JP5025210B2 - Production method of dielectric material powder - Google Patents

Production method of dielectric material powder Download PDF

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JP5025210B2
JP5025210B2 JP2006262927A JP2006262927A JP5025210B2 JP 5025210 B2 JP5025210 B2 JP 5025210B2 JP 2006262927 A JP2006262927 A JP 2006262927A JP 2006262927 A JP2006262927 A JP 2006262927A JP 5025210 B2 JP5025210 B2 JP 5025210B2
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吉健 寺師
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Kyocera Corp
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本発明は、誘電体原料粉末の製法に関し、特に、誘電体粒子を母体として副成分の被膜を有する誘電体原料粉末の製法に関する。
The present invention relates to a dielectric material Powder manufacturing method, in particular, it relates to a dielectric material Powder manufacturing method having a sub-component of the coating of the dielectric particles as a matrix.

近年のセラミック電子部品は、電子機器の小型化に対応するため、小型高性能化が急速に進んでいる。積層セラミックコンデンサもまた同様であり、誘電体材料の高性能化と共に、誘電体層の薄層化、高積層化が進められている。これらの目標に対するアプローチとして、誘電体層を構成する原料粉末の配合、成形、焼成など種々の要素技術の開発が行われている。   In recent years, ceramic electronic components have been rapidly reduced in size and performance in order to cope with downsizing of electronic devices. The same applies to the multilayer ceramic capacitor, and the dielectric layer has been made thinner and higher in number as the dielectric material has higher performance. As an approach to these goals, various elemental technologies such as blending, forming and firing of raw material powders constituting the dielectric layer have been developed.

ところで、積層セラミックコンデンサは誘電体層と内部電極層とが交互に積層された構造を有し、その誘電体層は、通常、主成分であるチタン酸バリウムなどの主原料粉末と、この主原料粉末の誘電特性を制御するための希土類元素の酸化物等、各種の副原料粉末が添加された混合粉末の焼結体で構成される。   By the way, a multilayer ceramic capacitor has a structure in which dielectric layers and internal electrode layers are alternately laminated. The dielectric layer is usually composed of a main raw material powder such as barium titanate as a main component, and the main raw material. It consists of a sintered body of mixed powder to which various auxiliary raw material powders such as oxides of rare earth elements for controlling the dielectric properties of the powder are added.

そして、このような高性能の誘電体層を形成できる微粒のチタン酸バリウムを主成分とする誘電体原料粉末を得ようとする種々の開発が行われている。例えば、母体となるチタン酸バリウム粒子に対して副原料粉末となる添加剤をカップリング剤のかたちで添加してチタン酸バリウム粒子の表面に薄い被膜を形成することが提案されている（例えば、特許文献１参照）。
特開２００２−１９８２５１号公報 Various developments have been made to obtain a dielectric raw material powder mainly composed of fine barium titanate capable of forming such a high-performance dielectric layer. For example, it has been proposed to form a thin film on the surface of the barium titanate particles by adding an additive serving as an auxiliary material powder to the base barium titanate particles in the form of a coupling agent (for example, Patent Document 1).
JP 2002-198251 A

しかしながら、上述の特許文献１に開示されたチタン酸バリウムを主成分とする誘電体原料粉末は室温付近の温度で調製されているため、母体であるチタン酸バリウム粒子も高い表面エネルギを有する状態である。このため積層セラミックコンデンサ製品を製造する焼成の段階で被膜成分がチタン酸バリウム粒子に固溶しやすいことから、焼結後の誘電体磁器は被膜成分のチタン酸バリウム粒子内部への過剰な固溶により比誘電率が低下するという問題があった。   However, since the dielectric raw material powder mainly composed of barium titanate disclosed in Patent Document 1 is prepared at a temperature near room temperature, the base barium titanate particles also have a high surface energy. is there. For this reason, since the coating component is liable to be dissolved in the barium titanate particles at the firing stage of manufacturing the multilayer ceramic capacitor product, the sintered dielectric porcelain is excessively dissolved in the barium titanate particles inside the coating component. As a result, there is a problem that the relative dielectric constant is lowered.

従って本発明は、誘電体粒子の表面に被膜を有し、比誘電率の高い誘電体磁器を得ることのできる誘電体原料粉末の製法を提供することを目的とする。
Accordingly, the present invention has a coating film on the surface of the dielectric particles, and an object thereof is to provide a method end of the dielectric raw material powder capable of obtaining a high dielectric ceramic having a relative dielectric constant.

本発明の誘電体原料粉末の製法は、ペロブスカイト型結晶構造を有する誘電体粒子を、希土類元素と、Ｍｇ、Ｍｎ、Ｗ、Ｍｏ、ＶおよびＣｒのうち少なくとも１種の元素とを含む被膜成分とともに溶媒中で混合し、乾燥させて、前記誘電体粒子の表面に該誘電体粒子よりもサイズの小さい前記被膜成分が付着した複合粒子を調製する工程と、該複合粒子を構成している前記被膜成分を５００℃／ｓｅｃ以上の温度変化で加熱溶融させる加熱工程と、溶融した前記被膜成分を５００℃／ｓｅｃ以上の温度変化で冷却固化させることにより、前記誘電体粒子の断面の輪郭の９０％以上の領域に非晶質の被膜を形成する冷却工程とを有することを特徴とする。
The method for producing a dielectric raw material powder according to the present invention comprises a dielectric particle having a perovskite crystal structure, together with a coating component containing a rare earth element and at least one element selected from Mg, Mn, W, Mo, V and Cr. Mixing in a solvent and drying to prepare composite particles in which the coating component having a size smaller than that of the dielectric particles adheres to the surface of the dielectric particles; and the coating constituting the composite particles a heating step of heating and melting the components at a temperature change of more than 500 ° C. / sec, molten and then cooled and solidified at a temperature change of more than 500 ° C. / sec the coating components, 90% of the cross-sectional profile of the dielectric particles And a cooling step of forming an amorphous film in the above region.

