WO2020004644A1 - Nanocrystal and method for manufacturing same, and electronic device and piezoelectric element using nanocrystal - Google Patents

Nanocrystal and method for manufacturing same, and electronic device and piezoelectric element using nanocrystal Download PDF

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WO2020004644A1
WO2020004644A1 PCT/JP2019/025911 JP2019025911W WO2020004644A1 WO 2020004644 A1 WO2020004644 A1 WO 2020004644A1 JP 2019025911 W JP2019025911 W JP 2019025911W WO 2020004644 A1 WO2020004644 A1 WO 2020004644A1
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nanocrystal
nanocrystals
solution
sheet
plane
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French (fr)
Japanese (ja)
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瑶子 ▲高▼田
憲一 三村
加藤　一実
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国立研究開発法人産業技術総合研究所
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Priority to JP2020527696A priority Critical patent/JP7109108B2/en
Publication of WO2020004644A1 publication Critical patent/WO2020004644A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G25/00—Compounds of zirconium
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C30B29/32—Titanates; Germanates; Molybdates; Tungstates
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C30B29/64—Flat crystals, e.g. plates, strips or discs
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C30B29/66—Crystals of complex geometrical shape, e.g. tubes, cylinders
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • C30B7/10—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions by application of pressure, e.g. hydrothermal processes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/09—Forming piezoelectric or electrostrictive materials
    • H10N30/093—Forming inorganic materials
    • H10N30/097—Forming inorganic materials by sintering
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/853—Ceramic compositions

Definitions

  • the present invention relates to a nanocrystal and a method for producing the same, and an electronic device and a piezoelectric element using the nanocrystal.
  • PZT Lead zirconate titanate Pb (Zr x Ti 1-x ) O 3 (0 ⁇ x ⁇ 1)
  • PZT which is a metal oxide is composed of lead titanate PbTiO 3 (PT) and lead zirconate PbZrO 3 (PZ).
  • PT lead titanate PbTiO 3
  • PZ lead zirconate PbZrO 3
  • ferroelectric having a perovskite crystal structure.
  • piezoelectric material exhibiting an excellent piezoelectric effect.
  • Such nanocrystals of lead zirconate titanate, lead titanate, and lead zirconate are expected to be applied as novel materials capable of expressing characteristic physical properties due to size.
  • PZT Lead zirconate titanate
  • sol-gel method an organic metal thermal decomposition method
  • organic metal vapor phase epitaxy method an organic metal vapor phase epitaxy method.
  • the crystallization temperature of the PZT thin film requires a firing temperature of about 600 ° C. or more, device degradation due to high-temperature processing such as diffusion or reaction at the PZT film / Si substrate interface is a problem.
  • lead contained in PZT is a volatile substance, and compositional deviation between a starting material and a formed film is apt to occur and composition control is difficult.
  • the production of PZT films by the method has attracted attention.
  • nano-sized single crystals with controlled shapes are known in recent years because they are known to exhibit characteristics different from those of bulk.
  • a PZT particle having a size of 0.5 ⁇ m to 10 ⁇ m, that is, a micron size, and having a shape of a cube, a rectangular parallelepiped, or a truncated octahedron, and a method for producing the same have already been reported (Patent Document 3). reference).
  • Patent Document 3 Patent Document 3
  • the crystal orientation is not reported, and there are few reports on the synthesis, morphology control, and crystal structure of nano-sized PZT crystals.
  • the size is smaller than the micron size, for example, the size is about several tens nm to several hundreds nm. Therefore, lead zirconate titanate and titanate of this size are used. There is a demand for stable production of lead and lead zirconate nanocrystals.
  • the present invention has been made in view of the above situation, and has been made in view of the above circumstances, and has a nanocrystal having at least one of a (100) plane, a (010) plane, and a (001) plane as a facet, a method for producing the same, and a nanocrystal. It is an object to provide an electronic device and a piezoelectric element using a crystal.
  • the present inventor has a (100) face, a (010) face, or a (001) facet, and has a high crystallinity of lead zirconate titanate, lead titanate, and lead zirconate. Successful synthesis of nanocrystals led to the present invention.
  • the present invention provides the following means in order to solve the above problems.
  • the nanocrystal according to the first embodiment of the present invention is a single crystal represented by Pb (Zr, Ti) O 3 and has at least one of a (100) plane, a (010) plane, and a (001) plane. One of them is a facet, and the size is 1 nm or more and 1000 nm or less.
  • the shape of the crystal may be any of a sheet-like shape, a substantially hexahedral shape, or a partially sheet-like and partially substantially hexahedral shape.
  • a step may be provided on a side surface of the sheet.
  • the method for producing a nanocrystal according to the second aspect of the present invention comprises the steps of: preparing a precursor solution using lead (II) acetate trihydrate, a water-soluble titanium complex aqueous solution and a water-soluble zirconium complex aqueous solution as starting materials, The method includes a step of performing heat synthesis using a mixed solution of an aqueous solution of sodium hydroxide and an organic carboxylic acid.
  • the ligand of the water-soluble zirconium complex may be a hydroxycarboxylic acid.
  • the method for producing nanocrystals according to the third aspect of the present invention comprises the steps of: adding an aqueous sodium hydroxide solution to lead (II) acetate trihydrate, and then adding an aqueous solution of a water-soluble titanium complex, an amine compound, and an organic carboxylic acid. And heat-synthesizing using a solution in which is mixed.
  • the ligand of the water-soluble titanium complex may be a hydroxycarboxylic acid.
  • the organic carboxylic acid may be oleic acid.
  • the concentration of the aqueous sodium hydroxide solution may be 1 mol / L or more and 10 mol / L or less.
  • the number of moles of the organic carboxylic acid per mole of lead in the solution may be from 1 to 30.
  • the heating may be performed at a temperature of 140 ° C or more and 290 ° C or less.
  • the heating may be performed for 1 hour or more and 80 hours or less.
  • a step of centrifuging the solution after the heating may be included.
  • An electronic device includes the thin film including the nanocrystal according to the above aspect.
  • a piezoelectric element according to a fifth aspect of the present invention includes the thin film containing the nanocrystal according to the above aspect, and a pair of electrodes provided so as to sandwich the thin film.
  • nanocrystal of the present invention it is possible to provide a nanocrystal that has at least one of the (100) plane, the (010) plane, and the (001) plane as a facet and is expected to have properties different from those of a bulk.
  • 3 is an SEM image of the surface of a sample produced by drop-drying the dispersion containing lead zirconate titanate nanocrystals produced in Example 1 on a silicon wafer substrate at room temperature.
  • 3 is a powder X-ray diffraction (XRD) pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 1.
  • 2 is a high-magnification TEM image of the lead zirconate titanate nanocrystals produced in Example 1.
  • 3 is a TEM image of lead zirconate titanate nanocrystals produced in Example 1.
  • 3 is an electron diffraction pattern of a lead zirconate titanate nanocrystal prepared in Example 1.
  • FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention.
  • 9 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing nanocrystals of lead zirconate titanate manufactured in Example 2 on a silicon wafer substrate at room temperature.
  • 5 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 2.
  • 9 is an SEM image of the surface of a sample manufactured by drop drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 3 on a silicon wafer substrate at room temperature.
  • 9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 3.
  • 9 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing nanocrystals of lead zirconate titanate manufactured in Example 4 on a silicon wafer substrate at room temperature.
  • FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention.
  • 9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 4.
  • FIG. 11 is an SEM image of the surface of a sample prepared by drop drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 5 on a silicon wafer substrate at room temperature.
  • FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention.
  • 9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 5.
  • 11 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing lead titanate nanocrystals manufactured in Example 6 on a silicon wafer substrate at room temperature.
  • 9 is a powder XRD pattern of a sample containing lead titanate nanocrystals prepared in Example 6.
  • 11 is an SEM image of a sample surface of a lead zirconate titanate nanocrystal film produced in Example 7.
  • 11 is an SEM image of a sample surface of a lead zirconate titanate nanocrystal film produced in Example 7.
  • 9 is an XRD pattern of a sample of a lead zirconate titanate nanocrystal film prepared in Example 7.
  • the sample of the lead zirconate titanate nanocrystal film prepared in Example 7 was subjected to a heat treatment at 600 ° C., and then measured by using a piezoelectric response microscope to obtain a piezoelectric constant-applied voltage (d33 -PFM- V) curve. is there.
  • the nanocrystal of the present invention is a single crystal represented by Pb (Zr, Ti) O 3 and has at least one of a (100) plane, a (010) plane, and a (001) plane as a facet. That is, the nanocrystal of the present embodiment has at least one of the (100) plane, the (010) plane, and the (001) plane, which are flat planes, as facets.
  • the size of the nanocrystal of the present embodiment is 1 nm or more and 1000 nm or less, preferably 3 nm or more and 900 nm or less, and more preferably 5 nm or more and 750 nm or less.
  • PZT is a mixed crystal of ferroelectric lead titanate and antiferroelectric lead zirconate.
  • the PZT crystal structure has a perovskite structure.
  • Lead titanate (PT) is tetragonal
  • PZ lead zirconate
  • the nanocrystal of the present invention has a tetragonal or substantially tetragonal perovskite structure, a rhombohedral or substantially rhombohedral perovskite structure, or the like, depending on the composition, and has a (100) plane, a (010) plane, and a (100) plane. 001) as at least one facet.
  • the shape of the nanocrystal according to the present embodiment may be a sheet shape, a substantially hexahedral shape, or a shape having a partially sheet shape and a partially substantially hexahedral shape.
  • the sheet-shaped nanocrystal is a nanocrystal whose size in the thickness direction is smaller than the size in the surface spreading direction, and is not limited, but as a guide, the size of the surface spreading direction is The case where the ratio between the maximum size and the size in the thickness direction has a difference of more than 3: 1.
  • the ratio between the maximum size and the size in the thickness direction may have a difference of more than 5: 1 or may have a difference of more than 10: 1, There may be a difference of more than 20: 1.
  • a typical sheet-shaped nanocrystal is shown based on an SEM image of FIG. 7 described later.
  • the nanocrystal located substantially at the center is a sheet-shaped nanocrystal.
  • the sheet-shaped nanocrystal has, for example, a shape as shown on the right side of the SEM image in FIG. 7 and a shape as shown in FIG. 11B.
  • the orientation can be easily controlled when integrated on a substrate.
  • the nanocrystal described in the present embodiment is preferably in the form of a sheet in that it has a large specific surface area, high adhesion to an interface between the nanocrystal and the nanocrystal or a base material, and downsizing of the element is possible.
  • FIG. 4C schematically shows a perspective view of a partially-sheet-shaped and partially hexahedral-shaped nanocrystal.
  • the nanocrystal 1 ⁇ / b> A schematically shown in FIG. 4C has a sheet-shaped sheet portion 2 and a hexahedral hexahedral portion 3 located on the sheet portion 10.
  • the hexahedral shape portion 3 may not be strictly a hexahedral shape but may be a substantially hexahedral shape since one surface is in contact with the sheet-like portion 2.
  • the nanocrystal 1A schematically shown in FIG. 4C has a plurality of step structures 21 described later on the side surface 20 of the sheet-like portion 2.
  • the angle between the side surface that intersects the side surface and the side surface among the surfaces forming the step structure 21 can be an arbitrary angle.
  • FIG. 4C illustrates the nanocrystal 1A having one hexahedral shape portion 3, the present invention is not limited to this example, and the nanocrystal 1A can have an arbitrary number of hexahedral shape portions 3.
  • FIG. 4C shows only a part of the example of the facet surface.
  • a 3 , A 4 , A 5 , A 6 , and A 7 shown in FIG. 4C are facet planes, respectively.
  • the nanocrystal 1A shown in FIG. 4C has facets on any of the (001), (010), and (100) planes. Specifically, if A 3 is a facet of the (100) plane, A 4 and A 7 are facets of the (010) plane, and A 5 and A 6 are facets of the (001) plane. That is, the nanocrystal 1A has a facet in any of the (100) plane, the (010) plane, and the (001) plane.
  • This embodiment is not limited to this example, and it is sufficient that at least one of the (100) plane, the (010) plane, and the (001) plane is provided as a facet.
  • the surface of the nanocrystal of this embodiment may consist of only a plurality of flat surfaces as long as it has at least one of the (100) plane, the (010) plane and the (001) plane as a facet.
  • a flat surface and a curved surface may be combined.
  • the angle between adjacent surfaces may be acute or obtuse.
  • One nanocrystal may have one shape or a shape combining two or more arbitrarily selected from the group consisting of a hexahedral shape, a substantially hexahedral shape, and a sheet-like shape.
  • each shape and the ratio of length, width, and thickness can be arbitrarily selected.
  • different shapes having different sizes and different ratios may be included in one nanocrystal. All may have the same size or the same shape.
  • the above shape may be confirmed using a scanning electron microscope, a transmission electron microscope, or the like.
  • the nanocrystal is not only a hexahedral or substantially hexahedral crystal, but also an incomplete hexahedral crystal in which the vertices of the hexahedron are chamfered.
  • nanocrystals of approximately hexahedral shape are not only hexahedral or approximately hexahedral crystals that are synthesized at the stage when nanocrystal synthesis is sufficiently advanced, but also incomplete hexahedral shapes in which the vertices of the hexahedron are chamfered.
  • FIG. 4C is a perspective view schematically illustrating a nanocrystal having a substantially hexahedral shape.
  • FIG. 9B shows a perspective view of a typical example of a substantially hexahedral nanocrystal.
  • the substantially hexahedral nanocrystal shown in FIG. 9B is an incomplete hexahedral crystal 1A in which at least one vertex of the hexahedron is chamfered.
  • the substantially hexahedral nanocrystal 1B shown in FIG. 9B has a chamfer 10 and a facet.
  • the nanocrystal 1B shown in FIG. 9B shows facets A 8 , A 9 , A 10 , and A 11 which are a part of the facet.
  • the sheet-like nanocrystal may have a step on a side surface.
  • Each step of the step may extend in the thickness direction of the sheet-like nanocrystal, and each step may be arranged along the outer periphery of the sheet-like nanocrystal.
  • Each step of the step may be composed of any one of the (100) plane, the (010) plane, and the (001) plane.
  • the nanocrystal according to the present embodiment is partially sheet-like and partially substantially hexahedral, the nanocrystal may have a step 21 on the side surface 20 of the sheet-like portion 2.
  • Each step of the step 20 may extend in the thickness direction of the sheet-like portion 2, and each step may be arranged along the outer periphery of the sheet-like portion.
  • Each step of the step 20 may be composed of any one of the (100) plane, the (010) plane, and the (001) plane.
  • a typical step is shown based on a SEM image of FIG.
  • the diagram shown on the right side of the SEM image in FIG. 11A shows a part of the side surface of the sheet portion of the nanocrystal located at the lower center in FIG. 11A, and shows two steps. did.
  • the size of the nanocrystal of the present invention is 1 nm or more and 1000 nm or less.
  • the size of the nanocrystal is preferably from 1 nm to 800 nm, more preferably from 1 nm to 500 nm, and still more preferably from 1 nm to 200 nm. Further, depending on the use, it is preferable that the thickness be 1 nm or more and 100 nm or less, and it is more preferable that the thickness be 1 nm or more and 50 nm or less.
  • the size of the electronic device can be reduced by using a nanocrystal having a size of 1 nm to 100 nm.
  • the size of the nanocrystal means the largest distance (length) of the distance connecting two separated points on the outer periphery of the electron microscope image (SEM image, TEM image, etc.) of the nanocrystal. I do. In other words, it means the longest length of two points of the nanocrystal in an electron microscope image (SEM image, TEM image, etc.) of the nanocrystal.
