 kV/30 mA, scan speed of 2°/min, and scanning range of 10° to 70°.
［結晶子径の測定］
　株式会社リガク製　Ｘ線回折装置ＳｍａｒｔＬａｂ、検出器ＣＡＬＳＡを用い、以下の条件で３７度付近に認められるピークより、（３１１）面の結晶子径（ｎｍ）を求めた。 [Measurement of crystallite size]
The crystallite diameter (nm) of the (311) plane was determined from the peak observed at around 37 degrees under the following conditions using an X-ray diffractometer SmartLab manufactured by Rigaku Corporation and a detector CALSA.
（測定条件）
２θ／θ法　２θ＝１５ｄｅｇ以上８０ｄｅｇ以下
ｓｔｅｐ数　０．００２ｄｅｇ
スキャンスピード０．０５ｄｅｇ．／ｍｉｎ．
βｓ＝２０ｒｐｍ
Ｓｏｌｌｅｒ／ＰＳＣ＝２．５ｄｅｇ．ｓｈｏｒｔ
Ｓｏｌｌｅｒ＝２．５ｄｅｇ． (Measurement condition)
2θ/θ method 2θ=15 deg or more and 80 deg or less step number 0.002 deg
Scan speed 0.05 deg. /Min.
βs=20 rpm
Soller/PSC=2.5 deg. short
Soller=2.5 deg.
［密度の測定］
　作製した試料を、３００℃３時間の条件で前処理を行った後、マイクロメリティックス社製　乾式自動密度計アキュピックＩＩ１３３０を用いて、測定温度２５℃、ヘリウムをキャリアガスとして使用した条件で測定した。 [Measurement of density]
The prepared sample is pretreated under the condition of 300° C. for 3 hours, and then measured using a dry automatic densimeter Acupic II 1330 manufactured by Micromeritics under the conditions of measuring temperature of 25° C. and using helium as a carrier gas. did.
［誘電率・誘電正接の測定］
　作製した試料に２５ｇに径５ｍｍのアルミナビーズを加え、ペイントコンディショナーで４時間処理し、スピネル粒子を粉砕した。粉砕したスピネル粒子を用い、ベクトルネットワークアナライザＥ８３６１Ａを用い、摂動方式共振器法、周波数１ＧＨｚ、温度２５℃、湿度５０％の条件で比誘電率・誘電正接を求めた。 [Measurement of dielectric constant and loss tangent]
Alumina beads having a diameter of 5 mm were added to 25 g of the prepared sample and treated with a paint conditioner for 4 hours to pulverize the spinel particles. Using the pulverized spinel particles and a vector network analyzer E8361A, the relative permittivity and dielectric loss tangent were determined under the conditions of perturbation type resonator method, frequency 1 GHz, temperature 25° C. and humidity 50%.
［曲げ応力］
　作製した試料を６６ｗｔ％、ポリフェニレンサルファイト樹脂（ＰＰＳ樹脂　ＤＩＣ製ＭＡ－５００）３４ｗｔ％となるように配合し、計２０ｇの混合物を準備した。混合物２０ｇをフルフライトのスクリューを設置した二軸混練機を用いて、押出機温度３００℃、スクリュー回転数１５０ｒｐｍの条件で２分間溶融混練を行った。得られた混練物をダイスからストランド状で取り出し、ペレット化したのち、小型射出成形機を用いて幅５ｍｍ、長さ７５ｍｍ、厚み１ｍｍのダンベル試験片を得た。得られた試験片を用いて、支点間距離が３２ｍｍとなるように、２点で支持し、これと対向する辺における上記２点の中間位置にクロスヘッドの移動速度１ｍｍ／分の速度で加重を加えて、試験片が破壊したときの最大荷重を測定し、３点曲げ強度（ＭＰａ）を算出した。当該曲げ強度を５点測定して平均値を求めた。 [Bending stress]
The prepared sample was blended in an amount of 66 wt% and a polyphenylene sulfite resin (PPS resin DIC MA-500) 34 wt% to prepare a total of 20 g of a mixture. 20 g of the mixture was melt-kneaded for 2 minutes under the conditions of an extruder temperature of 300° C. and a screw rotation speed of 150 rpm using a twin-screw kneader equipped with a full flight screw. The obtained kneaded product was taken out from the die in a strand form, pelletized, and then, using a small injection molding machine, a dumbbell test piece having a width of 5 mm, a length of 75 mm and a thickness of 1 mm was obtained. Using the obtained test piece, it is supported at two points so that the distance between fulcrums is 32 mm, and the crosshead is moved at a moving speed of 1 mm/min at an intermediate position between the two points on the side opposite to this. Was added to measure the maximum load when the test piece was broken, and the three-point bending strength (MPa) was calculated. The bending strength was measured at 5 points and an average value was obtained.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１から、実施例１で得たスピネル粒子Ｓ－ａ１と実施例２で得たスピネル粒子Ｓ－ａ２、実施例２で得たスピネル粒子Ｓ－ａ２と実施例４で得たスピネル粒子Ｓ－ａ４の比較により、結晶子径が大きいほど、曲げ応力（曲げ強度）が高くなる傾向がみられた。
　また、実施例２で得たスピネル粒子Ｓ－ａ２と、実施例５で得たスピネル粒子Ｓ－ａ５と、実施例６で得たスピネル粒子Ｓ－ａ６の比較により、アスペクト比が大きいほど曲げ応力（曲げ強度）が高くなる傾向がみられた。 From Table 1, the spinel particles S-a1 obtained in Example 1 and the spinel particles S-a2 obtained in Example 2, the spinel particles S-a2 obtained in Example 2 and the spinel particles S-obtained in Example 4 were found. By comparing a4, it was found that the larger the crystallite diameter, the higher the bending stress (bending strength).