上記誘電体原料粉末の製法では、前記加熱工程および前記冷却工程において、最高温度が１０００℃以上に設定された領域を有する炉心管内に、前記複合粒子を通過させることにより、前記複合粒子を１０００℃／ｓｅｃ以上の温度変化で加熱し、ひきつづき１０００℃／ｓｅｃ以上の温度変化で冷却すること、前記被膜成分として、平均粒子径が１０〜２０ｎｍの粒子を用いることが望ましい。
In the manufacturing method of the dielectric raw material powder, the composite particles are passed through a core tube having a region where the maximum temperature is set to 1000 ° C. or higher in the heating step and the cooling step, thereby allowing the composite particles to pass through 1000 ° C. It is desirable to heat at a temperature change of at least / sec and subsequently cool down at a temperature change of at least 1000 ° C./sec, and to use particles having an average particle size of 10 to 20 nm as the coating component.

本発明の誘電体原料粉末の製法は誘電体粒子と上述の複数の元素を含む被膜成分との複
合粒子を高い加熱の速度および冷却の速度を有する加熱炉に投入する方法であるため、母体である誘電体粒子を熱的に安定化でき、かつ誘電体粒子の表面に固溶し難い複数の元素を有する被膜を容易に形成することができる。そして、このような製法により得られた誘電体原料粉末は、母体である誘電体粒子の表面に副成分からなる被膜が非晶質の金属酸化物として強固に接着しており、被膜成分が非晶質に変化する程度まで加熱し冷却されているために、元の誘電体粒子や被膜成分が単独で存在する状態の場合に比較して表面エネルギが低い状態である。このように表面に非晶質の被膜を有する誘電体原料粉末では、誘電体原料粉末の表面エネルギが低いことから、焼成の段階で被膜成分が誘電体粒子に固溶し難くなる。このため誘電体粒子の内部に高誘電率の部分が多く残ることから、高誘電率の誘電体磁器を容易に得ることが可能となり、高容量かつ高絶縁性の積層セラミックコンデンサを得ることができる。
 The method for producing a dielectric raw material powder of the present invention is a method in which composite particles of dielectric particles and a coating component containing a plurality of elements described above are put into a heating furnace having a high heating rate and a cooling rate. A dielectric particle can be thermally stabilized, and a film having a plurality of elements that are difficult to dissolve in the surface of the dielectric particle can be easily formed. In the dielectric raw material powder obtained by such a manufacturing method, the coating composed of subcomponents is firmly adhered as an amorphous metal oxide to the surface of the base dielectric particles, and the coating component is non-coated. Since it is heated and cooled to such an extent that it changes to crystalline, the surface energy is lower than in the case where the original dielectric particles and coating components exist alone. Thus, in the dielectric raw material powder having an amorphous coating on the surface, the surface energy of the dielectric raw material powder is low, so that the coating component hardly dissolves in the dielectric particles at the firing stage. For this reason, since a large portion of the high dielectric constant remains in the dielectric particles, it is possible to easily obtain a dielectric ceramic having a high dielectric constant, and to obtain a multilayer ceramic capacitor having a high capacity and high insulation. .

図１は、誘電体原料粉末の断面の透過電子顕微鏡写真である。図２は、この透過電子顕微鏡写真の誘電体原料粉末の模式図である。図１および図２において、１は誘電体粒子、３は被膜である。本発明により作製された誘電体原料粉末は、誘電体粒子１の表面に形成された被膜３を有し、その被膜３が非晶質の金属酸化物であり、特に、該被膜が、希土類元素と、Ｍｇ、Ｍｎ、Ｗ、Ｍｏ、ＶおよびＣｒのうち少なくとも１種の元素とを含有する非晶質の金属酸化物である。また、被膜３は誘電体粒子１の表面の全面に形成されている。ここで、誘電体粒子１の表面の全面とは、図１に示した透過電子顕微鏡写真のように、誘電体原料粉末の断面を観察したときに、被膜３が誘電体粒子１の輪郭の９０％以上の周囲に形成されていることを意味する。
Figure 1 is a transmission electron micrograph of a cross section of Yuden material powder. FIG. 2 is a schematic diagram of the dielectric material powder in the transmission electron micrograph. In FIG. 1 and FIG. 2, 1 is a dielectric particle, 3 is a film. The dielectric raw material powder produced according to the present invention has a coating 3 formed on the surface of the dielectric particles 1, and the coating 3 is an amorphous metal oxide . If, Mg, Mn, W, Mo , Ru amorphous metal oxide der containing at least one element of V and Cr. Further, the film 3 is formed on the entire surface of the dielectric particles 1. Here, the entire surface of the dielectric particles 1, as the transmission electron micrograph shown in FIG. 1, when observing the cross section of the Yuden material powder, the film 3 of the outline of the dielectric particles 1 It means that it is formed around 90% or more.

また、誘電体粒子１とは、一般式がＡＢＯ３で表され、ペロブスカイト型結晶構造を有する誘電体粒子１のことであり、チタン酸バリウム（ＢａＴｉＯ３：ＢＴ）、チタン酸ストロンチウム（ＳｒＴｉＯ３：ＳＴ）、チタン酸カルシウム（ＣａＴｉＯ３：ＣＴ）に代表されるものである。この場合、室温付近における比誘電率が最も高いという点でチタン酸バリウムを主成分とするものが好ましい。 The dielectric particle 1 is a dielectric particle 1 having a general formula represented by ABO 3 and having a perovskite crystal structure. Barium titanate (BaTiO 3 : BT), strontium titanate (SrTiO 3 : ST), represented by calcium titanate (CaTiO 3 : CT). In this case, those having barium titanate as the main component are preferable in that they have the highest relative dielectric constant near room temperature.

また、誘電体原料粉末の平均粒子径は１００〜１５０ｎｍであることが望ましい。平均粒子径が１００ｎｍ以上であると、誘電体粒子１に対する被膜３成分の拡散領域の割合が小さくなり、被膜３によって誘電体原料粉末がコアシェル構造となる場合に、コア部の割合が大きくなることから、微粒であっても高い比誘電率を得ることが可能となる。
 Further, it is preferable average particle diameter of Yuden material powder is 100 to 150 nm. When the average particle diameter is 100 nm or more, the ratio of the diffusion region of the coating 3 component to the dielectric particles 1 decreases, and when the dielectric material powder has a core-shell structure by the coating 3, the ratio of the core portion increases. Therefore, it is possible to obtain a high relative dielectric constant even with fine particles.