  • the method for producing nanocrystals according to the present embodiment includes a method for producing nanocrystals of lead zirconate titanate Pb (Zr x Ti 1-x ) O 3 (0 ⁇ x ⁇ 1) (PZT) using lead acetate (II).
  • a nanocrystal having at least one of the (100) plane, the (010) plane, and the (001) plane as a facet can be stably manufactured.
  • an amine compound may be mixed with the precursor solution in addition to the aqueous sodium hydroxide solution and the organic carboxylic acid.
  • a water-soluble titanium complex and a water-soluble zirconium complex are mixed in the above-mentioned mixed solution by adjusting the molar ratio of titanium and zirconium so that the desired composition is obtained. I do.
  • a nanocrystal having an arbitrary composition can be synthesized.
  • the molar ratio of zirconium is set to 0 when synthesizing lead titanate PbTiO 3 (PT) nanocrystals, and the molar ratio of titanium is set to 0 when synthesizing lead zirconate PbZrO 3 (PZ) nanocrystals. .
  • Another method for producing nanocrystals according to the present embodiment is that, when producing nanocrystals of lead titanate PbTiO 3 (PT), an aqueous solution of sodium hydroxide is added to lead (II) acetate trihydrate. And a step of performing heat synthesis using a solution in which a water-soluble titanium complex aqueous solution, an amine compound, and an organic carboxylic acid are mixed. By performing this step, it is possible to stably produce a lead titanate PbTiO 3 (PT) nanocrystal having at least one of the (100) plane, the (010) plane, and the (001) plane as a facet. it can.
  • a compound that dissolves in water, removes a ligand from a titanium atom, and forms a bond between a titanium atom and an oxygen atom can be used.
  • examples of such compounds include complexes of a water-soluble titanium complex with a hydroxycarboxylic acid as a ligand.
  • a complex having a hydroxycarboxylic acid as a ligand is a water-soluble complex that is easily soluble in water.
  • water-soluble titanium complex include titanium bis (ammonium lactate) dihydroxide (hereinafter referred to as “TALH”) in which the ligand is lactic acid, and the ligand is glycolic acid (HOCH 2 COOH).
  • TALH can be preferably used as the water-soluble titanium complex.
  • TALH is a precursor of an oxide containing titanium that is soluble in water, and the reaction of forming an oxide using TALH proceeds under milder conditions than other methods. Further, since TALH is soluble in water, the reaction can be performed in an aqueous solution.
  • a water-soluble titanium complex whose ligand is a hydroxycarboxylic acid, a nanocrystal represented by the general formula Pb (Zr, Ti) O 3 having a controlled nanometer-sized hexahedral structure is obtained. Can be synthesized.
  • the water-soluble zirconium complex a compound that dissolves in water, removes a ligand from the zirconium atom, and forms a bond between the zirconium atom and the oxygen atom can be used.
  • the ligand of the water-soluble zirconium complex is hydroxycarboxylic acid.
  • water-soluble zirconium complex include zirconium lactate ammonium salt.
  • a zirconium lactate ammonium salt (Zr (OH) [(OCH (CH 3 ) COO-] 3 (NH 4 + ) 3 ) can be preferably used as the water-soluble zirconium complex.
  • Chix ZC-300 (trade name: Matsumoto Fine Chemical Co., Ltd.)
  • the ligand has a controlled nanometer-sized hexahedral structure.
  • Nanocrystals represented by the general formula Pb (Zr, Ti) O 3 can be synthesized.
  • a compound in which an unshared electron pair of a nitrogen atom can contribute to the reaction can be used.
  • Such compounds include, for example, tert-butylamine or n-butylamine, and it is particularly preferable to use tert-butylamine.
  • the organic carboxylic acid used in the present invention may be coordinated to the (100) plane, (010) plane or (001) plane of the nanocrystal during the synthesis of the nanocrystal to form the (100) plane or (010) plane of the nanocrystal.
  • a compound that can suppress the crystal growth of the (001) plane or the (001) plane can be used.
  • Oleic acid may be mentioned as such a compound, but a carboxylic acid having a long carbon chain such as decanoic acid (capric acid) CH 3 (CH 2 ) 8 COOH may be used even if it does not contain a double bond. be able to.
  • the amine compound is represented by a general formula Pb (Zr, Ti) O 3 having a controlled hexahedral structure in which tert-butylamine is used and the organic carboxylic acid is oleic acid.
  • Nanocrystals can be synthesized.
  • the pH of the reaction solution is adjusted by adding an aqueous solution of sodium hydroxide.
  • concentration of the aqueous sodium hydroxide solution to be added is determined so as to be 1 mol / L or more and 10 mol / L or less, preferably 4 mol / L or more and 8 mol / L or less, and the concentration is 5 mol / L or more and 7 mol / L or less. More preferably, it is not more than 0.5 mol / L.
  • an aqueous solution of sodium hydroxide (NaOH) is added as a pH adjuster.
  • Ammonia which is often used as a pH adjuster in hydrothermal synthesis, is unlikely to have sufficient strong base conditions to facilitate synthesis (although adding ammonia to the pH 14 condition will not result in a stronger base).
  • sodium hydroxide (NaOH) as a pH adjuster, the reaction solution becomes a sufficiently strong base condition, and the synthesis of the nanocrystal represented by the general formula Pb (Zr, Ti) O 3 is performed. Easy to go.
  • a sodium hydroxide aqueous solution and a precursor solution starting from a lead (II) acetate trihydrate, a water-soluble titanium complex aqueous solution and a water-soluble zirconium complex aqueous solution are used as starting materials.
  • concentration of sodium hydroxide to be mixed is 1 mol / L or more and 10 mol / L or less in a solution in which an organic carboxylic acid (an amine compound is further added as necessary)
  • the synthesis reaction can sufficiently proceed, In addition, aggregation of nanocrystals can be suppressed.
  • the number of moles of the amine compound per mole of lead is preferably 0 or more and 120 or less, more preferably 0 or more and 90 or less. Further, in the solution of the present invention, it is preferable that the number of moles of the organic carboxylic acid is 1 or more and 30 or less with respect to 1 mole of lead.
  • the heating of the reaction solution of this embodiment is preferably performed at a temperature of 140 ° C. or more and 290 ° C. or less, more preferably 170 ° C. or more and 270 ° C. or less, and a temperature of 200 ° C. or more and 250 or less. More preferably, it is performed.
  • the synthesis reaction proceeds sufficiently, and the organic carboxylic acid coordinated to the nanocrystal surface during the reaction is eliminated or the organic carboxylic acid is separated in the reaction solution. By avoiding this, it becomes easier to obtain nanocrystals having a controlled hexahedral structure.
  • the heating of the reaction solution of the present invention is preferably carried out for 1 hour to 80 hours, more preferably for 48 hours to 72 hours.
  • the heating time is less than 1 hour, the synthesis reaction can proceed sufficiently. Further, even if the heating time exceeds 80 hours, the shape of the nanocrystals does not change so much, so it is considered that no further heating is necessary.
  • the heating is performed at a temperature of 140 ° C. or more and 290 ° C. or less and for 1 hour or more and 80 hours or less, so that the synthesis reaction can sufficiently proceed and wasteful A nanocrystal having a controlled hexahedral structure can be obtained without performing any appropriate heating.
  • the solution is centrifuged to collect a precipitate.
  • nanocrystal manufacturing method of the present embodiment by collecting the precipitate by centrifuging the solution after synthesis, unnecessary small crystals and the like are removed, and a nanocrystal having a controlled hexahedral structure is obtained. Obtainable.
  • the electronic device of the present embodiment has the thin film including the nanocrystal according to the above-described embodiment.
  • This electronic device is a known electronic device that utilizes the characteristics of a ferroelectric or antiferroelectric. Examples of the electronic device include a memory device, a sensor, and an actuator.
  • the thin film can be manufactured using the method disclosed in Patent Document 4. That is, the thin film including the nanocrystals in the above-described embodiment can be specifically produced by a method having a mixing step and an arrangement step. Mixing process, Pb (Zr, Ti) a nanocrystal and a non-polar solvent of the present invention represented by O 3 were mixed in a container, Pb (Zr, Ti) nanocrystals of the present invention represented by O 3 This is a step of obtaining a dispersion containing: The arranging step is a step in which the substrate is immersed in the dispersion obtained in the mixing step, and is then lifted up to apply the solution using surface tension, thereby arranging the nanocrystals on the substrate.
  • the piezoelectric element of the present embodiment includes the thin film containing the nanocrystal described in the above embodiment, and a pair of electrodes provided so as to sandwich the thin film.
  • the electrode is formed of a material having conductivity, such as Pt, Ir, and Ru, and which does not react with the ferroelectric film.
  • a 5 mol / L aqueous solution of sodium hydroxide, tert-butylamine and oleic acid were added to prepare a reaction solution.
  • the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was adjusted to be 1: 12: 12: 12.
  • the solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
  • Example 1 The nanocrystals of Example 1 were observed using a scanning electron microscope (JEOL, JSM-6335FM, 10 kV, manufactured by JEOL Ltd.) and a transmission electron microscope (Tecnai @ Osiris, 200 kV, manufactured by FEI), and energy dispersive X-ray fluorescence. Analysis was performed by an analyzer (EDXRF) (EDX-8000, Shimadzu Corporation) and energy dispersive X-ray analysis (EDX) as an accessory device of a transmission electron microscope (TecnaiOsiris, 200 kV, manufactured by FEI). The crystal phase was identified using an X-ray diffractometer (SmartLab, 40 kV / 30 mA, manufactured by Rigaku Corporation).
  • Samples for identification of nanocrystals were prepared by using a colloidal solution obtained by re-dispersing powder recovered by centrifugation in ethanol at room temperature and drying it on a silicon wafer substrate. After irradiating the sample with ultraviolet light for 2 hours, the sample was kept at 200 ° C. for 1.5 hours in an incubator to clean the surface. The same applies to various samples for identification of nanocrystals of other examples.
  • FIG. 1 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing nanocrystals of lead zirconate titanate prepared in Example 1 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown. From the SEM image, in Example 1, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
  • FIG. 2 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 1. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 1 had a perovskite structure with a space group of P4 mm.
  • FIG. 3 shows a high magnification TEM image of the lead zirconate titanate nanocrystals prepared in Example 1.
  • a dispersion containing lead zirconate titanate nanocrystals was dropped on a TEM grid (substrate) arranged on a filter paper, and the solvent in the dropped dispersion was absorbed by the filter paper and removed.
  • the high magnification TEM image shown in FIG. 3 two nanocrystals can be observed, and in the TEM image of the right nanocrystal showing a large range, the presence of two orthogonal facets can be confirmed.
  • lead titanate zirconate nano crystal 1 shown in FIG. 3 has a facet A 1 and facet A 2.
  • a step structure can also be observed in the high-magnification TEM image shown in FIG.
  • FIG. 4A and 4B are a TEM image and an electron diffraction spot image thereof, respectively.
  • the nanocrystal shown in FIG. 4A has a partially sheet-like shape and a partially hexagonal shape, and has a step on the side surface of the sheet-like portion.
  • the plane spacing of the (100) plane in FIG. 4B was 0.396 nm and 0.397 nm. Further, according to TEM-EDX, the composition ratio of the obtained nanocrystals was 1: 0.13: 0.70 for Pb: Zr: Ti.
  • FIG. 4C is a schematic perspective view (not a schematic view corresponding to the nanocrystal shown in FIG. 4A) for explaining characteristics of typical nanocrystals of the present invention.
  • the nanocrystal shown in FIG. 4C has a shape in which a portion having a substantially hexahedral shape (substantially hexahedral portion) is placed on a sheet-shaped portion (sheet-shaped portion). It has a step structure.
  • the flat surface indicates any of the facets (100), (010), and (001).
  • Example 2 Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted such that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 12: 15. Lead acid nanocrystals were synthesized.
  • FIG. 5 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing lead zirconate titanate nanocrystals prepared in Example 2 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown. From the SEM image, in Example 2, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
  • FIG. 6 shows a powder XRD pattern of the lead zirconate titanate nanocrystals produced in Example 2. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 2 had a perovskite structure with a space group of P4 mm.
  • Example 3 Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted so that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 0: 15. Lead acid nanocrystals were synthesized.
  • Example 3 is a case where no amine compound was used.
  • FIG. 7 shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 3 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
  • the nanocrystal located substantially at the center is a sheet-shaped nanocrystal as shown on the right side of the SEM image in FIG. Since the thickness of the nanocrystal is 16 nm and the largest size in the plane spreading direction is about 80 nm, the ratio of the largest size in the plane spreading direction to the size in the thickness direction is 5: 1. It is about.
  • Example 3 nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
  • FIG. 8 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 3. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 3 had a perovskite structure with a space group of P4 mm.
  • Example 4 Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted so that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 36: 15. Lead acid nanocrystals were synthesized.
  • FIG. 9A shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 4 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown. From the SEM image, in Example 4, nanocrystals having a size of 1 nm or more and 100 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary positions, the nanocrystals having a size of 1 nm or more and 30 nm or less were 70% or more.
  • FIG. 10 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 4. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 4 had a perovskite structure with a space group of P4 mm.
  • a 5 mol / L aqueous solution of sodium hydroxide, tert-butylamine and oleic acid were added to prepare a reaction solution.
  • the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was adjusted to be 1: 12: 12: 15.
  • the solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
  • FIG. 11A shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 5 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
  • the diagram shown on the right side of the SEM image in FIG. 11A shows a part of the side surface of the sheet portion of the nanocrystal located at the lower center in FIG. 11A, and shows two steps. did.
  • the nanocrystal has a partially sheet-like shape and a partially hexahedral shape, and has a step on the side surface of the sheet-like portion.
  • FIG. 11B is a perspective view schematically showing an outline of an example of the sheet-like nanocrystal 1C.
  • the sheet-like nanocrystal 1C has a plurality of step structures 21 and facets on a side surface 20A.
  • the nanocrystal 1C shown in FIG. 11B shows facets A 8 , A 9 , A 10 , and A 11 that are part of the facet.
  • FIG. 12 shows a powder XRD pattern of the lead zirconate titanate nanocrystals produced in Example 5. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 5 had a perovskite structure with a space group of P4 mm.
  • the molar ratio of lead (Pb), tert-butylamine and oleic acid was adjusted to be 1:12:12.
  • the solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
  • FIG. 13 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing nanocrystals of lead zirconate titanate prepared in Example 6 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown. From the SEM image, in Example 6, nanocrystals having a size of 1 nm or more and 800 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary positions, the nanocrystals of 1 nm or more and 500 nm or less 70% or more.
  • FIG. 14 shows a powder XRD pattern of the lead titanate nanocrystals produced in Example 6. From the obtained XRD pattern, it was found that the lead titanate nanocrystals produced in Example 6 had a perovskite structure with a space group of P4 mm.
  • PZT is a material that is applied in a wide range of fields such as memory devices, sensors and actuators. Since a nano-sized single crystal exhibits characteristics different from those of a bulk, it is expected that the characteristics are improved by the interaction at the crystal interface or the like by integrating the crystal orientation and three-dimensionally. By combining the nanocrystal of the present invention with the film formation / integration technology of Patent Document 4, it is expected to produce a non-volatile memory element having excellent characteristics or a piezoelectric device element such as an energy harvester.
  • Embodiment 7 A PZT film containing lead zirconate titanate nanocrystals was prepared according to the following procedure. First, the powder of lead zirconate titanate obtained in Example 3 and toluene (a non-polar solvent) were placed in a container, and the container was subjected to ultrasonic waves for 10 minutes to promote dispersion of crystals.
  • a Pt / TiO x / SiO 2 / Si substrate is immersed in a lead titanate zirconate dispersion, pulled up at a speed of 10 nm / sec, and dried to form a titanic acid on the Pt / TiO x / SiO 2 / Si substrate.