Further, by comparing the spinel particles S-a2 obtained in Example 2, the spinel particles S-a5 obtained in Example 5, and the spinel particles S-a6 obtained in Example 6, the bending stress increases as the aspect ratio increases. (Bending strength) tended to increase.
　これに対し、比較例１で得たスピネル粒子Ｓ－ｂ１及び比較例２で得たスピネル粒子Ｓｂ－２では、実施例１～６で得たスピネル粒子Ｓ－ａ１～Ｓ－ａ６よりもアスペクト比が小さく、特に比較例１で得たスピネル粒子Ｓ－ｂ１は結晶子径も小さく、曲げ応力が著しく低い結果であった。 In contrast, the spinel particles S-b1 obtained in Comparative Example 1 and the spinel particles Sb-2 obtained in Comparative Example 2 had an aspect ratio higher than that of the spinel particles S-a1 to S-a6 obtained in Examples 1 to 6. Was small, and especially the spinel particles S-b1 obtained in Comparative Example 1 had a small crystallite size, resulting in a remarkably low bending stress.
　以上のことから、本実施形態のスピネル粒子は、高アスペクト比であることで、誘電率や誘電正接等の特有の性能を保ちながら、力学特性に優れることが示された。 From the above, it was shown that the spinel particles of the present embodiment have a high aspect ratio and thus have excellent mechanical properties while maintaining peculiar properties such as dielectric constant and dielectric loss tangent.
　本実施形態の板状スピネル粒子及びその製造方法によれば、誘電正接を低く保ちながら、優れた機械強度を有する板状スピネル粒子を提供することができる。 According to the plate-like spinel particles and the manufacturing method thereof of the present embodiment, it is possible to provide plate-like spinel particles having excellent mechanical strength while keeping the dielectric loss tangent low.

Claims (9)

  1. 　厚みＴが０．０１μｍ以上５μｍ以下であり、平均粒子径Ｌが０．１μｍ以上５００μｍ以下であり、アスペクト比（Ｌ／Ｔ）が３以上５００以下であり、かつ粒子内にモリブデンを含む、板状スピネル粒子。 A plate having a thickness T of 0.01 μm or more and 5 μm or less, an average particle diameter L of 0.1 μm or more and 500 μm or less, an aspect ratio (L/T) of 3 or more and 500 or less, and containing molybdenum in the particles. Spinel particles.
  2. 　前記モリブデンの含有量が、板状スピネル粒子１００質量％に対して三酸化モリブデン換算で０．０１質量％以上１質量％以下である、請求項１に記載の板状スピネル粒子。 The plate-shaped spinel particles according to claim 1, wherein the content of the molybdenum is 0.01% by mass or more and 1% by mass or less in terms of molybdenum trioxide with respect to 100% by mass of the plate-shaped spinel particles.
  3. 　Ｘ線回折法により得られる回折ピークの、（３１１）面に相当するピークの半値幅から算出される結晶子径が６０ｎｍ以上である、請求項１又は２に記載の板状スピネル粒子。 The plate-like spinel particles according to claim 1 or 2, wherein the crystallite diameter calculated from the half width of the peak corresponding to the (311) plane of the diffraction peak obtained by the X-ray diffraction method is 60 nm or more.
  4. 　請求項１～３のいずれか一項に記載の板状スピネル粒子の製造方法であって、
    　マグネシウム化合物及びアルミニウム化合物を、モリブデン存在下で、焼成させる、製造方法。     The method for producing plate-shaped spinel particles according to any one of claims 1 to 3,
    A method for producing, which comprises firing a magnesium compound and an aluminum compound in the presence of molybdenum.
  5. 　前記アルミニウム化合物が板状アルミナ粒子である、請求項４に記載の製造方法。 The manufacturing method according to claim 4, wherein the aluminum compound is plate-like alumina particles.
  6. 　前記アルミニウム化合物がモリブデンを三酸化モリブデン換算で０．１質量％以上１質量％以下含む、請求項４又は５に記載の製造方法。 The method according to claim 4 or 5, wherein the aluminum compound contains molybdenum in an amount of 0.1% by mass or more and 1% by mass or less in terms of molybdenum trioxide.
  7. 　焼成時に形状制御剤としてナトリウム化合物又はカリウム化合物を用いる、請求項４～６のいずれか一項に記載の製造方法。 The production method according to any one of claims 4 to 6, wherein a sodium compound or a potassium compound is used as a shape control agent during firing.
  8. 　１３００℃未満で焼成させる、請求項４～７のいずれか一項に記載の製造方法。 The manufacturing method according to any one of claims 4 to 7, wherein firing is performed at a temperature lower than 1300°C.
  9. 　前記アルミニウム化合物及び前記マグネシウム化合物の平均粒子径が１μｍ以上１０μｍ以下である、請求項４～８のいずれか一項に記載の製造方法。 The production method according to any one of claims 4 to 8, wherein the aluminum compound and the magnesium compound have an average particle diameter of 1 µm or more and 10 µm or less.
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