一方、平均粒子径が１５０ｎｍ以下であると、例えば、積層セラミックコンデンサの誘電体層として薄層化に好適なものとなり、誘電体層中において厚み方向に多くの粒界を形成できるため高絶縁性となる。なお、焼結体における結晶粒子の平均粒子径は９０〜１４０ｎｍであることが望ましい。この場合、焼結体中における結晶粒子のサイズは、その結晶粒子の最大径の部分の断面ではないため、元の誘電体原料粉末のサイズよりも小さくな
る。
On the other hand, when the average particle size is 150 nm or less, for example, the dielectric layer of the multilayer ceramic capacitor is suitable for thinning, and since many grain boundaries can be formed in the thickness direction in the dielectric layer, high insulating properties are achieved. It becomes. The average particle diameter of the crystal grains in the sintered body is preferably a 90～140Nm. In this case, since the size of the crystal particles in the sintered body is not the cross section of the maximum diameter portion of the crystal particles, it is smaller than the size of the original dielectric material powder.

また、誘電体原料粉末を構成する被膜３の厚みは１．４〜２ｎｍであることが望ましい。被膜３の厚みが１．４ｎｍ以上であると誘電体粒子１の表面の全面に、ほぼ均一な被膜３が形成されやすくなり、誘電体粒子１の表面の全面における被膜３の成分の効果の均一化が図れる。
It is also desirable thickness of the coating 3 of the Yuden material powder is 1.4～2Nm. When the thickness of the coating 3 is 1.4 nm or more, a substantially uniform coating 3 is easily formed on the entire surface of the dielectric particles 1, and the effect of the components of the coating 3 on the entire surface of the dielectric particles 1 is uniform. Can be achieved.

また、誘電体原料粉末の粒子径のばらつき（ＣＶ：平均粒子径をｘ、標準偏差をσとしたときに、σ／ｘ（％）で表される。）を小さくできるという利点がある。この場合、ＣＶは積層セラミックコンデンサの高温負荷寿命を高めるという理由から６０％以下が好ましい。
Also, variation in particle element diameter of the dielectric material powder (CV: an average particle child size x, when the standard deviation sigma, represented by σ / x (%).) There is an advantage that can be reduced . In this case, the CV is preferably 60% or less because it increases the high temperature load life of the multilayer ceramic capacitor.

一方、被膜３の厚みが２ｎｍ以下であると、被膜３の厚みによる誘電体原料粉末の粒子径の増加を抑制できるとともにＣＶが小さくなり、誘電体粒子１への被膜３成分の固溶量を低減でき、誘電体原料粉末を高誘電率化できるという利点がある。   On the other hand, when the thickness of the coating 3 is 2 nm or less, an increase in the particle diameter of the dielectric raw material powder due to the thickness of the coating 3 can be suppressed and the CV becomes small, so that the solid solution amount of the coating 3 component in the dielectric particles 1 can be reduced. There is an advantage that the dielectric material powder can be reduced and the dielectric constant of the dielectric material powder can be increased.

一方、被膜３が非晶質でないような状態では、誘電体粒子１の表面に強固にかつ厚みのばらつきの少ない状態で強固に固着させることは困難であり、例えば、被膜成分の錯体や溶液を用いて、１０００℃以上の高温での加熱を行うことなく、例えば、室温付近の温度、もしくは５００℃以下の温度で熱処理された誘電体原料粉末などは原料粉末の混合やスラリ調合時に形成された被膜３が剥がれやすくなり、被膜３は透過電子顕微鏡観察結果によれば格子模様が見られ、あたかも結晶化しているような状態であり、このように被膜３が結晶化しているように見える状態であれば誘電体粒子１の表面の全面に広がらずに分離した状態で形成されている。このため誘電体原料粉末の焼結性にばらつきが発生しやすくなる。   On the other hand, in a state where the coating 3 is not amorphous, it is difficult to firmly adhere to the surface of the dielectric particles 1 with little variation in thickness. For example, a dielectric raw material powder that has been heat-treated at a temperature near room temperature or a temperature of 500 ° C. or lower without being heated at a high temperature of 1000 ° C. or higher is formed during mixing of raw material powders or slurry preparation. According to the observation result of the transmission electron microscope, the coating film 3 is easily peeled off, and a lattice pattern is seen. If present, the dielectric particles 1 are formed in a separated state without spreading over the entire surface. For this reason, the sinterability of the dielectric material powder tends to vary.

なお、本発明において非晶質というのは、透過電子顕微鏡写真から格子模様が見られないものとする。また、非晶質か否かの判定は、透過電子顕微鏡に付設の電子線回折によっても評価できる。この場合、格子列が乱れて、格子点間隔が不規則かつ格子点角度が一定でない状態を非晶質とする。
Incidentally, because the amorphous Te present invention odor shall not lattice pattern is observed from the transmission electron micrographs. The determination of whether amorphous or not can be evaluated by electron diffraction attached to a transmission electron microscope. In this case, a state in which lattice rows are disordered, lattice point intervals are irregular, and lattice point angles are not constant is defined as amorphous .

また、本発明における被膜３は希土類元素を主成分とするものであるが、この場合、希土類元素の酸化物はＡＢＯ３で表されるチタン酸バリウム、チタン酸ストロンチウムまたはチタン酸カルシウムなどの誘電体材料に比較して高融点であるために、ペロブスカイト型の誘電体粒子１を熱的に安定化できる。また、希土類元素が酸化物として誘電体粒子１に微量固溶すると誘電体原料粉末の絶縁性が高まり高温負荷寿命等の信頼性を高められるという利点がある。この場合、上記の効果が有する点で、特にＹおよびその酸化物が好ましい。
Further, the film 3 definitive to the onset bright is as a main component a rare earth element, in this case, oxides of rare earth elements barium titanate expressed by ABO 3, such as strontium titanate or calcium titanate Since the melting point is higher than that of the dielectric material, the perovskite type dielectric particles 1 can be thermally stabilized. Further, when a rare earth element is dissolved in the dielectric particles 1 as a small amount of oxide as an oxide, there is an advantage that the insulating property of the dielectric raw material powder is increased and the reliability such as high temperature load life can be improved. In this case, Y and its oxide are particularly preferable in view of the above effects.

また、本発明の被膜３では、希土類元素とともに、Ｍｇ、Ｍｎ、Ｗ、Ｍｏ、ＶおよびＣｒのうち少なくとも１種の元素を含有するものである。
In addition, the coating 3 of the present invention contains at least one element of Mg, Mn, W, Mo, V and Cr together with the rare earth element.