  • a sample on which a PZT film containing lead zirconate nanocrystals was formed was obtained.
  • FIG. 15 shows an SEM image of the surface of the obtained sample.
  • FIG. 16 shows a SEM image of a wider range than the SEM image of FIG. From the SEM image, it was found that the lead zirconate titanate nanocrystals were arranged, and a thin film having no unevenness and no holes was formed.
  • FIG. 17 shows an XRD pattern of this sample.
  • FIG. 17 also shows the XRD pattern of the Pt / TiO x / SiO 2 / Si substrate.
  • XRD pattern of the sample a strong peak of the (001) plane of the lead zirconate titanate nanocrystals was confirmed as compared with the powder XRD pattern of FIG. 3, indicating that the sample was preferentially oriented at (001).
  • FIG. 18 shows a d33 -PFM- V curve measured by using a piezoelectric response microscope after heat-treating the sample at 600 ° C. A piezoelectric response was obtained with the application of the voltage, and the piezoelectricity was confirmed. In addition, since the hysteresis characteristics were obtained, it was suggested that they exhibited ferroelectricity.
  • PZT is a material that is applied in a wide range of fields such as memory devices, sensors and actuators. Since a nano-sized single crystal exhibits characteristics different from those of a bulk, it is expected that the characteristics are improved by the interaction at the crystal interface or the like by integrating the crystal orientation and three-dimensionally. By combining the nanocrystal of the present invention with the film formation / integration technology of Patent Document 4, it is expected to produce a non-volatile memory element having excellent characteristics or a piezoelectric device element such as an energy harvester.
  • the nanocrystal of the present invention can be used for nonvolatile memories, sensors, actuators, piezoelectric devices, and the like.

Abstract

This nanocrystal: is a monocrystal represented by Pb(Zr,Ti)O3; has at least one of a (100) plane, a (010) plane and a (001) plane as a facet; and has a size of 1-1,000 nm.

Description

ナノ結晶及びその製造方法、並びにナノ結晶を用いた電子デバイス及び圧電素子Nanocrystal and its manufacturing method, and electronic device and piezoelectric element using nanocrystal
　本発明は、ナノ結晶及びその製造方法、並びにナノ結晶を用いた電子デバイス及び圧電素子に関するものである。
　本出願は、２０１８年６月２９日に日本に出願された特願２０１８－１２４７５４号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a nanocrystal and a method for producing the same, and an electronic device and a piezoelectric element using the nanocrystal.
This application claims priority based on Japanese Patent Application No. 2018-124754 filed on June 29, 2018, the contents of which are incorporated herein by reference.
　金属酸化物であるチタン酸ジルコン酸鉛Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（０＜ｘ＜１）（ＰＺＴ）は、チタン酸鉛ＰｂＴｉＯ３（ＰＴ）およびジルコン酸鉛ＰｂＺｒＯ３（ＰＺ）の混晶であり、ペロブスカイト型の結晶構造を有する強誘電体である。また、優れた圧電効果を示す圧電体としても知られている。こうしたチタン酸ジルコン酸鉛、チタン酸鉛、ジルコン酸鉛のナノ結晶は、サイズに起因した特徴的な物性を発現しうる新規材料としての応用が期待されている。 Lead zirconate titanate Pb (Zr x Ti 1-x ) O 3 (0 <x <1) (PZT) which is a metal oxide is composed of lead titanate PbTiO 3 (PT) and lead zirconate PbZrO 3 (PZ). And is a ferroelectric having a perovskite crystal structure. Further, it is also known as a piezoelectric material exhibiting an excellent piezoelectric effect. Such nanocrystals of lead zirconate titanate, lead titanate, and lead zirconate are expected to be applied as novel materials capable of expressing characteristic physical properties due to size.
　チタン酸ジルコン酸鉛（ＰＺＴ）薄膜は、ゾルゲル法、有機金属熱分解法、有機金属気相成長法など様々な手法で製膜されている。しかし、ＰＺＴ薄膜の結晶化にはおよそ６００℃以上の焼成温度が必要であるため、ＰＺＴ膜／Ｓｉ基板界面における拡散あるいは反応等、高温処理を経ることによるデバイス劣化が問題である。また、ＰＺＴ中に含まれる鉛は揮発性物質であり、出発原料と作製した膜との組成ずれが起こり易く組成制御が困難であるため、従来のような高温焼成を必要としない水熱合成法によるＰＺＴ膜の作製が注目されている。 鉛 Lead zirconate titanate (PZT) thin films are formed by various methods such as a sol-gel method, an organic metal thermal decomposition method, and an organic metal vapor phase epitaxy method. However, since the crystallization temperature of the PZT thin film requires a firing temperature of about 600 ° C. or more, device degradation due to high-temperature processing such as diffusion or reaction at the PZT film / Si substrate interface is a problem. In addition, lead contained in PZT is a volatile substance, and compositional deviation between a starting material and a formed film is apt to occur and composition control is difficult. The production of PZT films by the method has attracted attention.
　水熱合成法によるＰＺＴ膜の作製では、チタン原料とするチタン基板と、鉛およびジルコニウム原料溶液とを合成容器内で反応させる手法（特許文献１参照）が報告されている。しかし、この手法では、チタン基板と溶液の反応により、反応結晶核生成過程としてＰＺ／ＰＴ結晶核が生成し、その後結晶核成長過程でＰＺ膜上にＰＺＴ膜が形成される二段階プロセスであるため、ＰＺＴ／ＰＺ／ＰＴの多層構造が形成されること、および核生成および核成長過程の制御が困難である。そこで、チタン基板と鉛、ジルコニウムおよびチタン原料溶液を反応させる単一プロセスによりＰＺＴ膜を得る手法、あるいはチタン基板を用いず、鉛、ジルコニウムおよびチタン原料溶液を合成容器内で反応させてＰＺＴ粒子を得る手法（特許文献２参照）が開発された。このように、水熱合成法を用いたＰＺＴ膜の作製あるいはＰＺＴ粒子を合成する技術は既に報告されている。 In the production of a PZT film by a hydrothermal synthesis method, a method has been reported in which a titanium substrate as a titanium raw material is reacted with a lead and zirconium raw material solution in a synthesis vessel (see Patent Document 1). However, this method is a two-step process in which a PZ / PT crystal nucleus is generated as a reaction crystal nucleus generation process by a reaction between a titanium substrate and a solution, and then a PZT film is formed on the PZ film in a crystal nucleus growth process. Therefore, it is difficult to form a multilayer structure of PZT / PZ / PT and to control nucleation and nucleus growth processes. Therefore, a method of obtaining a PZT film by a single process of reacting a titanium substrate with a lead, zirconium and titanium raw material solution, or reacting a lead, zirconium and titanium raw material solution in a synthesis vessel without using a titanium substrate to form PZT particles A technique for obtaining (see Patent Document 2) has been developed. As described above, a technique of producing a PZT film using a hydrothermal synthesis method or synthesizing PZT particles has been already reported.
特開平６－２１１５２３号公報JP-A-6-215523 特開平１１－１１６３９５号公報JP-A-11-116395 国際公開第２０１４／１３２７２０号International Publication No. WO 2014/132720 国際公開第２０１６／０６００４２号International Publication No. WO 2016/060042
　一方、形状を制御したナノサイズの単結晶はバルクとは異なる特性を発現することが知られているため近年注目されている。サイズが０．５μｍから１０μｍすなわちミクロンサイズで、かつ形状が立方体、直方体および切頂八面体のずれかであることを特徴とするＰＺＴ粒子およびその製造方法に関しては既に報告されている（特許文献３参照）。
　しかしながら、その結晶方位については報告されておらず、ナノサイズのＰＺＴ結晶の合成、形態制御および結晶構造に関しては報告例がほとんどない。
　また、サイズに起因した特徴的な物性の発現が期待されるのはミクロンサイズよりも小さな、例えばサイズが数十ｎｍから数百ｎｍ程度であるから、このサイズのチタン酸ジルコン酸鉛、チタン酸鉛、ジルコン酸鉛のナノ結晶を安定して製造することが求められている。 On the other hand, nano-sized single crystals with controlled shapes are known in recent years because they are known to exhibit characteristics different from those of bulk. A PZT particle having a size of 0.5 μm to 10 μm, that is, a micron size, and having a shape of a cube, a rectangular parallelepiped, or a truncated octahedron, and a method for producing the same have already been reported (Patent Document 3). reference).
However, the crystal orientation is not reported, and there are few reports on the synthesis, morphology control, and crystal structure of nano-sized PZT crystals.
Also, it is expected that the development of characteristic physical properties due to the size is smaller than the micron size, for example, the size is about several tens nm to several hundreds nm. Therefore, lead zirconate titanate and titanate of this size are used. There is a demand for stable production of lead and lead zirconate nanocrystals.
　本発明は、上述した状況に鑑みてなされたものであって、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有するナノ結晶及びその製造方法、並びにナノ結晶を用いた電子デバイス及び圧電素子を提供することを目的とする。 The present invention has been made in view of the above situation, and has been made in view of the above circumstances, and has a nanocrystal having at least one of a (100) plane, a (010) plane, and a (001) plane as a facet, a method for producing the same, and a nanocrystal. It is an object to provide an electronic device and a piezoelectric element using a crystal.
　本発明者は、鋭意検討を進めた結果、（１００）面、（０１０）面あるいは（００１）面のファセットを有し、高結晶性のチタン酸ジルコン酸鉛、チタン酸鉛、ジルコン酸鉛のナノ結晶の合成に成功し、本発明に想到した。 As a result of diligent studies, the present inventor has a (100) face, a (010) face, or a (001) facet, and has a high crystallinity of lead zirconate titanate, lead titanate, and lead zirconate. Successful synthesis of nanocrystals led to the present invention.
　本発明は、上記課題を解決するため、以下の手段を提供する。 The present invention provides the following means in order to solve the above problems.
（１）本発明の第１の態様に係るナノ結晶は、Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表される単結晶であり、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有すると共に、サイズが１ｎｍ以上１０００ｎｍ以下である。 (1) The nanocrystal according to the first embodiment of the present invention is a single crystal represented by Pb (Zr, Ti) O 3 and has at least one of a (100) plane, a (010) plane, and a (001) plane. One of them is a facet, and the size is 1 nm or more and 1000 nm or less.
（２）上記態様において、結晶の形状は、シート状形状、略六面体形状、又は、部分的にシート状形状でかつ部分的に略六面体形状、のいずれかであってもよい。 (2) In the above aspect, the shape of the crystal may be any of a sheet-like shape, a substantially hexahedral shape, or a partially sheet-like and partially substantially hexahedral shape.
（３）上記態様において、前記結晶の形状がシート状形状、又は、部分的にシート状形状でかつ部分的に略六面体形状である場合に、シートの側面に段差を有してもよい。 (3) In the above aspect, when the shape of the crystal is a sheet-like shape, or is partially sheet-like and partially substantially hexahedral, a step may be provided on a side surface of the sheet.
（４）本発明の第２の態様に係るナノ結晶の製造方法は、酢酸鉛（II）三水和物、水溶性チタン錯体水溶液および水溶性ジルコニウム錯体水溶液を出発原料とする前駆体溶液に、水酸化ナトリウム水溶液および有機カルボン酸を混合した溶液を用いて加熱合成する工程を含む。 (4) The method for producing a nanocrystal according to the second aspect of the present invention comprises the steps of: preparing a precursor solution using lead (II) acetate trihydrate, a water-soluble titanium complex aqueous solution and a water-soluble zirconium complex aqueous solution as starting materials, The method includes a step of performing heat synthesis using a mixed solution of an aqueous solution of sodium hydroxide and an organic carboxylic acid.
（５）上記態様において、前記水溶性ジルコニウム錯体の配位子がヒドロキシカルボン酸であってもよい。 (5) In the above aspect, the ligand of the water-soluble zirconium complex may be a hydroxycarboxylic acid.
（６）本発明の第３の態様に係るナノ結晶の製造方法は、酢酸鉛（II）三水和物に水酸化ナトリウム水溶液を添加した後、水溶性チタン錯体水溶液、アミン化合物、有機カルボン酸を混合した溶液を用いて加熱合成する工程を含む。 (6) The method for producing nanocrystals according to the third aspect of the present invention comprises the steps of: adding an aqueous sodium hydroxide solution to lead (II) acetate trihydrate, and then adding an aqueous solution of a water-soluble titanium complex, an amine compound, and an organic carboxylic acid. And heat-synthesizing using a solution in which is mixed.
（７）上記態様において、前記水溶性チタン錯体の配位子がヒドロキシカルボン酸であってもよい。 (7) In the above aspect, the ligand of the water-soluble titanium complex may be a hydroxycarboxylic acid.
（８）上記態様において、前記有機カルボン酸がオレイン酸であってもよい。 (8) In the above aspect, the organic carboxylic acid may be oleic acid.
（９）上記態様において、前記水酸化ナトリウム水溶液の濃度が１ｍｏｌ／Ｌ以上１０ｍｏｌ／Ｌ以下であってもよい。 (9) In the above aspect, the concentration of the aqueous sodium hydroxide solution may be 1 mol / L or more and 10 mol / L or less.
（１０）上記態様において、前記溶液において鉛１モルに対する有機カルボン酸のモル数が１以上３０以下であってもよい。 (10) In the above aspect, the number of moles of the organic carboxylic acid per mole of lead in the solution may be from 1 to 30.
（１１）上記態様において、前記加熱を、１４０℃以上２９０℃以下の温度で実施してもよい。 (11) In the above aspect, the heating may be performed at a temperature of 140 ° C or more and 290 ° C or less.
（１２）上記態様にいて、前記加熱を、１時間以上８０時間以下の時間で実施してもよい。 (12) In the above aspect, the heating may be performed for 1 hour or more and 80 hours or less.
（１３）上記態様において、前記加熱を行った後の溶液を遠心分離する工程を有してもよい。 (13) In the above aspect, a step of centrifuging the solution after the heating may be included.
（１４）本発明の第４の態様に係る電子デバイスは、上記態様に係るナノ結晶を含む薄膜を有する。 (14) An electronic device according to a fourth aspect of the present invention includes the thin film including the nanocrystal according to the above aspect.
（１５）本発明の第５の態様に係る圧電素子は、上記態様に係るナノ結晶を含む薄膜と、該薄膜を挟むように設けられた一対の電極とを備える。 (15) A piezoelectric element according to a fifth aspect of the present invention includes the thin film containing the nanocrystal according to the above aspect, and a pair of electrodes provided so as to sandwich the thin film.
　本発明のナノ結晶によれば、（１００）面、（０１０）面又は（００１）面の少なくともいずれか一つをファセットとして有し、バルクとは異なる特性が期待されるナノ結晶を提供できる。 According to the nanocrystal of the present invention, it is possible to provide a nanocrystal that has at least one of the (100) plane, the (010) plane, and the (001) plane as a facet and is expected to have properties different from those of a bulk.