これらの元素のうち、Ｍｎ、Ｃｒ、ＭｏおよびＷは誘電体粉末の耐還元性を高めるという点で好ましいものであり、またＭｇおよびＶはチタン酸バリウムなどの誘電体粉末に固溶することにより絶縁性を高め、かつ比誘電率の温度依存性を小さくできるという利点がある。
Of these elements, Mn, Cr, Mo and W are those preferred from the viewpoint of increasing the reduction resistant dielectric powder and Mg and V by solid solution the dielectric powder such as barium titanate there is an advantage that the insulating property can be reduced temperature dependence of the high-order, and the dielectric constant.

被膜３の厚みは、透過電子顕微鏡写真から求められ、誘電体粒子１の周囲を等間隔に４箇所指定して測定した厚みの平均である。この場合、上記のように格子列が乱れた領域を非晶質の金属酸化物である被膜３とする。
The thickness of the film 3 is determined from transmission electron micrographs, Ru average der thickness measured by specifying four places around the dielectric particles 1 at regular intervals. In this case, you the region disordered lattice columns as above Symbol a film 3 which is an amorphous metal oxide.

図３は、熱機械分析（ＴＭＡ）を用いて得られた誘電体原料粉末の成形体の熱収縮曲線の模式図である。熱収縮曲線Ａは本発明によって得られた誘電体原料粉末の場合であり、熱収縮曲線Ｂは液相法によって誘電体粒子１の表面に被膜成分を単に付着させ、５００℃で熱処理しただけの誘電体原料粉末の場合である。これら熱収縮曲線Ａ、Ｂを示す誘電体原料粉末に含まれる元素は、ともにＹ、ＭｇおよびＭｎである。
FIG. 3 is a schematic diagram of a heat shrinkage curve of a molded body of dielectric raw material powder obtained using thermomechanical analysis (TMA). The heat shrinkage curve A is the case of the dielectric raw material powder obtained by the present invention, and the heat shrinkage curve B is obtained by simply attaching the coating component to the surface of the dielectric particles 1 by the liquid phase method and heat-treating at 500 ° C. This is the case of the dielectric material powder. The elements contained in the dielectric material powder showing these heat shrink curves A and B are all Y, Mg and Mn.

本発明によって得られる誘電体原料粉末は、被膜成分と共に高温にて加熱されているために、誘電体粒子１の表面に被膜成分を単に付着させただけの誘電体原料粉末に比較して焼結開始温度が高温側に移動し、かつ収縮率の大きいものとなる。この結果から、本発明の誘電体原料粉末は誘電体粒子１の表面に被膜成分を単に付着させただけの誘電体原料粉末に比較して焼結性に優れたものとなる。焼結開始温度は熱収縮曲線が大きく折れ曲がる
曲線の交点Ｓとする。
Since the dielectric raw material powder obtained by the present invention is heated at a high temperature together with the coating component, it is sintered as compared with the dielectric raw material powder in which the coating component is simply adhered to the surface of the dielectric particles 1. The starting temperature moves to the high temperature side and the shrinkage rate is large. From this result, the dielectric raw material powder of the present invention has superior sinterability compared to the dielectric raw material powder in which the coating component is simply adhered to the surface of the dielectric particles 1. The sintering start temperature is an intersection S of curves where the heat shrinkage curve is greatly bent.

次に、本発明の誘電体原料粉末の製法について説明する。図４は、本発明の誘電体原料粉末の製法に用いる複合粒子の模式図である。本発明では、まず母体となるペロブスカイト型構造を有する誘電体粒子１を準備する。ここで用いる誘電体粒子１については、例えば、一般式がＡＢＯ３で表されるＢａＴｉＯ３の場合、バリウムとチタンの原子比（Ｂａ／Ｔｉ）は０．９９７〜１．００５の範囲であることが望ましい。（Ｂａ／Ｔｉ）が０．９９７〜１．００５の範囲であると、正方晶を示すペロブスカイト型構造を有する均質な誘電体粒子を形成できるという利点がある。
Next, a method for producing the dielectric material powder of the present invention will be described. FIG. 4 is a schematic view of composite particles used in the method for producing a dielectric material powder of the present invention. In the present invention, first, dielectric particles 1 having a perovskite structure as a base are prepared. For the dielectric particles 1 used here, for example, when the general formula is BaTiO 3 represented by ABO 3 , the atomic ratio (Ba / Ti) of barium to titanium is in the range of 0.997 to 1.005. Is desirable. When (Ba / Ti) is in the range of 0.997 to 1.005, there is an advantage that homogeneous dielectric particles having a perovskite structure showing tetragonal crystals can be formed.

また、本発明の誘電体原料粉末の製法に用いる誘電体粒子１としては、微粒かつ高結晶性であることが望ましく、この点で固相法、ゾルーゲル法、水熱法、蓚酸塩法または噴霧法のいずれかの製法で調製される誘電体粒子１が好適である。この中で、微粒化を可能とする点で水熱法が好ましく、また、原料中の炭酸基や水酸基を低減できるという点で固相法が望ましい。   The dielectric particles 1 used in the method for producing the dielectric raw material powder of the present invention are preferably fine and highly crystalline. In this respect, the solid phase method, the sol-gel method, the hydrothermal method, the oxalate method, or the spraying method is preferable. Dielectric particles 1 prepared by any of the methods are suitable. Among these, the hydrothermal method is preferable from the viewpoint of enabling atomization, and the solid phase method is preferable from the viewpoint that carbonic acid groups and hydroxyl groups in the raw material can be reduced.

また、本発明の誘電体原料粉末の製法に用いる誘電体粒子１の平均粒子径は１００〜１５０ｎｍであることが望ましい。用いる誘電体粒子１の平均粒子径が１００〜１５０ｎｍであると、微粒化による誘電体層の薄層化および高絶縁化が図れるという利点がある。   Moreover, it is desirable that the average particle diameter of the dielectric particles 1 used in the production method of the dielectric material powder of the present invention is 100 to 150 nm. When the average particle diameter of the dielectric particles 1 to be used is 100 to 150 nm, there is an advantage that the dielectric layer can be thinned and highly insulated by atomization.

そして、本発明の誘電体原料粉末の製法は、誘電体粒子１を、希土類元素と、Ｍｇ、Ｍｎ、Ｗ、Ｍｏ、ＶおよびＣｒのうち少なくとも１種の元素とを含む被膜成分７とともに溶媒中で混合し、乾燥させて、誘電体粒子１の表面に、この誘電体粒子１よりもサイズの小さい被膜成分７が付着した複合粒子５を調製することを特徴とする。
The preparation of the dielectric material powder of the present invention, both the solvent dielectric particles 1, and rare earth elements, Mg, Mn, W, Mo, a film component 7 and at least one element of V and Cr The composite particles 5 are prepared by mixing them in the inside and drying to prepare the composite particles 5 to which the coating component 7 having a smaller size than the dielectric particles 1 adheres to the surface of the dielectric particles 1.

この場合、希土類元素およびＭｇは硝酸塩を用いること、Ｍｎは酢酸塩を用いることが好ましい。硝酸塩や酢酸塩は高い溶解性を有しているためイオン濃度を調整しやすい。   In this case, nitrates are preferably used for the rare earth elements and Mg, and acetates are preferably used for Mn. Since nitrates and acetates have high solubility, it is easy to adjust the ion concentration.

ここで、誘電体粒子１よりもサイズの小さい被膜成分が付着した複合粒子５では、この複合粒子５を構成する被膜成分７が液状またはスラリなどの場合、図４に示すように誘電体粒子１の表面に部分的に膜のように接着されている場合や液体が表面張力によって球状化して接着している場合など種々の状態で付着している。なお、このような付着の状態は被膜成分７の相の状態や粘度などによって異なる。通常、複合粒子５の状態では誘電体粒子１の表面に被膜成分７がファンデアワールス力等によって付着した状態であり、また、被膜成分７が誘電体粒子１の表面に局所的に存在しているため、被膜成分７の厚みが不均一であり、また、被膜成分７を酸化物の粉末のかたちで用いたものは、透過電子顕微鏡観察結果によれば格子模様が見られる。そのため本発明では、このように透過電子顕微鏡観察結果により格子模様が見られる状態を結晶質の状態であるとする。   Here, in the composite particle 5 to which the coating component having a size smaller than that of the dielectric particle 1 is adhered, when the coating component 7 constituting the composite particle 5 is liquid or slurry, the dielectric particle 1 as shown in FIG. It adheres in various states, such as when it is partially adhered to the surface of the film like a film, or when the liquid is spheroidized by surface tension. Such an adhesion state varies depending on the phase state and viscosity of the coating component 7. Usually, in the state of the composite particle 5, the coating component 7 is attached to the surface of the dielectric particle 1 by van der Waals force or the like, and the coating component 7 exists locally on the surface of the dielectric particle 1. Therefore, the thickness of the coating component 7 is non-uniform, and when the coating component 7 is used in the form of an oxide powder, a lattice pattern is observed according to the observation result of the transmission electron microscope. Therefore, in the present invention, it is assumed that the state in which the lattice pattern is seen based on the observation result of the transmission electron microscope is the crystalline state.

本発明の製法においては、被膜成分７として、上述のように、その特性に合わせて種々のセラミック成分を用いることができ、これらの元素は錯体、溶液または酸化物粉末などの原料を用いることが可能である。
In the production method of the present invention, as a film component 7, as described above, it is possible to use various ceramic component in accordance with the characteristics thereof, these elements can be used complex, a solution or an oxide powder of any material Is possible.

被膜成分７として、上記各元素の酸化物粉末を用いる場合、平均粒子径が１０〜２０ｎｍの粒子を用いることが望ましい。平均粒子径が１０〜２０ｎｍであると被膜成分７による複合粒子５の粒子径のばらつきを抑制できるという利点がある。そして、被膜成分７を酸化物粉末のかたちで添加する場合、母体である誘電体粒子１の表面に形成される被膜３
の厚みをより均一にするという点で、誘電体粒子１の平均粒子径よりも小さいことが重要であり、この場合、誘電体粒子１の平均粒子径に対して５０分の１以下の大きさがより好ましい。
When the oxide powder of each element is used as the coating component 7, it is desirable to use particles having an average particle diameter of 10 to 20 nm. There is an advantage that the average particle diameter can suppress the variation of the particle element size of the composite particles 5 by coating component 7 When it is: 10 to 20 nm. When the coating component 7 is added in the form of an oxide powder, the coating 3 formed on the surface of the dielectric particles 1 as the base material.
It is important that the thickness of the dielectric particles 1 is smaller than the average particle diameter of the dielectric particles 1, and in this case, the size is 1/50 or less of the average particle diameter of the dielectric particles 1. Is more preferable.

以下、被膜成分７の形成工程について説明する。本発明の製法においては、上述のように、被膜成分７は母体となる誘電体粒子１に対して均一に混合できるという点では錯体や溶液が好ましい。一方、Ｙなど希土類元素など上記各元素の酸化物粉末を用いると、錯体から発生する遊離成分を低減でき、回収される誘電体原料粉末中への混入を低減でき、被膜３を高純度化できるという利点がある。   Hereinafter, the formation process of the film component 7 will be described. In the production method of the present invention, as described above, a complex or a solution is preferable in that the coating component 7 can be uniformly mixed with the dielectric particles 1 as a base. On the other hand, when oxide powders of the above-mentioned elements such as rare earth elements such as Y are used, free components generated from the complex can be reduced, contamination in the recovered dielectric material powder can be reduced, and the coating 3 can be highly purified. There is an advantage.

次に、誘電体粒子１と上記した被膜成分７とを溶媒中で混合する。この場合、溶媒としては、被膜成分７の溶解性や加熱による発火を考慮して水が好ましいが、低分子量の有機溶媒でもよい。本発明の製法において添加する被膜成分７の量は母体となる誘電体粒子１の表面に形成する被膜３の厚みに応じて調整される。   Next, the dielectric particles 1 and the coating component 7 described above are mixed in a solvent. In this case, the solvent is preferably water in consideration of solubility of the coating component 7 and ignition by heating, but may be a low molecular weight organic solvent. The amount of the coating component 7 added in the production method of the present invention is adjusted in accordance with the thickness of the coating 3 formed on the surface of the dielectric particles 1 serving as a base.