実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。3 is an SEM image of the surface of a sample produced by drop-drying the dispersion containing lead zirconate titanate nanocrystals produced in Example 1 on a silicon wafer substrate at room temperature. 実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶を含むサンプルの粉末Ｘ線回折（ＸＲＤ）パターンである。3 is a powder X-ray diffraction (XRD) pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 1. 実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶の高倍率のＴＥＭ像である。2 is a high-magnification TEM image of the lead zirconate titanate nanocrystals produced in Example 1. 実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶のＴＥＭ像である。3 is a TEM image of lead zirconate titanate nanocrystals produced in Example 1. 実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶の電子回折パターンである。3 is an electron diffraction pattern of a lead zirconate titanate nanocrystal prepared in Example 1. 本発明の典型的なナノ結晶が有する特徴を説明するために模式的に示した斜視図である。FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention. 実施例２で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。9 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing nanocrystals of lead zirconate titanate manufactured in Example 2 on a silicon wafer substrate at room temperature. 実施例２で作製したチタン酸ジルコン酸鉛ナノ結晶を含むサンプルの粉末ＸＲＤパターンである。5 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 2. 実施例３で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。9 is an SEM image of the surface of a sample manufactured by drop drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 3 on a silicon wafer substrate at room temperature. 実施例３で作製したチタン酸ジルコン酸鉛ナノ結晶を含むサンプルの粉末ＸＲＤパターンである。9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 3. 実施例４で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。9 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing nanocrystals of lead zirconate titanate manufactured in Example 4 on a silicon wafer substrate at room temperature. 本発明の典型的なナノ結晶が有する特徴を説明するために模式的に示した斜視図である。FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention. 実施例４で作製したチタン酸ジルコン酸鉛ナノ結晶を含むサンプルの粉末ＸＲＤパターンである。9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 4. 実施例５で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。11 is an SEM image of the surface of a sample prepared by drop drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 5 on a silicon wafer substrate at room temperature. 本発明の典型的なナノ結晶が有する特徴を説明するために模式的に示した斜視図である。FIG. 3 is a perspective view schematically illustrating a characteristic of a typical nanocrystal of the present invention. 実施例５で作製したチタン酸ジルコン酸鉛ナノ結晶を含むサンプルの粉末ＸＲＤパターンである。9 is a powder XRD pattern of a sample containing lead zirconate titanate nanocrystals prepared in Example 5. 実施例６で作製したチタン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像である。11 is an SEM image of the surface of a sample manufactured by drop-drying a dispersion containing lead titanate nanocrystals manufactured in Example 6 on a silicon wafer substrate at room temperature. 実施例６で作製したチタン酸鉛ナノ結晶を含むサンプルの粉末ＸＲＤパターンである。9 is a powder XRD pattern of a sample containing lead titanate nanocrystals prepared in Example 6. 実施例７で作製したチタン酸ジルコン酸鉛ナノ結晶膜のサンプル表面のＳＥＭ像である。11 is an SEM image of a sample surface of a lead zirconate titanate nanocrystal film produced in Example 7. 実施例７で作製したチタン酸ジルコン酸鉛ナノ結晶膜のサンプル表面のＳＥＭ像である。11 is an SEM image of a sample surface of a lead zirconate titanate nanocrystal film produced in Example 7. 実施例７で作製したチタン酸ジルコン酸鉛ナノ結晶膜のサンプルのＸＲＤパターンである。9 is an XRD pattern of a sample of a lead zirconate titanate nanocrystal film prepared in Example 7. 実施例７で作製したチタン酸ジルコン酸鉛ナノ結晶膜のサンプルについて、６００℃で熱処理を行った後、圧電応答顕微鏡を用いて測定した圧電定数?印加電圧（ｄ３３－ＰＦＭ－Ｖ）曲線である。The sample of the lead zirconate titanate nanocrystal film prepared in Example 7 was subjected to a heat treatment at 600 ° C., and then measured by using a piezoelectric response microscope to obtain a piezoelectric constant-applied voltage (d33 -PFM- V) curve. is there.
　以下、図面を参照して、本発明の一実施形態のナノ結晶及びその製造方法並びにナノ結晶を用いた圧電素子の好ましい例について説明する。なお、以下に示す各実施形態は、発明の趣旨をより良く理解させるために具体的に説明するものであり、特に指定のない限り、本発明を限定するものではない。すなわち、本発明は、以下に示す実施形態のみに限定されるものではなく、その効果を奏する範囲で適宜変更して実施することが可能である。例えば、本発明の主旨を逸脱しない範囲で、長さ、位置、形状、数、量。および材料等について、省略、追加、置換、その他の変更が可能である。 Hereinafter, with reference to the drawings, a description will be given of preferred examples of a nanocrystal and a method of manufacturing the same according to an embodiment of the present invention, and a piezoelectric element using the nanocrystal. Each embodiment described below is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified. That is, the present invention is not limited to only the embodiments described below, and can be implemented with appropriate modifications as long as the effects are obtained. For example, length, position, shape, number, and quantity without departing from the gist of the present invention. Omissions, additions, substitutions, and other changes can be made to materials and materials.
（ナノ結晶）
　本発明のナノ結晶は、Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表される単結晶であり、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有する。すなわち、本実施形態のナノ結晶は平坦面である（１００）面、（０１０）面、（００１）面の少なくともいずれか１つをファセットとして有する。また、本実施形態のナノ結晶はサイズが１ｎｍ以上１０００ｎｍ以下であり、好ましくは３ｎｍ以上９００ｎｍ以下であり、より好ましくは５ｎｍ以上７５０ｎｍ以下である。
　本明細書において、「Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３」とは、Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（０≦ｘ≦１）の場合の他、組成比がＰｂ：（Ｚｒ＋Ｔｉ）＝１：１ではない場合も含む。 (Nanocrystal)
The nanocrystal of the present invention is a single crystal represented by Pb (Zr, Ti) O 3 and has at least one of a (100) plane, a (010) plane, and a (001) plane as a facet. That is, the nanocrystal of the present embodiment has at least one of the (100) plane, the (010) plane, and the (001) plane, which are flat planes, as facets. The size of the nanocrystal of the present embodiment is 1 nm or more and 1000 nm or less, preferably 3 nm or more and 900 nm or less, and more preferably 5 nm or more and 750 nm or less.
In the present specification, “Pb (Zr, Ti) O 3 ” means Pb (Zr x Ti 1-X ) O 3 (0 ≦ x ≦ 1) and also has a composition ratio of Pb: (Zr + Ti) = This includes cases where the ratio is not 1: 1.
　本実施形態のナノ結晶が一般式Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（０≦ｘ≦１）で表される場合、０＜ｘ＜１のときはチタン酸ジルコン酸鉛（ＰＺＴ）であり、ｘ＝０のときはチタン酸鉛（ＰＴ）であり、ｘ＝１のときはジルコン酸鉛（ＰＺ）である。 When the nanocrystal of the present embodiment is represented by the general formula Pb (Zr x Ti 1-x ) O 3 (0 ≦ x ≦ 1), when 0 <x <1, lead zirconate titanate (PZT) is used. When x = 0, it is lead titanate (PT), and when x = 1, it is lead zirconate (PZ).
　ここで、ＰＺＴは、強誘電体のチタン酸鉛と反強誘電体のジルコン酸鉛の混晶である。ＰＺＴは、室温ではＺｒとＴｉの組成比によって正方晶や菱面体晶などの結晶構造が存在し、ｘ＝０．５２付近に正方晶と菱面体晶とのモルフォトロピック相境界が存在する。ＰＺＴは、ｘ＝０．５２の近傍の組成において最も大きな圧電特性を示す。また、ＰＺＴ結晶構造はペロブスカイト構造を有する。また、チタン酸鉛（ＰＴ）は正方晶であり、ジルコン酸鉛（ＰＺ）は菱面体晶である。 Here, PZT is a mixed crystal of ferroelectric lead titanate and antiferroelectric lead zirconate. At room temperature, PZT has a crystal structure such as tetragonal or rhombohedral depending on the composition ratio of Zr and Ti, and a morphotropic phase boundary between tetragonal and rhombohedral exists near x = 0.52. PZT shows the largest piezoelectric characteristic at a composition near x = 0.52. Further, the PZT crystal structure has a perovskite structure. Lead titanate (PT) is tetragonal, and lead zirconate (PZ) is rhombohedral.
　本発明のナノ結晶は、組成によって、正方晶あるいは略正方晶のペロブスカイト構造か、菱面体晶あるいは略菱面体晶のペロブスカイト構造などを有するものであり、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有するものである。 The nanocrystal of the present invention has a tetragonal or substantially tetragonal perovskite structure, a rhombohedral or substantially rhombohedral perovskite structure, or the like, depending on the composition, and has a (100) plane, a (010) plane, and a (100) plane. 001) as at least one facet.
　本実施形態に係るナノ結晶の形状は、シート状形状、略六面体形状、又は、部分的にシート状形状でかつ部分的に略六面体形状を有する形状であってもよい。
　ここで、シート状形状のナノ結晶とは、面拡がり方向のサイズに比べて厚み方向のサイズが小さいナノ結晶であって、限定するものではないが、目安を言えば、面拡がり方向のサイズのうち最大のサイズと厚み方向のサイズの比が３：１より大きな差がある場合をいう。シート状形状のナノ結晶の面拡がり方向のサイズのうち最大のサイズと厚み方向のサイズの比は、５：１より大きい差があってもよく、１０：１より大きい差があってもよく、２０：１より大きい差があってもよい。
　なお、シート状形状のナノ結晶の例示のために、後述する図７のＳＥＭ像に基づいて典型的なシート状形状のナノ結晶を示した。図７においてほぼ中央に位置するナノ結晶（矢印の延長上に位置するナノ結晶）は、シート状形状のナノ結晶である。シート状形状のナノ結晶は、例えば図７のＳＥＭ像の右方に示したような形状や、図１１Ｂに示したような形状である。本実施形態に記載のナノ結晶は、シート状形状である場合、基板上に集積させた際、配向性を制御しやすい。また本実施形態に記載のナノ結晶はシート状形状である場合、比表面積が大きくナノ結晶とナノ結晶の界面あるいは基材との密着性が高いことや素子の小型化が可能という点で好ましい。 The shape of the nanocrystal according to the present embodiment may be a sheet shape, a substantially hexahedral shape, or a shape having a partially sheet shape and a partially substantially hexahedral shape.
Here, the sheet-shaped nanocrystal is a nanocrystal whose size in the thickness direction is smaller than the size in the surface spreading direction, and is not limited, but as a guide, the size of the surface spreading direction is The case where the ratio between the maximum size and the size in the thickness direction has a difference of more than 3: 1. Among the sizes of the sheet-shaped nanocrystals in the plane spreading direction, the ratio between the maximum size and the size in the thickness direction may have a difference of more than 5: 1 or may have a difference of more than 10: 1, There may be a difference of more than 20: 1.
For the purpose of illustrating the sheet-shaped nanocrystal, a typical sheet-shaped nanocrystal is shown based on an SEM image of FIG. 7 described later. In FIG. 7, the nanocrystal located substantially at the center (the nanocrystal located on the extension of the arrow) is a sheet-shaped nanocrystal. The sheet-shaped nanocrystal has, for example, a shape as shown on the right side of the SEM image in FIG. 7 and a shape as shown in FIG. 11B. When the nanocrystals described in the present embodiment have a sheet-like shape, the orientation can be easily controlled when integrated on a substrate. Further, the nanocrystal described in the present embodiment is preferably in the form of a sheet in that it has a large specific surface area, high adhesion to an interface between the nanocrystal and the nanocrystal or a base material, and downsizing of the element is possible.
　また、部分的にシート状形状でかつ部分的に略六面体形状のナノ結晶の例示のために、図４Ｃに模式的に斜視図を示した。図４Ｃで模式的に示したナノ結晶１Ａは、シート状形状のシート状部２とシート状部１０上に位置する六面体形状の六面体形状部３を有する。ここで、六面体形状部３は、一面がシート状部２に接するため厳密には六面体形状ではなく、略六面体形状であってもよい。図４Ｃで模式的に示したナノ結晶１Ａは、シート状部２の側面２０において後述する段差構造２１を複数有する。段差構造２１を形成する面のうち側面と交わる面と側面との角度は任意の角度とすることができる。図４Ｃには、六面体形状部３を１つ有するナノ結晶１Ａを記載したが、この例に限定されず、ナノ結晶１Ａは任意の数の六面体形状部３を有することができる。 FIG. 4C schematically shows a perspective view of a partially-sheet-shaped and partially hexahedral-shaped nanocrystal. The nanocrystal 1 </ b> A schematically shown in FIG. 4C has a sheet-shaped sheet portion 2 and a hexahedral hexahedral portion 3 located on the sheet portion 10. Here, the hexahedral shape portion 3 may not be strictly a hexahedral shape but may be a substantially hexahedral shape since one surface is in contact with the sheet-like portion 2. The nanocrystal 1A schematically shown in FIG. 4C has a plurality of step structures 21 described later on the side surface 20 of the sheet-like portion 2. The angle between the side surface that intersects the side surface and the side surface among the surfaces forming the step structure 21 can be an arbitrary angle. Although FIG. 4C illustrates the nanocrystal 1A having one hexahedral shape portion 3, the present invention is not limited to this example, and the nanocrystal 1A can have an arbitrary number of hexahedral shape portions 3.
　図４Ｃには、ファセット面の例を一部だけ示す。図４Ｃに示されるＡ３、Ａ４、Ａ５、Ａ６、Ａ７はそれぞれファセット面である。図４Ｃに示すナノ結晶１Ａは（００１）面、（０１０）面、（１００）面のいずれにもファセットを有する。具体的には、Ａ３が（１００）面のファセットであったとすると、Ａ４及びＡ７が（０１０）面のファセットであり、Ａ５及びＡ６が（００１）面のファセットである。すなわち、ナノ結晶１Ａは（１００）面、（０１０）面および（００１）面のいずれもファセットとして有する。本実施形態はこの例に限定されず、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有していればよい。本実施形態のナノ結晶の表面は、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有していれば、複数の平坦面のみからなってもよいし、平坦面と曲面とが組み合わさっていても良い。隣り合う面と面とがつくる角度は鋭角または鈍角であってもよい。
　１つのナノ結晶は、六面体形状、略六面体形状およびシート状形状からなる群から任意に選択される、１つの形状、または２つ以上を組み合わせた形状を、有してよい。各形状のサイズや、縦、横及び厚さの比率などは任意に選択できる。また異なるサイズや異なる比率の各形状が、１つのナノ結晶に含まれていても良い。全て同じサイズであってもよく、同じ形状であっても良い。上記形状は走査電子顕微鏡、透過型電子顕微鏡等を使用して確認しても良い。 FIG. 4C shows only a part of the example of the facet surface. A 3 , A 4 , A 5 , A 6 , and A 7 shown in FIG. 4C are facet planes, respectively. The nanocrystal 1A shown in FIG. 4C has facets on any of the (001), (010), and (100) planes. Specifically, if A 3 is a facet of the (100) plane, A 4 and A 7 are facets of the (010) plane, and A 5 and A 6 are facets of the (001) plane. That is, the nanocrystal 1A has a facet in any of the (100) plane, the (010) plane, and the (001) plane. This embodiment is not limited to this example, and it is sufficient that at least one of the (100) plane, the (010) plane, and the (001) plane is provided as a facet. The surface of the nanocrystal of this embodiment may consist of only a plurality of flat surfaces as long as it has at least one of the (100) plane, the (010) plane and the (001) plane as a facet. Alternatively, a flat surface and a curved surface may be combined. The angle between adjacent surfaces may be acute or obtuse.
One nanocrystal may have one shape or a shape combining two or more arbitrarily selected from the group consisting of a hexahedral shape, a substantially hexahedral shape, and a sheet-like shape. The size of each shape and the ratio of length, width, and thickness can be arbitrarily selected. In addition, different shapes having different sizes and different ratios may be included in one nanocrystal. All may have the same size or the same shape. The above shape may be confirmed using a scanning electron microscope, a transmission electron microscope, or the like.
　本実施形態に係るナノ結晶の形状が略六面体形状である場合、ナノ結晶は、六面体状や略六面体状の結晶だけでなく六面体の頂点が面取りされた不完全な六面体状の結晶であってもよい。すなわち略六面体形状のナノ結晶は、ナノ結晶の合成が十分に進んだ段階のものは六面体状あるいは略六面体状の結晶だけでなく同時に合成される、六面体の頂点が面取りされた不完全な六面体状の結晶をも含む。この六面体の頂点が面取りされた不完全な六面体状の結晶は六面体状の結晶になる途上のものであるが、六面体状や略六面体状のナノ結晶と同様に、バルクとは異なる特性が期待される。
　略六面体形状のナノ結晶は例えば、図９ＡのＳＥＭ像中に多く見られる。略六面体形状のナノ結晶の例示のために、図４Ｃに模式的に斜視図を示した。図９Ｂに略六面体形状のナノ結晶の典型例の斜視図を示した。図９Ｂに示した略六面体形状のナノ結晶は、六面体の少なくとも一つの頂点が面取りされた不完全な六面体状の結晶１Ａである。図９Ｂに示す略六面体形状のナノ結晶１Ｂは、面取り部１０と、ファセットを有する。図９Ｂに示すナノ結晶１Ｂはファセットの一部であるファセットＡ８、Ａ９、Ａ１０、Ａ１１が示されている。 When the shape of the nanocrystal according to the present embodiment is a substantially hexahedral shape, the nanocrystal is not only a hexahedral or substantially hexahedral crystal, but also an incomplete hexahedral crystal in which the vertices of the hexahedron are chamfered. Good. In other words, nanocrystals of approximately hexahedral shape are not only hexahedral or approximately hexahedral crystals that are synthesized at the stage when nanocrystal synthesis is sufficiently advanced, but also incomplete hexahedral shapes in which the vertices of the hexahedron are chamfered. Also includes crystals of The imperfect hexahedral crystal whose apex of the hexahedron is chamfered is in the process of becoming a hexahedral crystal, but similar to hexahedral or nearly hexahedral nanocrystals, it is expected to have different properties from bulk. You.
For example, a substantially hexahedral nanocrystal is often seen in the SEM image of FIG. 9A. FIG. 4C is a perspective view schematically illustrating a nanocrystal having a substantially hexahedral shape. FIG. 9B shows a perspective view of a typical example of a substantially hexahedral nanocrystal. The substantially hexahedral nanocrystal shown in FIG. 9B is an incomplete hexahedral crystal 1A in which at least one vertex of the hexahedron is chamfered. The substantially hexahedral nanocrystal 1B shown in FIG. 9B has a chamfer 10 and a facet. The nanocrystal 1B shown in FIG. 9B shows facets A 8 , A 9 , A 10 , and A 11 which are a part of the facet.
　本実施形態に係るナノ結晶の形状がシート状形状である場合に、そのシート状ナノ結晶は側面に段差を有してもよい。段差の各段はシート状ナノ結晶の厚み方向に延在し、各段がシート状ナノ結晶の外周に沿って並ぶものでもよい。段差の各段は（１００）面、（０１０）面、又は、（００１）面のいずれかの面からなってもよい。
　本実施形態に係るナノ結晶の形状が部分的にシート状形状でかつ部分的に略六面体形状である場合に、ナノ結晶はシート状部２の側面２０に段差２１を有してもよい。段差２０の各段はシート状部２の厚み方向に延在し、各段がシート状部分の外周に沿って並ぶものでもよい。段差２０の各段は（１００）面、（０１０）面、又は、（００１）面のいずれかの面からなってもよい。
　なお、シート状ナノ結晶の側面における段差およびナノ結晶のうちシート状部２の側面２０における段差２１の例示のために、後述する図１１ＡのＳＥＭ像に基づいて典型的な段差を示した。図１１ＡのＳＥＭ像の右方に示した線図は、図１１Ａにおいて中央下側に位置するナノ結晶のシート状部分の側面の一部を象ったものであり、２か所の段差を図示した。 When the shape of the nanocrystal according to the present embodiment is a sheet-like shape, the sheet-like nanocrystal may have a step on a side surface. Each step of the step may extend in the thickness direction of the sheet-like nanocrystal, and each step may be arranged along the outer periphery of the sheet-like nanocrystal. Each step of the step may be composed of any one of the (100) plane, the (010) plane, and the (001) plane.
When the shape of the nanocrystal according to the present embodiment is partially sheet-like and partially substantially hexahedral, the nanocrystal may have a step 21 on the side surface 20 of the sheet-like portion 2. Each step of the step 20 may extend in the thickness direction of the sheet-like portion 2, and each step may be arranged along the outer periphery of the sheet-like portion. Each step of the step 20 may be composed of any one of the (100) plane, the (010) plane, and the (001) plane.
In order to illustrate a step on the side surface of the sheet-like nanocrystal and a step 21 on the side surface 20 of the sheet-like portion 2 of the nanocrystal, a typical step is shown based on a SEM image of FIG. The diagram shown on the right side of the SEM image in FIG. 11A shows a part of the side surface of the sheet portion of the nanocrystal located at the lower center in FIG. 11A, and shows two steps. did.
　本発明のナノ結晶のサイズは、１ｎｍ以上１０００ｎｍ以下である。ナノ結晶のサイズは、好ましくは１ｎｍ以上８００ｎｍ以下であり、より好ましくは１ｎｍ以上５００ｎｍ以下であり、さらに好ましくは１ｎｍ以上２００ｎｍ以下である。また、用途によっては、１ｎｍ以上１００ｎｍ以下であることが好ましい場合もあり、１ｎｍ以上５０ｎｍ以下であることがより好ましい場合もある。例えば、本実施形態に記載のナノ結晶を電子デバイス用途で用いる場合は、１ｎｍ以上１００ｎｍ以下のナノ結晶を用いることで電子デバイスの小型化が可能となる。
　ここで、ナノ結晶のサイズとは、ナノ結晶の電子顕微鏡像（ＳＥＭ像やＴＥＭ像等）の外周において、離間する２点を結んだ距離のうち最も大きい距離（長さ）を意味するものとする。言い換えると、ナノ結晶の電子顕微鏡像（ＳＥＭ像やＴＥＭ像等）においてナノ結晶の２点の最長の長さを意味する。 The size of the nanocrystal of the present invention is 1 nm or more and 1000 nm or less. The size of the nanocrystal is preferably from 1 nm to 800 nm, more preferably from 1 nm to 500 nm, and still more preferably from 1 nm to 200 nm. Further, depending on the use, it is preferable that the thickness be 1 nm or more and 100 nm or less, and it is more preferable that the thickness be 1 nm or more and 50 nm or less. For example, when the nanocrystal described in this embodiment is used for an electronic device, the size of the electronic device can be reduced by using a nanocrystal having a size of 1 nm to 100 nm.
Here, the size of the nanocrystal means the largest distance (length) of the distance connecting two separated points on the outer periphery of the electron microscope image (SEM image, TEM image, etc.) of the nanocrystal. I do. In other words, it means the longest length of two points of the nanocrystal in an electron microscope image (SEM image, TEM image, etc.) of the nanocrystal.
（ナノ結晶の製造方法）
　本実施形態に係るナノ結晶の製造方法は、チタン酸ジルコン酸鉛Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（０＜ｘ＜１）（ＰＺＴ）のナノ結晶を製造する場合、酢酸鉛（II）三水和物、水溶性チタン錯体水溶液および水溶性ジルコニウム錯体水溶液を出発原料とする前駆体溶液に、水酸化ナトリウム水溶液および有機カルボン酸を混合した溶液を用いて加熱合成する工程を含む。当該構成により、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有するナノ結晶を安定して製造することができる。
　また、前駆体溶液に、水酸化ナトリウム水溶液および有機カルボン酸の他に、アミン化合物を混合してもよい。 (Nanocrystal manufacturing method)
The method for producing nanocrystals according to the present embodiment includes a method for producing nanocrystals of lead zirconate titanate Pb (Zr x Ti 1-x ) O 3 (0 <x <1) (PZT) using lead acetate (II). A) a step of heating and synthesizing a precursor solution starting from trihydrate, an aqueous solution of a water-soluble titanium complex and an aqueous solution of a water-soluble zirconium complex, and using a solution obtained by mixing an aqueous solution of sodium hydroxide and an organic carboxylic acid. With this configuration, a nanocrystal having at least one of the (100) plane, the (010) plane, and the (001) plane as a facet can be stably manufactured.
Further, an amine compound may be mixed with the precursor solution in addition to the aqueous sodium hydroxide solution and the organic carboxylic acid.
　本実施形態に係るナノ結晶の製造方法は、所望の組成になるように、上述した混合溶液において、チタンとジルコニウムとのモル比を調整して、水溶性チタン錯体と水溶性ジルコニウム錯体とを混合する。当該工程を行い、混合溶液のチタンとジルコニウムとのモル比を調整することで、任意の組成のナノ結晶を合成することができる。
　なお、チタン酸鉛ＰｂＴｉＯ３（ＰＴ）のナノ結晶を合成する場合はジルコニウムのモル比を０とし、ジルコン酸鉛ＰｂＺｒＯ３（ＰＺ）のナノ結晶を合成する場合はチタンのモル比を０とする。 In the method for producing a nanocrystal according to the present embodiment, a water-soluble titanium complex and a water-soluble zirconium complex are mixed in the above-mentioned mixed solution by adjusting the molar ratio of titanium and zirconium so that the desired composition is obtained. I do. By performing this step and adjusting the molar ratio between titanium and zirconium in the mixed solution, a nanocrystal having an arbitrary composition can be synthesized.
The molar ratio of zirconium is set to 0 when synthesizing lead titanate PbTiO 3 (PT) nanocrystals, and the molar ratio of titanium is set to 0 when synthesizing lead zirconate PbZrO 3 (PZ) nanocrystals. .
　また、本実施形態に係る他のナノ結晶の製造方法は、チタン酸鉛ＰｂＴｉＯ３（ＰＴ）のナノ結晶を製造する場合、酢酸鉛（II）三水和物に水酸化ナトリウム水溶液を添加した後、水溶性チタン錯体水溶液、アミン化合物、有機カルボン酸を混合した溶液を用いて加熱合成する工程をさらに含む。当該工程を行うことで、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有するチタン酸鉛ＰｂＴｉＯ３（ＰＴ）のナノ結晶を安定して製造することができる。 Another method for producing nanocrystals according to the present embodiment is that, when producing nanocrystals of lead titanate PbTiO 3 (PT), an aqueous solution of sodium hydroxide is added to lead (II) acetate trihydrate. And a step of performing heat synthesis using a solution in which a water-soluble titanium complex aqueous solution, an amine compound, and an organic carboxylic acid are mixed. By performing this step, it is possible to stably produce a lead titanate PbTiO 3 (PT) nanocrystal having at least one of the (100) plane, the (010) plane, and the (001) plane as a facet. it can.
　本実施形態で用いる水溶性チタン錯体としては、水に溶解された後チタン原子から配位子がはずれてチタン原子と酸素原子との結合が形成されるような化合物を用いることができる。そのような化合物としては、水溶性チタン錯体の配位子がヒドロキシカルボン酸の錯体等が挙げられる。配位子としてヒドロキシカルボン酸を有する錯体は、水に溶けやすい水溶性錯体である。 化合物 As the water-soluble titanium complex used in the present embodiment, a compound that dissolves in water, removes a ligand from a titanium atom, and forms a bond between a titanium atom and an oxygen atom can be used. Examples of such compounds include complexes of a water-soluble titanium complex with a hydroxycarboxylic acid as a ligand. A complex having a hydroxycarboxylic acid as a ligand is a water-soluble complex that is easily soluble in water.
　具体的には、ヒドロキシカルボン酸の例としては、乳酸、リンゴ酸、クエン酸、酒石酸、グリセリン酸、２－ヒドロキシ酪酸、ロイシン酸（＝２－ヒドロキシ－４－メチルペンタン酸）、キナ酸、マンデル酸（＝２－ヒドロキシ－２－フェニル酢酸）、グリコール酸等を挙げることができる。水溶性チタン錯体としては例えば、配位子が乳酸であるチタニウムビス（アンモニウムラクテート）ジヒドロキシド（Titanium bis(ammonium lactate) dihydroxide、以下「ＴＡＬＨ」）、配位子がグリコール酸（HOCH2COOH）である(NH4)6[Ti4(C2H2O3)4(C2H3O3)2(O2)4O2]・6H2O、配位子がクエン酸（（CH2COOH)2C(OH)COOH）である(NH4)8[Ti4(C6H4O7)4(O2)4]・8H2O、又は配位子がリンゴ酸（CH2CHOH(COOH)2）若しくは酒石酸（(CHOH)2(COOH)2）であるチタン錯体などが挙げられる。 Specifically, examples of hydroxycarboxylic acids include lactic acid, malic acid, citric acid, tartaric acid, glyceric acid, 2-hydroxybutyric acid, leucic acid (= 2-hydroxy-4-methylpentanoic acid), quinic acid, and mandel Acids (= 2-hydroxy-2-phenylacetic acid), glycolic acid and the like can be mentioned. Examples of the water-soluble titanium complex include titanium bis (ammonium lactate) dihydroxide (hereinafter referred to as “TALH”) in which the ligand is lactic acid, and the ligand is glycolic acid (HOCH 2 COOH). There is (NH 4 ) 6 [Ti 4 (C 2 H 2 O 3 ) 4 (C 2 H 3 O 3 ) 2 (O 2 ) 4 O 2 ] · 6H 2 O, and the ligand is citric acid ((CH 2 (COOH) 2 C (OH) COOH) (NH 4 ) 8 [Ti 4 (C 6 H 4 O 7 ) 4 (O 2 ) 4 ] · 8H 2 O, or the ligand is malic acid (CH 2 CHOH Titanium complexes which are (COOH) 2 ) or tartaric acid ((CHOH) 2 (COOH) 2 ).
　本実施形態では、水溶性チタン錯体としてＴＡＬＨを用好ましく用いることができる。ＴＡＬＨは水に可溶なチタンを含む酸化物の前駆体であり、ＴＡＬＨを用いた酸化物の形成反応は、他の方法と比べて穏やかな条件で反応が進行する。また、ＴＡＬＨが水に可溶であるため水溶液中での反応が可能である。こうした配位子がヒドロキシカルボン酸である水溶性チタン錯体を用いることにより、制御されたナノメートルサイズの六面体状の構造を有する、一般式Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表されるナノ結晶の合成をすることができる。 In the present embodiment, TALH can be preferably used as the water-soluble titanium complex. TALH is a precursor of an oxide containing titanium that is soluble in water, and the reaction of forming an oxide using TALH proceeds under milder conditions than other methods. Further, since TALH is soluble in water, the reaction can be performed in an aqueous solution. By using a water-soluble titanium complex whose ligand is a hydroxycarboxylic acid, a nanocrystal represented by the general formula Pb (Zr, Ti) O 3 having a controlled nanometer-sized hexahedral structure is obtained. Can be synthesized.
　水溶性ジルコニウム錯体としては、水に溶解された後ジルコニウム原子から配位子がはずれてジルコニウム原子と酸素原子との結合が形成されるような化合物を用いることができる。そのような化合物としては、水溶性ジルコニウム錯体の配位子がヒドロキシカルボン酸を用いることが好ましい。 (4) As the water-soluble zirconium complex, a compound that dissolves in water, removes a ligand from the zirconium atom, and forms a bond between the zirconium atom and the oxygen atom can be used. As such a compound, it is preferable that the ligand of the water-soluble zirconium complex is hydroxycarboxylic acid.