次に、上記誘電体粒子１と被膜成分７との混合溶液を乾燥させて、誘電体粒子１と被膜成分７との複合粒子５を調製する。乾燥温度は得られる複合粒子５の凝集を抑制するという点で用いた溶媒が揮発する程度の室温より少し高い温度、例えば、８０〜１４０℃の温度が好ましい。乾燥は常圧での加熱乾燥、真空乾燥、スラリのスプレードライ等の方法を適用することができ、低温での乾燥が行えるという点で真空乾燥が好ましい。また、被膜成分を溶液から形成する場合には、スラリから金属成分が溶解していた溶媒を揮発でき凝集を抑制できるという点でスプレードライが好ましい。   Next, the mixed solution of the dielectric particles 1 and the coating component 7 is dried to prepare composite particles 5 of the dielectric particles 1 and the coating component 7. The drying temperature is preferably a temperature slightly higher than room temperature, such as 80 to 140 ° C., at which the solvent used in terms of suppressing aggregation of the resulting composite particles 5 is volatilized. Drying can be performed by methods such as heat drying at normal pressure, vacuum drying, spray drying of slurry, etc., and vacuum drying is preferable in that drying at low temperature can be performed. Further, when the coating component is formed from a solution, spray drying is preferable because the solvent in which the metal component is dissolved from the slurry can be volatilized and aggregation can be suppressed.

次に、得られた複合粒子５を加熱炉に投入して誘電体粒子１の表面に付着させた被膜成分７を非晶質に変化させつつ誘電体粒子１の表面に固着させる。   Next, the obtained composite particle 5 is put into a heating furnace, and the coating component 7 adhered to the surface of the dielectric particle 1 is fixed to the surface of the dielectric particle 1 while being changed to amorphous.

図５は、本発明の誘電体原料粉末を作製するための加熱炉の断面模式図である。用いる加熱炉では、炉本体１１の上部に原料投入フィーダ１３が、一方、炉本体１１の下部に粉末回収部１５が備えられており、さらに、回収部１５には炉心管１７内の気流の流れ（層流）をつくるための吸引装置２１が備えられている。炉本体１１では炉心管１７の周囲に加熱部１９が設けられている。そして、加熱炉では、原料投入フィーダ１３から炉本体１１を通じて粉末回収部１５に至る経路（矢印）の方向に向けて吸引したガスによって、複合粒子５を含む気体の流れが形成される。また、炉本体１１には、内部に複合粒子５を含む気体が流れる炉心管１７の長さ方向の中央部に、高温に設定された温度領域の空間２３が設けられており、本発明においては、上述の複合粒子５を構成している被膜成分７を５００℃／ｓｅｃ以上の温度変化で加熱溶融させる加熱工程と、溶融した前記被膜成分を５００℃／ｓｅｃ以上の温度変化で冷却固化させる冷却工程とを有することを特徴とする。
FIG. 5 is a schematic cross-sectional view of a heating furnace for producing the dielectric material powder of the present invention. In the heating furnace to be used, the raw material charging feeder 13 is provided at the upper part of the furnace main body 11, while the powder recovery unit 15 is provided at the lower part of the furnace main body 11, and the flow of the airflow in the furnace core tube 17 is further provided in the recovery unit 15. A suction device 21 for producing (laminar flow) is provided. In the furnace body 11, a heating unit 19 is provided around the furnace core tube 17. In the heating furnace, a gas flow containing the composite particles 5 is formed by the gas sucked in the direction of the path (arrow) from the raw material charging feeder 13 to the powder recovery unit 15 through the furnace body 11. Further, the furnace body 11 is provided with a space 23 in a temperature region set at a high temperature at the center in the length direction of the furnace core tube 17 through which the gas containing the composite particles 5 flows. , A heating step in which the coating component 7 constituting the composite particle 5 is heated and melted at a temperature change of 500 ° C./sec or more, and cooling in which the melted coating component is cooled and solidified at a temperature change of 500 ° C./sec or more. And a process.

そして、本発明における加熱工程は、上記複合粒子５を、温度が上昇する方向に変化する温度勾配を有し最高温度が１０００℃以上に設定された空間２３を、この複合粒子５の周囲の温度が１０００℃／ｓｅｃ以上で変化するように通過させることが望ましい。   In the heating step in the present invention, a space 23 having a temperature gradient that changes the temperature of the composite particle 5 in the direction in which the temperature rises and a maximum temperature set to 1000 ° C. or higher is set to a temperature around the composite particle 5. It is desirable to pass through so that the temperature changes at 1000 ° C./sec or more.

また、上記の加熱工程に続く冷却工程は、複合粒子５を、最高温度が１０００℃以上に設定された空間２３から温度が低下する方向に変化する温度勾配を有する空間２４を、この複合粒子５の周囲の温度が１０００℃／ｓｅｃ以上で変化するように通過させることが望ましい。   In the cooling step subsequent to the heating step, the composite particle 5 is converted into a space 24 having a temperature gradient that changes in a direction in which the temperature decreases from the space 23 in which the maximum temperature is set to 1000 ° C. or higher. It is desirable to pass through so that the ambient temperature of the liquid crystal changes at 1000 ° C./sec or more.

本発明では、被膜成分７が溶融する温度領域である空間２３の温度は得られる誘電体原料粉末の粒子径のばらつき（ＣＶ）を小さくするという点で、特に１１００℃以上１
２５０℃以下が好ましい。加熱炉の最高温度が１０００℃以上であると、誘電体粒子１の表面において被膜成分７が溶解し濡れ広がりやすいという利点がある。
In the present invention, in that the coating component 7 to reduce variations in the particle element diameter of the dielectric material powder temperature is obtained in the space 23 is a temperature range for melting (CV), in particular 1100 ° C. or higher 1
250 degrees C or less is preferable. When the maximum temperature of the heating furnace is 1000 ° C. or higher, there is an advantage that the coating component 7 is easily dissolved and spreads on the surface of the dielectric particles 1.

上述のように本発明の製法では複合粒子５を上記のような方法で加熱し冷却することにより、誘電体粒子１の表面に付着した被膜成分７を非晶質に変化させることができる。
As described above in the process of the present invention is by pressurized heated cooling in composite particles 5, such as of the above method, it is possible to change the coating component 7 adhering to the surface of the dielectric particles 1 to amorphous.

上述の加熱工程および冷却工程の条件は、複合粒子５を含む気体の流れの速度と、加熱炉における炉心管１７の上下端と最高温度との温度差と、炉心管１７の上下端と炉心管１７の最高温度を示す位置との間の距離とから求められる。
The conditions of the heating process and the cooling process described above are the flow rate of the gas containing the composite particles 5, the temperature difference between the upper and lower ends of the core tube 17 and the maximum temperature in the heating furnace, the upper and lower ends of the core tube 17 and the core tube. It is calculated | required from the distance between the position which shows the maximum temperature of 17 .