　具体的には、ヒドロキシカルボン酸の例としては、乳酸、リンゴ酸、クエン酸、酒石酸、グリセリン酸、２－ヒドロキシ酪酸、ロイシン酸（＝２－ヒドロキシ－４－メチルペンタン酸）、キナ酸、マンデル酸（＝２－ヒドロキシ－２－フェニル酢酸）、グリコール酸等を挙げることができる。水溶性ジルコニウム錯体としては例えば、ジルコニウムラクテートアンモニウム塩などが挙げられる。 Specifically, examples of hydroxycarboxylic acids include lactic acid, malic acid, citric acid, tartaric acid, glyceric acid, 2-hydroxybutyric acid, leucic acid (= 2-hydroxy-4-methylpentanoic acid), quinic acid, and mandel Acids (= 2-hydroxy-2-phenylacetic acid), glycolic acid and the like can be mentioned. Examples of the water-soluble zirconium complex include zirconium lactate ammonium salt.
　本実施形態では、水溶性ジルコニウム錯体としてジルコニウムラクテートアンモニウム塩（Zr(OH)[(OCH(CH3)COO-]3(NH4 +)3）を好ましく用いることができる。具体的には、オルガチックスＺＣ－３００（商品名：マツモトファインケミカル株式会社）が挙げられる。こうした配位子がヒドロキシカルボン酸である水溶性ジルコニウム錯体を用いることにより、制御されたナノメートルサイズの六面体状の構造を有する、一般式Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表されるナノ結晶の合成をすることができる。 In the present embodiment, a zirconium lactate ammonium salt (Zr (OH) [(OCH (CH 3 ) COO-] 3 (NH 4 + ) 3 ) can be preferably used as the water-soluble zirconium complex. Chix ZC-300 (trade name: Matsumoto Fine Chemical Co., Ltd.) By using a water-soluble zirconium complex in which such a ligand is hydroxycarboxylic acid, the ligand has a controlled nanometer-sized hexahedral structure. Nanocrystals represented by the general formula Pb (Zr, Ti) O 3 can be synthesized.
　本実施形態で用いるアミン化合物としては、窒素原子の非共有電子対が反応に寄与し得る化合物を用いることができる。そのような化合物としては、例えばｔｅｒｔ－ブチルアミン又はｎ－ブチルアミンが挙げられるが、特にｔｅｒｔ－ブチルアミンを用いることが好ましい。 ア ミ ン As the amine compound used in the present embodiment, a compound in which an unshared electron pair of a nitrogen atom can contribute to the reaction can be used. Such compounds include, for example, tert-butylamine or n-butylamine, and it is particularly preferable to use tert-butylamine.
　本発明で用いる有機カルボン酸としては、ナノ結晶合成の間、ナノ結晶の（１００）面、（０１０）面又は（００１）面に配位して、ナノ結晶の（１００）面、（０１０）面又は（００１）面の結晶成長を抑制することができる化合物を用いることができる。そのような化合物としてオレイン酸が挙げられるが、デカン酸（カプリン酸）ＣＨ３（ＣＨ２）８ＣＯＯＨなど炭素鎖が長いカルボン酸であれば、二重結合を含まないものであっても使用することができる。 The organic carboxylic acid used in the present invention may be coordinated to the (100) plane, (010) plane or (001) plane of the nanocrystal during the synthesis of the nanocrystal to form the (100) plane or (010) plane of the nanocrystal. A compound that can suppress the crystal growth of the (001) plane or the (001) plane can be used. Oleic acid may be mentioned as such a compound, but a carboxylic acid having a long carbon chain such as decanoic acid (capric acid) CH 3 (CH 2 ) 8 COOH may be used even if it does not contain a double bond. be able to.
　本実施形態に係るナノ結晶の製造方法において、アミン化合物をｔｅｒｔ－ブチルアミンとし、有機カルボン酸をオレイン酸とすると制御された六面体状の構造を有する、一般式Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表されるナノ結晶を合成することができる。 In the nanocrystal manufacturing method according to the present embodiment, the amine compound is represented by a general formula Pb (Zr, Ti) O 3 having a controlled hexahedral structure in which tert-butylamine is used and the organic carboxylic acid is oleic acid. Nanocrystals can be synthesized.
　本実施形態において反応溶液のｐＨは水酸化ナトリウム水溶液を添加することによって調節される。添加される水酸化ナトリウム水溶液の濃度は、１ｍｏｌ／Ｌ以上１０ｍｏｌ／Ｌ以下となるように決定されるが、好ましくは、４ｍｏｌ／Ｌ以上８ｍｏｌ／Ｌ以下であり、前記濃度が５ｍｏｌ／Ｌ以上７．５ｍｏｌ／Ｌ以下であることがより好ましい。 に お い て In this embodiment, the pH of the reaction solution is adjusted by adding an aqueous solution of sodium hydroxide. The concentration of the aqueous sodium hydroxide solution to be added is determined so as to be 1 mol / L or more and 10 mol / L or less, preferably 4 mol / L or more and 8 mol / L or less, and the concentration is 5 mol / L or more and 7 mol / L or less. More preferably, it is not more than 0.5 mol / L.
　上記濃度を上述の範囲以上とすることで、合成反応を十分に進行することができる。また、上記濃度を上述の範囲以下とすることでナノ結晶の凝集を抑制することができる。 合成 By setting the above concentration to the above range or more, the synthesis reaction can sufficiently proceed. In addition, by setting the concentration to be equal to or less than the above range, aggregation of nanocrystals can be suppressed.
　ここで、水酸化ナトリウム（ＮａＯＨ）水溶液はｐＨ調整剤として添加している。水熱合成においてｐＨ調整剤としてよく用いられるアンモニアでは合成が進みやすい十分な強塩基条件になりにくいが（ｐＨ１４の条件にさらにアンモニアを加えてもより強塩基にはならないが）。これに対して、ｐＨ調整剤として水酸化ナトリウム（ＮａＯＨ）を用いることで、反応溶液は十分な強塩基条件になり、一般式Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表されるナノ結晶の合成が進みやすい。 Here, an aqueous solution of sodium hydroxide (NaOH) is added as a pH adjuster. Ammonia, which is often used as a pH adjuster in hydrothermal synthesis, is unlikely to have sufficient strong base conditions to facilitate synthesis (although adding ammonia to the pH 14 condition will not result in a stronger base). On the other hand, by using sodium hydroxide (NaOH) as a pH adjuster, the reaction solution becomes a sufficiently strong base condition, and the synthesis of the nanocrystal represented by the general formula Pb (Zr, Ti) O 3 is performed. Easy to go.
　本実施形態に係るナノ結晶の製造方法によれば、酢酸鉛（II）三水和物、水溶性チタン錯体水溶液および水溶性ジルコニウム錯体水溶液を出発原料とする前駆体溶液に、水酸化ナトリウム水溶液および有機カルボン酸（必要に応じてさらにアミン化合物）を混合した溶液において、混合する水酸化ナトリウムの濃度が１ｍｏｌ／Ｌ以上１０ｍｏｌ／Ｌ以下であることにより、合成反応を十分に進行させることができ、かつナノ結晶の凝集を抑制することができる。 According to the method for producing nanocrystals according to the present embodiment, a sodium hydroxide aqueous solution and a precursor solution starting from a lead (II) acetate trihydrate, a water-soluble titanium complex aqueous solution and a water-soluble zirconium complex aqueous solution are used as starting materials. When the concentration of sodium hydroxide to be mixed is 1 mol / L or more and 10 mol / L or less in a solution in which an organic carboxylic acid (an amine compound is further added as necessary), the synthesis reaction can sufficiently proceed, In addition, aggregation of nanocrystals can be suppressed.
　本実施形態の溶液において、鉛１モルに対するアミン化合物のモル数が０以上１２０以下であることが好ましく、０以上９０以下であることがより好ましい。
　また、本発明の溶液において、鉛１モルに対する有機カルボン酸のモル数が１以上３０以下であることが好ましい。
　鉛１モルに対する有機カルボン酸のモル数を当該範囲とすることで、ナノ結晶の形状を十分に制御し、きれいな六面体を形成することができる。 In the solution of the present embodiment, the number of moles of the amine compound per mole of lead is preferably 0 or more and 120 or less, more preferably 0 or more and 90 or less.
Further, in the solution of the present invention, it is preferable that the number of moles of the organic carboxylic acid is 1 or more and 30 or less with respect to 1 mole of lead.
By setting the number of moles of the organic carboxylic acid per mole of lead within the above range, the shape of the nanocrystal can be sufficiently controlled, and a clean hexahedron can be formed.
　本実施形態の反応溶液の加熱は、１４０℃以上２９０℃以下の温度で実施されることが好ましく、１７０℃以上２７０℃以下の温度で実施されることがより好ましく、２００℃以上２５０以下の温度で実施されることがさらに好ましい。当該温度で加熱を行うことにより、合成反応が十分に進行し、かつ、反応中にナノ結晶表面に配位した有機カルボン酸が脱離したり、反応溶液内で有機カルボン酸が分離したりしてしまうことを回避して、制御された六面体状の構造を持つナノ結晶が得られやすくなる。 The heating of the reaction solution of this embodiment is preferably performed at a temperature of 140 ° C. or more and 290 ° C. or less, more preferably 170 ° C. or more and 270 ° C. or less, and a temperature of 200 ° C. or more and 250 or less. More preferably, it is performed. By performing the heating at the temperature, the synthesis reaction proceeds sufficiently, and the organic carboxylic acid coordinated to the nanocrystal surface during the reaction is eliminated or the organic carboxylic acid is separated in the reaction solution. By avoiding this, it becomes easier to obtain nanocrystals having a controlled hexahedral structure.
　本発明の反応溶液の加熱は、１時間以上８０時間以下の間実施されることが好ましく、４８時間以上７２時間以下の間実施されることがより好ましい。加熱時間を１時間以上未満とすることで合成反応を十分に進行することができる。また、加熱時間が８０時間を超えてもナノ結晶の形状はさほど変化しないため、これ以上の加熱は必要ではないと考えられる。 加熱 The heating of the reaction solution of the present invention is preferably carried out for 1 hour to 80 hours, more preferably for 48 hours to 72 hours. When the heating time is less than 1 hour, the synthesis reaction can proceed sufficiently. Further, even if the heating time exceeds 80 hours, the shape of the nanocrystals does not change so much, so it is considered that no further heating is necessary.
　本実施形態において反応溶液を加熱して反応を進行させるには既に知られている様々な方法を適宜使用することができるが、水熱合成を用いることが好ましい。 に お い て In the present embodiment, various known methods can be appropriately used to heat the reaction solution to cause the reaction to proceed, but it is preferable to use hydrothermal synthesis.
　本実施形態に係るナノ結晶の製造方法によれば、加熱を、１４０℃以上２９０℃以下の温度で、かつ１時間以上８０時間以下の間実施することにより、合成反応を十分に進行させかつ無駄な加熱を実施することなく、制御された六面体状の構造を持つナノ結晶を得ることができる。 According to the nanocrystal manufacturing method according to the present embodiment, the heating is performed at a temperature of 140 ° C. or more and 290 ° C. or less and for 1 hour or more and 80 hours or less, so that the synthesis reaction can sufficiently proceed and wasteful A nanocrystal having a controlled hexahedral structure can be obtained without performing any appropriate heating.
　本実施形態は、合成の後、前記溶液を遠心分離して沈殿物を回収することが好ましい。 は In this embodiment, after the synthesis, it is preferable that the solution is centrifuged to collect a precipitate.
　本実施形態のナノ結晶の製造方法によれば、合成の後溶液を遠心分離して沈殿物を回収することにより、不要な小さな結晶などを取り除き、制御された六面体状の構造を持つナノ結晶を得ることができる。 According to the nanocrystal manufacturing method of the present embodiment, by collecting the precipitate by centrifuging the solution after synthesis, unnecessary small crystals and the like are removed, and a nanocrystal having a controlled hexahedral structure is obtained. Obtainable.
（電子デバイス）
　本実施形態の電子デバイスは、上述の実施形態に係るナノ結晶を含む薄膜を有する。
　この電子デバイスは、強誘電体又は反強誘電体の特性を利用する公知の電子デバイスである。電子デバイスとしては、例えば、メモリデバイス、センサー、アクチュエータなどが挙げられる。 (Electronic device)
The electronic device of the present embodiment has the thin film including the nanocrystal according to the above-described embodiment.
This electronic device is a known electronic device that utilizes the characteristics of a ferroelectric or antiferroelectric. Examples of the electronic device include a memory device, a sensor, and an actuator.
　薄膜は、特許文献４に開示されている方法を用いて作製できる。すなわち、上述の実施形態にナノ結晶を含む薄膜は、具体的には、混合工程と配列工程とを有する方法で作製することができる。混合工程は、Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表される本発明のナノ結晶と非極性溶媒とを容器に入れ混合し、Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表される本発明のナノ結晶を含む分散液を得る工程である。配列工程は、混合工程で得た分散液に基板を浸漬し、引き上げることにより、表面張力を利用して塗布し、ナノ結晶を基板上に配列させる工程である。 The thin film can be manufactured using the method disclosed in Patent Document 4. That is, the thin film including the nanocrystals in the above-described embodiment can be specifically produced by a method having a mixing step and an arrangement step. Mixing process, Pb (Zr, Ti) a nanocrystal and a non-polar solvent of the present invention represented by O 3 were mixed in a container, Pb (Zr, Ti) nanocrystals of the present invention represented by O 3 This is a step of obtaining a dispersion containing: The arranging step is a step in which the substrate is immersed in the dispersion obtained in the mixing step, and is then lifted up to apply the solution using surface tension, thereby arranging the nanocrystals on the substrate.
（圧電素子）
　本実施形態の圧電素子は、上記実施形態に記載のナノ結晶を含む薄膜と、この薄膜を挟むように設けられた一対の電極とを備える。 (Piezoelectric element)
The piezoelectric element of the present embodiment includes the thin film containing the nanocrystal described in the above embodiment, and a pair of electrodes provided so as to sandwich the thin film.
　電極としては、Ｐｔ、Ｉｒ、Ｒｕ等の導電性を有し、かつ強誘電体膜と反応しない材料によって形成される。 The electrode is formed of a material having conductivity, such as Pt, Ir, and Ru, and which does not react with the ferroelectric film.
〔チタン酸ジルコン酸鉛ナノ結晶（Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（原料仕込み組成；ｘ＝０．５２））の合成及び同定〕
（１）実施例１
　以下の手順に従って、チタン酸ジルコン酸鉛ナノ結晶を合成した。
　ＰＺＴ前駆体溶液３ｍｌ（酢酸鉛（II）三水和物（Ｐｂ（ＣＨ３ＣＯＯ）２・３Ｈ２Ｏ）０．８９２ｍｍｏｌ、ＴＡＬＨ　０．４２８ｍｍｏｌ、ＺＣ－３００（商品名）０．４６４ｍｍｏｌ含有）を４２ｍｌの水に溶解した。この水溶液を撹拌しながら、５ｍｏｌ／Ｌの水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸を添加して反応溶液を調整した。鉛（Ｐｂ）、水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：１２：１２となるように調整した。このように調製された溶液をオートクレーブに入れて密閉し、２３０℃の温度で７２時間加熱した後、室温まで冷却した。その後反応生成物を含む溶液を遠心分離して沈殿物を回収した。 [Synthesis and identification of lead zirconate titanate nanocrystals (Pb (Zr x Ti 1-x ) O 3 (raw material preparation composition; x = 0.52)]]
(1) Example 1
According to the following procedure, lead zirconate titanate nanocrystals were synthesized.
3 ml of PZT precursor solution (containing 0.892 mmol of lead (II) acetate trihydrate (Pb (CH 3 COO) 2 .3H 2 O), 0.428 mmol of TALH, and 0.464 mmol of ZC-300 (trade name)) Dissolved in 42 ml of water. While stirring this aqueous solution, a 5 mol / L aqueous solution of sodium hydroxide, tert-butylamine and oleic acid were added to prepare a reaction solution. The molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was adjusted to be 1: 12: 12: 12. The solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
　実施例１のナノ結晶は、走査電子顕微鏡（日本電子株式会社製ＪＥＯＬ、ＪＳＭ－６３３５ＦＭ、１０ｋＶ）、透過型電子顕微鏡（ＦＥＩ製Ｔｅｃｎａｉ Ｏｓｉｒｉｓ、２００ｋＶ）を用いて観察し、エネルギー分散型蛍光Ｘ線分析装置（ＥＤＸＲＦ）（株式会社島津製作所、ＥＤＸ－８０００）、および、透過型電子顕微鏡（ＦＥＩ製ＴｅｃｎａｉＯｓｉｒｉｓ、２００ｋＶ）の付属装置であるエネルギー分散型Ｘ線分析（ＥＤＸ）により解析した。結晶相の同定はＸ線回折装置（株式会社リガク製、ＳｍａｒｔＬａｂ、４０ｋＶ／３０ｍＡ）を用いて同定した。 The nanocrystals of Example 1 were observed using a scanning electron microscope (JEOL, JSM-6335FM, 10 kV, manufactured by JEOL Ltd.) and a transmission electron microscope (Tecnai @ Osiris, 200 kV, manufactured by FEI), and energy dispersive X-ray fluorescence. Analysis was performed by an analyzer (EDXRF) (EDX-8000, Shimadzu Corporation) and energy dispersive X-ray analysis (EDX) as an accessory device of a transmission electron microscope (TecnaiOsiris, 200 kV, manufactured by FEI). The crystal phase was identified using an X-ray diffractometer (SmartLab, 40 kV / 30 mA, manufactured by Rigaku Corporation).
　ナノ結晶の各種同定用サンプルは、遠心分離により回収した粉末をエタノールに再分散させたコロイド溶液を用い、シリコンウェハ基板へ室温にて滴下乾燥することにより作製した。サンプルに紫外線照射２時間を行った後、インキュベータ内において２００℃で１．５時間保持して、表面の清浄化を行った。他の実施例のナノ結晶の各種同定用サンプルについても同様である。 各種 Samples for identification of nanocrystals were prepared by using a colloidal solution obtained by re-dispersing powder recovered by centrifugation in ethanol at room temperature and drying it on a silicon wafer substrate. After irradiating the sample with ultraviolet light for 2 hours, the sample was kept at 200 ° C. for 1.5 hours in an incubator to clean the surface. The same applies to various samples for identification of nanocrystals of other examples.
　図１に、上記のサンプル作製方法によって、実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　ＳＥＭ像から、実施例１において、１ｎｍ以上３００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上１５０ｎｍ以下のナノ結晶が全体の７０％以上であった。 FIG. 1 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing nanocrystals of lead zirconate titanate prepared in Example 1 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
From the SEM image, in Example 1, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
　図２に、実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 2 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 1. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 1 had a perovskite structure with a space group of P4 mm.
　図３に、実施例１で作製したチタン酸ジルコン酸鉛ナノ結晶の高倍率のＴＥＭ像を示す。
　ＴＥＭ像観察用のサンプルは、チタン酸ジルコン酸鉛ナノ結晶を含む分散液を濾紙上に配置したＴＥＭグリッド（基板）上に滴下し、滴下した分散液中の溶媒を濾紙に吸収させて除去して作製した。
　図３に示す高倍率のＴＥＭ像において、２個のナノ結晶が観察でき、大きな範囲を示している右側のナノ結晶のＴＥＭ像において、直交する２つのファセットの存在を確認できる。具体的には、図３に示すチタン酸鉛ジルコン酸鉛ナノ結晶１は、ファセットＡ１およびファセットＡ２を有する。また、図３に示す高倍率のＴＥＭ像において、段差構造も観察することができる。 FIG. 3 shows a high magnification TEM image of the lead zirconate titanate nanocrystals prepared in Example 1.
For the sample for TEM image observation, a dispersion containing lead zirconate titanate nanocrystals was dropped on a TEM grid (substrate) arranged on a filter paper, and the solvent in the dropped dispersion was absorbed by the filter paper and removed. Produced.
In the high magnification TEM image shown in FIG. 3, two nanocrystals can be observed, and in the TEM image of the right nanocrystal showing a large range, the presence of two orthogonal facets can be confirmed. Specifically, lead titanate zirconate nano crystal 1 shown in FIG. 3 has a facet A 1 and facet A 2. In addition, a step structure can also be observed in the high-magnification TEM image shown in FIG.
　図４Ａ及び図４Ｂはそれぞれ、ＴＥＭ像、その電子回折スポット像である。
　図４ＡのＳＥＭ像の左方及び下方のそれぞれに示した線図は、図４Ａに示したナノ結晶のシート状部分の側面の一部を象ったものであり、２か所の段差を示したものである。図４Ａに示したナノ結晶は部分的にシート状形状でかつ部分的に略六面体形状を有する形状であり、そのシート状部分の側面において段差を有するものである。
　図４Ｂにおける（１００）面の面間隔は、０．３９６ｎｍ及び０．３９７ｎｍであった。
　また、ＴＥＭ－ＥＤＸにより、得られたナノ結晶の組成比は、Ｐｂ：Ｚｒ：Ｔｉは１：０．１３：０．７０であった。 4A and 4B are a TEM image and an electron diffraction spot image thereof, respectively.
The diagram shown on the left and below the SEM image of FIG. 4A, respectively, shows a part of the side surface of the sheet portion of the nanocrystal shown in FIG. 4A and shows two steps. It is something. The nanocrystal shown in FIG. 4A has a partially sheet-like shape and a partially hexagonal shape, and has a step on the side surface of the sheet-like portion.
The plane spacing of the (100) plane in FIG. 4B was 0.396 nm and 0.397 nm.
Further, according to TEM-EDX, the composition ratio of the obtained nanocrystals was 1: 0.13: 0.70 for Pb: Zr: Ti.
　図４Ｃは、本発明の典型的なナノ結晶が持つ特徴を説明するために模式的に示した斜視図である（図４Ａで示したナノ結晶に対応する模式図ではない）。
　図４Ｃに示すナノ結晶は、シート状形状の部分（シート状部）上に略六面体形状を有する部分（略六面体形状部）が載っている形状を有するものであり、そのシート状部の側面において段差構造を有するものである。この模式図において平坦な面は、（１００）面、（０１０）面および（００１）面のいずれかのファセットを示すものである。 FIG. 4C is a schematic perspective view (not a schematic view corresponding to the nanocrystal shown in FIG. 4A) for explaining characteristics of typical nanocrystals of the present invention.
The nanocrystal shown in FIG. 4C has a shape in which a portion having a substantially hexahedral shape (substantially hexahedral portion) is placed on a sheet-shaped portion (sheet-shaped portion). It has a step structure. In this schematic diagram, the flat surface indicates any of the facets (100), (010), and (001).
　（２）実施例２
　鉛（Ｐｂ）、水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：１２：１５となるように反応溶液を調整した以外は実施例１と同様の方法で、チタン酸ジルコン酸鉛ナノ結晶の合成を行った。 (2) Example 2
Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted such that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 12: 15. Lead acid nanocrystals were synthesized.
　図５に、上記のサンプル作製方法によって、実施例２で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　ＳＥＭ像から、実施例２において、１ｎｍ以上３００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上１５０ｎｍ以下のナノ結晶が全体の７０％以上であった。 FIG. 5 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing lead zirconate titanate nanocrystals prepared in Example 2 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
From the SEM image, in Example 2, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
　図６に、実施例２で作製したチタン酸ジルコン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例２で作製したチタン酸ジルコン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 6 shows a powder XRD pattern of the lead zirconate titanate nanocrystals produced in Example 2. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 2 had a perovskite structure with a space group of P4 mm.
（３）実施例３
　鉛（Ｐｂ）、水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：０：１５となるように反応溶液を調整した以外は実施例１と同様の方法で、チタン酸ジルコン酸鉛ナノ結晶の合成を行った。実施例３はアミン化合物を用いなかった場合である。 (3) Example 3
Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted so that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 0: 15. Lead acid nanocrystals were synthesized. Example 3 is a case where no amine compound was used.
　図７に、上記のサンプル作製方法によって、実施例３で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　図７においてほぼ中央に位置するナノ結晶（矢印の延長上に位置するナノ結晶）は、図７のＳＥＭ像の右方に示したようなシート状形状のナノ結晶である。このナノ結晶の厚さは１６ｎｍであり、面拡がり方向のサイズのうち最大のサイズは８０ｎｍ程度であるから、面拡がり方向のサイズのうち最大のサイズと厚み方向のサイズの比は、５：１程度である。
　　ＳＥＭ像から、実施例３において、１ｎｍ以上３００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上１５０ｎｍ以下のナノ結晶が全体の７０％以上であった。 FIG. 7 shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 3 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
In FIG. 7, the nanocrystal located substantially at the center (the nanocrystal located on the extension of the arrow) is a sheet-shaped nanocrystal as shown on the right side of the SEM image in FIG. Since the thickness of the nanocrystal is 16 nm and the largest size in the plane spreading direction is about 80 nm, the ratio of the largest size in the plane spreading direction to the size in the thickness direction is 5: 1. It is about.
From the SEM image, in Example 3, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals of 1 nm or more and 150 nm or less 70% or more.
　図８に、実施例３で作製したチタン酸ジルコン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例３で作製したチタン酸ジルコン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 8 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 3. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 3 had a perovskite structure with a space group of P4 mm.
　また、ＥＤＸＲＦを用いて、ファンダメンタル・パラメータ法により、シリコンウェハ上に滴下乾燥させたナノ結晶を含むサンプルの組成比を分析した結果、Ｐｂ：Ｚｒ：Ｔｉは１：０．１５：０．５７であった。 In addition, as a result of analyzing the composition ratio of the sample including the nanocrystals dropped and dried on the silicon wafer by the fundamental parameter method using EDXRF, Pb: Zr: Ti was 1: 0.15: 0.57. there were.
（４）実施例４
　鉛（Ｐｂ）、水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：３６：１５となるように反応溶液を調整した以外は実施例１と同様の方法で、チタン酸ジルコン酸鉛ナノ結晶の合成を行った。 (4) Example 4
Zircon titanate was prepared in the same manner as in Example 1 except that the reaction solution was adjusted so that the molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was 1: 12: 36: 15. Lead acid nanocrystals were synthesized.
　図９Ａに、上記のサンプル作製方法によって、実施例４で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　ＳＥＭ像から、実施例４において、１ｎｍ以上１００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上３０ｎｍ以下のナノ結晶が全体の７０％以上であった。 FIG. 9A shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 4 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
From the SEM image, in Example 4, nanocrystals having a size of 1 nm or more and 100 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary positions, the nanocrystals having a size of 1 nm or more and 30 nm or less were 70% or more.
　図１０に、実施例４で作製したチタン酸ジルコン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例４で作製したチタン酸ジルコン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 10 shows a powder XRD pattern of the lead zirconate titanate nanocrystals prepared in Example 4. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 4 had a perovskite structure with a space group of P4 mm.
〔チタン酸ジルコン酸鉛ナノ結晶（Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（原料仕込み組成；ｘ＝０．７））の合成〕
（１）実施例５
　以下の手順に従って、チタン酸ジルコン酸鉛ナノ結晶を合成した。
　ＰＺＴ前駆体溶液３ｍｌ（酢酸鉛（II）三水和物（Ｐｂ（ＣＨ３ＣＯＯ）２・３Ｈ２Ｏ）（０．８９２）ｍｍｏｌ、ＴＡＬＨ　（０．２６８）ｍｍｏｌ、ＺＣ－３００（商品名）（０．６２４）ｍｍｏｌ含有）を、４２ｍｌの水に溶解した。この水溶液を撹拌しながら、５ｍｏｌ／Ｌの水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸を添加して反応溶液を調整した。鉛（Ｐｂ）、水酸化ナトリウム水溶液、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：１２：１５となるように調整した。このように調製された溶液をオートクレーブに入れて密閉し、２３０℃の温度で７２時間加熱した後、室温まで冷却した。その後反応生成物を含む溶液を遠心分離して沈殿物を回収した。 [Synthesis of Lead Zirconate Titanate Nanocrystals (Pb (Zr x Ti 1-x ) O 3 (composition of raw materials; x = 0.7))]
(1) Example 5
According to the following procedure, lead zirconate titanate nanocrystals were synthesized.
3 ml of PZT precursor solution (lead (II) acetate trihydrate (Pb (CH 3 COO) 2 .3H 2 O) (0.892) mmol, TALH (0.268) mmol, ZC-300 (trade name) (0.624 mmol) was dissolved in 42 ml of water. While stirring this aqueous solution, a 5 mol / L aqueous solution of sodium hydroxide, tert-butylamine and oleic acid were added to prepare a reaction solution. The molar ratio of lead (Pb), aqueous sodium hydroxide, tert-butylamine and oleic acid was adjusted to be 1: 12: 12: 15. The solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
　図１１Ａに、上記のサンプル作製方法によって、実施例５で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　図１１ＡのＳＥＭ像の右方に示した線図は、図１１Ａにおいて中央下側に位置するナノ結晶のシート状部分の側面の一部を象ったものであり、２か所の段差を図示した。そのナノ結晶は部分的にシート状形状でかつ部分的に略六面体形状を有する形状であり、そのシート状部分の側面において段差を有するものである。
　　ＳＥＭ像から、実施例５において、１ｎｍ以上３００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上１５０ｎｍ以下のナノ結晶が全体の７０％以上であった。図１１Ｂは、シート状ナノ結晶１Ｃの一例の概形を模式的に示す斜視図である。シート状ナノ結晶１Ｃは側面２０Ａに複数の段差構造２１とファセットを有する。図１１Ｂに示すナノ結晶１Ｃはファセットの一部であるファセットＡ８、Ａ９、Ａ１０、Ａ１１が示されている。 FIG. 11A shows an SEM image of the surface of a sample prepared by drop-drying a dispersion containing nanocrystals of lead zirconate titanate prepared in Example 5 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
The diagram shown on the right side of the SEM image in FIG. 11A shows a part of the side surface of the sheet portion of the nanocrystal located at the lower center in FIG. 11A, and shows two steps. did. The nanocrystal has a partially sheet-like shape and a partially hexahedral shape, and has a step on the side surface of the sheet-like portion.
From the SEM image, in Example 5, nanocrystals having a size of 1 nm or more and 300 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary locations, the nanocrystals having a size of 1 nm or more and 150 nm or less 70% or more. FIG. 11B is a perspective view schematically showing an outline of an example of the sheet-like nanocrystal 1C. The sheet-like nanocrystal 1C has a plurality of step structures 21 and facets on a side surface 20A. The nanocrystal 1C shown in FIG. 11B shows facets A 8 , A 9 , A 10 , and A 11 that are part of the facet.
　図１２に、実施例５で作製したチタン酸ジルコン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例５で作製したチタン酸ジルコン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 12 shows a powder XRD pattern of the lead zirconate titanate nanocrystals produced in Example 5. From the obtained XRD pattern, it was found that the lead zirconate titanate nanocrystals prepared in Example 5 had a perovskite structure with a space group of P4 mm.
　また、ＥＤＸＲＦを用いて、ファンダメンタル・パラメータ法により、シリコンウェハ上に滴下乾燥させたナノ結晶を含むサンプルの組成比を分析した結果、Ｐｂ：Ｚｒ：Ｔｉは１：０．２２：０．３５であった。 In addition, as a result of analyzing the composition ratio of the sample containing the nanocrystals dropped and dried on the silicon wafer by the fundamental parameter method using EDXRF, the ratio of Pb: Zr: Ti was 1: 0.22: 0.35. there were.