なお、本発明の製法においては加熱炉の炉心管１７の下端部側から吸引して層流を形成しているために炉心管１７を境に上端部側と下端部側とは複合粒子５を通過させる周囲の温度変化はほぼ同じになる。   In the production method of the present invention, since the laminar flow is formed by suction from the lower end side of the core tube 17 of the heating furnace, the upper end side and the lower end side of the core tube 17 are the composite particles 5. The ambient temperature change to pass through is almost the same.

さらに、誘電体粒子１の表面上での被膜成分７の凝集や結晶化を抑制し、得られる誘電
体原料粉末の粒子径のばらつき（ＣＶ）を低減するという理由から、本発明では以下のような温度変化を有する環境に設定することが望ましい。
Further, to suppress the agglomeration or crystallization of the coating components 7 on the surface of the dielectric particles 1, for reasons of reducing the variation of the particle element diameter of the dielectric material powder obtained (CV), in the present invention the following It is desirable to set the environment having such a temperature change.

つまり、本発明では、複合粒子５を構成している被膜成分７を溶融させる加熱工程において、複合粒子５を通過させる周囲の温度変化が１０００℃／ｓｅｃ以上、特に、１１００℃／ｓｅｃ以上が好ましい。
That is, in the present invention, in the heating step of the coating component 7 melting constituting the composite particles 5, the composite ambient temperature changes passing the particles 5 1000 ° C. / sec or more, particularly, not less than 1100 ° C. / sec preferable.

また、上記の加熱工程の後の被膜成分７を固化させる冷却工程においても、加熱工程と同様に、複合粒子５を通過させる周囲の温度変化が１０００℃／ｓｅｃ以上、特に、１１００℃／ｓｅｃ以上が好ましい。複合粒子５を通過させる周囲の温度変化が１１００℃／ｓｅｃ以上であると、複合粒子５の表面に付着した被膜成分７が非晶質に変化しやすく、また、被膜３の厚みのばらつきを小さくでき、これから得られる誘電体原料粉末の粒子径のばらつき（ＣＶ）を低減できるという利点がある。 Also in the cooling step of the solid of the coating composition 7 after the heating step, as in the heating step, the ambient temperature change passing the composite particles 5 1000 ° C. / sec or more, in particular, 1100 ° C. / sec The above is preferable. If the ambient temperature change through which the composite particle 5 passes is 1100 ° C./sec or more, the coating component 7 attached to the surface of the composite particle 5 is likely to change to amorphous, and the variation in the thickness of the coating 3 is reduced. There is an advantage that variation in the particle diameter (CV) of the dielectric material powder obtained therefrom can be reduced.

一方、加熱工程および冷却工程において複合粒子５を通過させる条件（温度変化）が２６００℃／ｓｅｃ以下では被膜成分７の未反応物量を低減でき、例えば、被膜成分７として希土類元素の酸化物粉末を用いた場合に被膜３の結晶化を抑制できる。   On the other hand, when the condition (temperature change) for allowing the composite particles 5 to pass through in the heating step and the cooling step is 2600 ° C./sec or less, the amount of unreacted material of the coating component 7 can be reduced. When used, crystallization of the coating 3 can be suppressed.

本発明では、誘電体粒子１の表面において被膜成分の少なくとも一部が非晶質の被膜３に変化している複合粒子５を、加熱炉に複数回通過させて加熱することが好ましい。これにより融点の異なる複数の元素の酸化物を誘電体粒子１の表面において強固に固着させることが可能となる。   In the present invention, it is preferable that the composite particles 5 in which at least a part of the coating component is changed to the amorphous coating 3 on the surface of the dielectric particles 1 are passed through a heating furnace several times and heated. This makes it possible to firmly fix oxides of a plurality of elements having different melting points on the surface of the dielectric particles 1.

なお、本発明では炉心管１７の下端部側から空気を吸引する方法であるために加熱工程および冷却工程において複合粒子５を通過させる条件（温度変化）は同じである。   In the present invention, since air is sucked from the lower end side of the core tube 17, the conditions (temperature change) for allowing the composite particles 5 to pass in the heating step and the cooling step are the same.

これに対して、自然落下のように吸引操作を行わずに複合粒子５を加熱および冷却した場合には複合粒子５が加熱炉の炉心管１１の中で落下中に凝集して粗大な粒子が形成されてしまう。なお、加熱工程および冷却工程において複合粒子５を通過させる条件（温度勾配）を上記のように設定でき、本発明のように誘電体粒子１の表面に非晶質の被膜３を形成できるという点で、炉心管１７の長さは３ｍ以上、特に、４ｍ以上が好ましい。   On the other hand, when the composite particles 5 are heated and cooled without performing a suction operation as in natural fall, the composite particles 5 aggregate in the core tube 11 of the heating furnace and fall into coarse particles. Will be formed. In addition, the conditions (temperature gradient) for allowing the composite particles 5 to pass in the heating step and the cooling step can be set as described above, and the amorphous coating 3 can be formed on the surfaces of the dielectric particles 1 as in the present invention. Thus, the length of the core tube 17 is preferably 3 m or more, particularly preferably 4 m or more.

なお、本発明の製法は誘電体以外のセラミック粉末についても被膜を形成する手法として適用できることはいうまでもなく、例えば、チタンジルコン酸鉛、アルミナ、ジルコニア、コーディエライト、ムライト、スピネル等のセラミック粉末や種々のガラス粉末等にも適用可能である。   In addition, it cannot be overemphasized that the manufacturing method of this invention is applicable as a method of forming a film also about ceramic powders other than a dielectric material, for example, ceramics, such as lead zirconate titanium, alumina, zirconia, cordierite, mullite, spinel, etc. It can also be applied to powder and various glass powders.

本発明の製法は、従来より公知の製法である、元素を含む溶液を加熱炉中に噴霧して溶液からセラミック粉末を合成する噴霧熱分解法に比較して、母体として緻密な誘電体粒子１をそのまま用いることから、加熱処理後も緻密な誘電体原料粉末が得られる。それととともに、母体である誘電体粒子１の表面に被膜３を形成でき、しかも上記した被膜成分７の混合と加熱を繰り返し行うことにより、誘電体粒子１の表面に被膜３を層状に形成できるという利点を有する。   Compared with the spray pyrolysis method in which the ceramic powder is synthesized from a solution by spraying a solution containing an element in a heating furnace, which is a conventionally known method, the production method of the present invention is a dense dielectric particle 1. Is used as it is, a dense dielectric material powder can be obtained even after heat treatment. At the same time, the coating film 3 can be formed on the surface of the dielectric particle 1 as a base, and the coating film 7 can be formed in a layered manner on the surface of the dielectric particle 1 by repeatedly mixing and heating the coating component 7 described above. Have advantages.