〔チタン酸鉛ナノ結晶（Ｐｂ（ＺｒｘＴｉ１－Ｘ）Ｏ３（原料仕込み組成；ｘ＝０））の合成〕
（１）実施例６
　以下の手順に従って、チタン酸鉛ナノ結晶を合成した。
　酢酸鉛（II）三水和物水溶液（Ｐｂ（ＣＨ３ＣＯＯ）２・３Ｈ２Ｏ）３ｍｍｏｌを、７．５ｍｏｌ／Ｌの水酸化ナトリウム水溶液３０ｍｌに溶解した。この溶液を撹拌しながら、ＴＡＬＨ　３ｍｍｏｌ、ｔｅｒｔ－ブチルアミン及びオレイン酸を添加して反応溶液を調整した。鉛（Ｐｂ）、ｔｅｒｔ－ブチルアミン及びオレイン酸のモル比が１：１２：１２となるように調整した。このように調製された溶液をオートクレーブに入れて密閉し、２３０℃の温度で７２時間加熱した後、室温まで冷却した。その後反応生成物を含む溶液を遠心分離して沈殿物を回収した。 [Synthesis of Lead Titanate Nanocrystals (Pb (Zr x Ti 1-x ) O 3 (composition of raw materials; x = 0))]
(1) Embodiment 6
According to the following procedure, lead titanate nanocrystals were synthesized.
3 mmol of an aqueous lead (II) acetate trihydrate solution (Pb (CH 3 COO) 2 .3H 2 O) was dissolved in 30 ml of a 7.5 mol / L aqueous sodium hydroxide solution. While stirring this solution, 3 mmol of TALH, tert-butylamine and oleic acid were added to prepare a reaction solution. The molar ratio of lead (Pb), tert-butylamine and oleic acid was adjusted to be 1:12:12. The solution thus prepared was put in an autoclave, sealed, heated at a temperature of 230 ° C. for 72 hours, and then cooled to room temperature. Thereafter, the solution containing the reaction product was centrifuged to collect a precipitate.
　図１３に、上記のサンプル作製方法によって、実施例６で作製したチタン酸ジルコン酸鉛ナノ結晶を含む分散液をシリコンウェハ基板上に室温にて滴下乾燥することにより作製したサンプルの表面のＳＥＭ像を示す。
　ＳＥＭ像から、実施例６において、１ｎｍ以上８００ｎｍ以下のサイズのナノ結晶を合成できていた。ナノ結晶のサイズ及びその分布は合成条件に依存するが、実施例１において、任意に場所を変えて得られた１０枚のＳＥＭ像の目視に基づくと、１ｎｍ以上５００ｎｍ以下のナノ結晶が全体の７０％以上であった。 FIG. 13 shows an SEM image of the surface of a sample prepared by dropping and drying the dispersion containing nanocrystals of lead zirconate titanate prepared in Example 6 on a silicon wafer substrate at room temperature by the above-described sample preparation method. Is shown.
From the SEM image, in Example 6, nanocrystals having a size of 1 nm or more and 800 nm or less could be synthesized. Although the size and distribution of the nanocrystals depend on the synthesis conditions, in Example 1, based on the visual observation of 10 SEM images obtained at arbitrary positions, the nanocrystals of 1 nm or more and 500 nm or less 70% or more.
　図１４に、実施例６で作製したチタン酸鉛ナノ結晶の粉末ＸＲＤパターンを示す。得られたＸＲＤパターンにより、実施例６で作製したチタン酸鉛ナノ結晶は空間群Ｐ４ｍｍのペロブスカイト構造を有することがわかった。 FIG. 14 shows a powder XRD pattern of the lead titanate nanocrystals produced in Example 6. From the obtained XRD pattern, it was found that the lead titanate nanocrystals produced in Example 6 had a perovskite structure with a space group of P4 mm.
　ＰＺＴはメモリデバイス、センサーおよびアクチュエータなど幅広い分野で応用されている材料である。ナノサイズの単結晶はバルクとは異なる特性を発現するため、結晶方位を揃えて三次元に集積することにより、結晶界面での相互作用等による特性向上が期待される。本発明のナノ結晶と特許文献４の製膜・集積技術とを組み合わせることにより、優れた特性を有する不揮発性メモリ素子あるいはエナジーハーベスタ等の圧電デバイス素子の作製が期待される。 PZT is a material that is applied in a wide range of fields such as memory devices, sensors and actuators. Since a nano-sized single crystal exhibits characteristics different from those of a bulk, it is expected that the characteristics are improved by the interaction at the crystal interface or the like by integrating the crystal orientation and three-dimensionally. By combining the nanocrystal of the present invention with the film formation / integration technology of Patent Document 4, it is expected to produce a non-volatile memory element having excellent characteristics or a piezoelectric device element such as an energy harvester.
〔実施例３のチタン酸ジルコン酸鉛ナノ結晶を含む分散液を用いたチタン酸ジルコン酸鉛（ＰＺＴ）膜の作製〕
（１）実施例７
　以下の手順に従って、チタン酸ジルコン酸鉛ナノ結晶を含むＰＺＴ膜を作製した。
　まず、実施例３で得られたチタン酸ジルコン酸鉛の粉末とトルエン（非極性溶媒）を容器に入れ、その容器を超音波に１０分間かけて結晶の分散の促進を図った。
　Ｐｔ／ＴｉＯｘ／ＳｉＯ２／Ｓｉ基板を、チタン酸ジルコン酸鉛分散液に浸漬し、１０ｎｍ／ｓｅｃの速度で引き上げ、乾燥することにより、Ｐｔ／ＴｉＯｘ／ＳｉＯ２／Ｓｉ基板上にチタン酸ジルコン酸鉛ナノ結晶を含むＰＺＴ膜が形成されたサンプルを得た。 [Production of Lead Zirconate Titanate (PZT) Film Using Dispersion Solution Containing Nanocrystals of Lead Zirconate Titanate of Example 3]
(1) Embodiment 7
A PZT film containing lead zirconate titanate nanocrystals was prepared according to the following procedure.
First, the powder of lead zirconate titanate obtained in Example 3 and toluene (a non-polar solvent) were placed in a container, and the container was subjected to ultrasonic waves for 10 minutes to promote dispersion of crystals.
A Pt / TiO x / SiO 2 / Si substrate is immersed in a lead titanate zirconate dispersion, pulled up at a speed of 10 nm / sec, and dried to form a titanic acid on the Pt / TiO x / SiO 2 / Si substrate. A sample on which a PZT film containing lead zirconate nanocrystals was formed was obtained.
　図１５に、得られたサンプルの表面のＳＥＭ像を示す。図１６に、図１５のＳＥＭ像より広範囲のＳＥＭ像を示す。
　ＳＥＭ像から、チタン酸ジルコン酸鉛ナノ結晶が配列して、凹凸が小さくて穴のない薄膜が形成されていることがわかった。 FIG. 15 shows an SEM image of the surface of the obtained sample. FIG. 16 shows a SEM image of a wider range than the SEM image of FIG.
From the SEM image, it was found that the lead zirconate titanate nanocrystals were arranged, and a thin film having no unevenness and no holes was formed.
　図１７に、このサンプルのＸＲＤパターンを示す。図１７においては、Ｐｔ／ＴｉＯｘ／ＳｉＯ２／Ｓｉ基板のＸＲＤパターンも示した。
　サンプルのＸＲＤパターンにおいて、図３の粉末ＸＲＤパターンと比較してチタン酸ジルコン酸鉛ナノ結晶の（００１）面の強いピークが確認でき、（００１）に優先配向していることが示された。 FIG. 17 shows an XRD pattern of this sample. FIG. 17 also shows the XRD pattern of the Pt / TiO x / SiO 2 / Si substrate.
In the XRD pattern of the sample, a strong peak of the (001) plane of the lead zirconate titanate nanocrystals was confirmed as compared with the powder XRD pattern of FIG. 3, indicating that the sample was preferentially oriented at (001).
　図１８に、このサンプルについて６００℃で熱処理を行った後、圧電応答顕微鏡を用いて測定したｄ３３－ＰＦＭ－Ｖ曲線を示す。電圧の印加に伴う圧電応答が得られ、圧電性を確認した。また、ヒステリシス特性が得られたことから、強誘電性を示すことが示唆された。 FIG. 18 shows a d33 -PFM- V curve measured by using a piezoelectric response microscope after heat-treating the sample at 600 ° C. A piezoelectric response was obtained with the application of the voltage, and the piezoelectricity was confirmed. In addition, since the hysteresis characteristics were obtained, it was suggested that they exhibited ferroelectricity.
　ＰＺＴはメモリデバイス、センサーおよびアクチュエータなど幅広い分野で応用されている材料である。ナノサイズの単結晶はバルクとは異なる特性を発現するため、結晶方位を揃えて三次元に集積することにより、結晶界面での相互作用等による特性向上が期待される。本発明のナノ結晶と特許文献４の製膜・集積技術とを組み合わせることにより、優れた特性を有する不揮発性メモリ素子あるいはエナジーハーベスタ等の圧電デバイス素子の作製が期待される。 PZT is a material that is applied in a wide range of fields such as memory devices, sensors and actuators. Since a nano-sized single crystal exhibits characteristics different from those of a bulk, it is expected that the characteristics are improved by the interaction at the crystal interface or the like by integrating the crystal orientation and three-dimensionally. By combining the nanocrystal of the present invention with the film formation / integration technology of Patent Document 4, it is expected to produce a non-volatile memory element having excellent characteristics or a piezoelectric device element such as an energy harvester.
　本発明のナノ結晶は、不揮発性メモリ、センサー、アクチュエータおよび圧電デバイスなどに利用可能である。 ナ ノ The nanocrystal of the present invention can be used for nonvolatile memories, sensors, actuators, piezoelectric devices, and the like.

Claims (15)

  1. 　Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３で表される単結晶であり、（１００）面、（０１０）面および（００１）面の少なくともいずれか一つをファセットとして有すると共に、サイズが１ｎｍ以上１０００ｎｍ以下であることを特徴とするナノ結晶。 A single crystal represented by Pb (Zr, Ti) O 3 having at least one of a (100) plane, a (010) plane and a (001) plane as a facet, and having a size of 1 nm or more and 1000 nm or less. A nanocrystal characterized by the following.
  2. 　結晶の形状は、シート状形状、略六面体形状、又は、部分的にシート状形状でかつ部分的に略六面体形状、のいずれかであることを特徴とする請求項１に記載のナノ結晶。 The nanocrystal according to claim 1, wherein the shape of the crystal is one of a sheet shape, a substantially hexahedral shape, or a partially sheet-like shape and a partially substantially hexahedral shape.
  3. 　前記結晶の形状がシート状形状、又は、部分的にシート状形状でかつ部分的に略六面体形状である場合に、シートの側面に段差を有することを特徴とする請求項２に記載のナノ結晶。 3. The nanocrystal according to claim 2, wherein the crystal has a sheet-like shape, or has a step on a side surface of the sheet when partially partially sheet-like and partially substantially hexahedral. 4. .
  4. 　酢酸鉛（II）三水和物、水溶性チタン錯体水溶液および水溶性ジルコニウム錯体水溶液を出発原料とする前駆体溶液に、水酸化ナトリウム水溶液および有機カルボン酸を混合した溶液を用いて加熱合成する工程を含むことを特徴とするナノ結晶の製造方法。 A step of heating and synthesizing a precursor solution starting from lead (II) acetate trihydrate, an aqueous solution of a water-soluble titanium complex and an aqueous solution of a water-soluble zirconium complex, using a solution obtained by mixing an aqueous solution of sodium hydroxide and an organic carboxylic acid. A method for producing a nanocrystal, comprising:
  5. 前記水溶性ジルコニウム錯体の配位子がヒドロキシカルボン酸であることを特徴とする請求項４に記載のナノ結晶の製造方法。 The method according to claim 4, wherein the ligand of the water-soluble zirconium complex is hydroxycarboxylic acid.
  6. 　酢酸鉛（II）三水和物に水酸化ナトリウム水溶液を添加した後、水溶性チタン錯体水溶液、アミン化合物、有機カルボン酸を混合した溶液を用いて加熱合成する工程を含むことを特徴とするナノ結晶の製造方法。 Nano-characteristics comprising a step of adding an aqueous solution of sodium hydroxide to lead (II) acetate trihydrate, and then performing a heat synthesis using a mixed solution of an aqueous solution of a water-soluble titanium complex, an amine compound, and an organic carboxylic acid. Method for producing crystals.
  7. 前記水溶性チタン錯体の配位子がヒドロキシカルボン酸であることを特徴とする請求項 ４～６のずれか一項に記載のナノ結晶の製造方法。 The method for producing nanocrystals according to any one of claims 4 to 6, wherein the ligand of the water-soluble titanium complex is hydroxycarboxylic acid.
  8. 前記有機カルボン酸がオレイン酸であることを特徴とする請求項４～７のいずれか一項に記載のナノ結晶の製造方法。 The method for producing nanocrystals according to any one of claims 4 to 7, wherein the organic carboxylic acid is oleic acid.
  9. 　前記水酸化ナトリウム水溶液の濃度が１ｍｏｌ／Ｌ以上１０ｍｏｌ／Ｌ以下であることを特徴とする請求項４～８のいずれか一項に記載のナノ結晶の製造方法。 The method for producing nanocrystals according to any one of claims 4 to 8, wherein the concentration of the aqueous sodium hydroxide solution is 1 mol / L or more and 10 mol / L or less.
  10. 　前記溶液において、鉛１モルに対する有機カルボン酸のモル数が１以上３０以下であることを特徴とする請求項４～９のいずれか一項に記載のナノ結晶の製造方法。 (10) The method for producing nanocrystals according to any one of (4) to (9), wherein the number of moles of the organic carboxylic acid per mole of lead is 1 or more and 30 or less in the solution.
  11. 　前記加熱を、１４０℃以上２９０℃以下の温度で実施することを特徴とする請求項４～１０のいずれか一項に記載のナノ結晶の製造方法。 11. The method for producing nanocrystals according to claim 4, wherein the heating is performed at a temperature of 140 ° C. or more and 290 ° C. or less.
  12. 　前記加熱を、１時間以上８０時間以下の時間で実施することを特徴とする請求項４～１０のいずれか一項に記載のナノ結晶の製造方法。 The method for producing nanocrystals according to any one of claims 4 to 10, wherein the heating is performed for a time of 1 hour to 80 hours.
  13. 　前記加熱を行った後の溶液を遠心分離する工程を有することを特徴とする請求項４～１０のいずれか一項に記載のナノ結晶の製造方法。 The method for producing nanocrystals according to any one of claims 4 to 10, further comprising a step of centrifuging the solution after the heating.
  14. 請求項１～３のいずれか一項に記載のナノ結晶を含む薄膜を有する電子デバイス。 An electronic device having a thin film containing the nanocrystal according to any one of claims 1 to 3.
  15. 請求項１～３のいずれか一項に記載のナノ結晶を含む薄膜と、該薄膜を挟むように設けられた一対の電極とを備えることを特徴とする圧電素子。 A piezoelectric element, comprising: a thin film containing the nanocrystal according to claim 1; and a pair of electrodes provided so as to sandwich the thin film.
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JPH08133738A (en) * 1994-11-04 1996-05-28 Ube Ind Ltd Production of pyroelectric crystal film
JPH11116395A (en) * 1997-10-20 1999-04-27 Ube Ind Ltd Precursor particle for complex titanium oxide
JP2010180103A (en) * 2009-02-06 2010-08-19 Ngk Insulators Ltd Method for producing membrane type element
JP2017048066A (en) * 2015-08-31 2017-03-09 国立研究開発法人産業技術総合研究所 Method for producing barium titanate zirconate nano crystals, and substrate coated with nanocrystal film
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