つまり、噴霧熱分解法は合成時に溶媒の揮発とセラミックスの合成が同時に起こるために、合成されるセラミック粉末が溶媒の揮発により膨らみ、得られる粉末がいびつな形状であったり、セラミック粉末の内部に空隙が生じやすい。しかも、本発明の製法のように誘電体粒子１の表面に層状に被膜３を形成することができない。   In other words, since the solvent vaporization and ceramic synthesis occur simultaneously during the spray pyrolysis method, the ceramic powder to be synthesized swells due to the volatilization of the solvent, and the resulting powder has an irregular shape or is contained inside the ceramic powder. Air gaps are likely to occur. Moreover, the coating 3 cannot be formed in a layer on the surface of the dielectric particles 1 as in the production method of the present invention.

また、上記本発明の製法に比較して、最高温度が、例えば、１０００℃よりも低温、特に、５００℃以下の温度で処理を行う従来の被膜の形成方法では、被膜成分７が溶解しないために誘電体粒子１の表面に形成されるセラミックスの被膜３は濡れ広がりが無く、このような被膜３には透過電子顕微鏡観察によれば格子模様が見られる。なお、本発明では被膜３に格子模様が見られる状態を結晶化しているとする。そのため、このような誘電体原料粉末を用いてスラリを調製する場合にボールミルを用いると、誘電体粒子１の表面に形成された被膜成分７が剥離したりする。そのため、被膜成分７が磁器中で偏析したり、誘電体粒子１自体の粒成長が生じたりする。
Further, in comparison with the production method of the present invention, the maximum temperature is, for example, lower than 1000 ° C., in particular, the conventional film forming method in which the treatment is performed at a temperature of 500 ° C. or less, because the film component 7 is not dissolved. the film 3 of the ceramic formed on the surface of the dielectric particles 1 without spreading, a lattice pattern is observed, according to transmission electron microscopy to such coating 3. In the present invention, it is assumed that a state in which a lattice pattern is seen in the coating 3 is crystallized. Therefore, when a slurry is prepared using such a dielectric raw material powder, if a ball mill is used, the coating component 7 formed on the surface of the dielectric particles 1 may be peeled off. Therefore, the coating component 7 is segregated in the porcelain, or the grain growth of the dielectric particles 1 itself occurs.

次に、本発明によって得られた誘電体原料粉末を用いて得られる誘電体磁器、ならびに、この誘電体磁器によって形成される積層セラミックコンデンサについて説明する。誘電体磁器は、上記誘電体原料粉末を成形し、焼成して得られる。そして、積層セラミックコンデンサは、誘電体層と電極層とが積層されており、この誘電体層が、本発明によって得られたチタン酸バリウム系粉末の焼結体である。この積層セラミックコンデンサは、例えば、以下のように製造することができる。
Next, a dielectric ceramic obtained by using the dielectric material powder obtained by the present invention and a multilayer ceramic capacitor formed by the dielectric ceramic will be described . Dielectrics porcelain, and molding the dielectric material powder, Ru obtained by firing. Then, the product layer ceramic capacitor, a dielectric layer and an electrode layer are laminated, the dielectric layer is a sintered body of barium titanate powder obtained by the present invention. This multilayer ceramic capacitor can be manufactured, for example, as follows.

まず、本発明によって得られたチタン酸バリウム系粉末を焼結助剤であるガラス成分とともに樹脂および必要に応じて溶媒と混合してスラリを調製する。焼結助剤としては、例えば、ＳｉＯ２−ＣａＯ−Ｂ２Ｏ３系ガラスが好適である。樹脂はポリビニルブチラール、ポリビニルアルコールなどを使用することができ、溶媒としては、例えば、水、アルコール、酢酸ブチル、酢酸エチルなどを使用することができる。
First, a barium titanate-based powder obtained by the present invention is mixed with a resin and optionally a solvent together with a glass component as a sintering aid to prepare a slurry. As the sintering aid, for example, SiO 2 —CaO—B 2 O 3 based glass is suitable. As the resin, polyvinyl butyral, polyvinyl alcohol, or the like can be used. As the solvent, for example, water, alcohol, butyl acetate, ethyl acetate, or the like can be used.

続いて、前記スラリをシート状に成形し誘電体グリーンシートを作製する。成形方法は特に限定するものではないが、例えば、ドクターブレード法などを採用することができる。次に、誘電体グリーンシートと電極パターンとを積層して積層体を得る。電極パターンとしては、例えば、銅、ニッケルまたはコバルトなどの卑金属粉末に、樹脂および溶媒を混合してなる導体ペーストを用いることができる。なお、誘電体グリーンシートおよび電極パターンの積層数は、特に限定するものではなく、所望の静電容量などに応じて適宜設定することができる。   Subsequently, the slurry is formed into a sheet shape to produce a dielectric green sheet. Although a shaping | molding method is not specifically limited, For example, a doctor blade method etc. are employable. Next, a dielectric green sheet and an electrode pattern are laminated to obtain a laminate. As the electrode pattern, for example, a conductive paste obtained by mixing a resin and a solvent with a base metal powder such as copper, nickel, or cobalt can be used. The number of laminated dielectric green sheets and electrode patterns is not particularly limited, and can be set as appropriate according to the desired capacitance.

次に、必要に応じて脱バインダ処理などを実施した後、この積層体を焼成し、さらに、焼成した積層体に外部電極などが適宜形成されて積層セラミックコンデンサが得られる。   Next, after removing the binder as necessary, this laminated body is fired, and further, external electrodes and the like are appropriately formed on the fired laminated body to obtain a multilayer ceramic capacitor.

焼成温度は、焼結助剤の種類および添加量、ならびに用いる誘電体原料粉末の粒子径に応じて適宜設定することができるが、例えば１１００〜１３００℃、好ましくは１１５０〜１２５０℃である。また、焼成雰囲気は、電極層の酸化を抑制するため、非酸化性雰囲気とすることが好ましい。 The firing temperature can be appropriately set according to the type and amount of the sintering aid and the particle diameter of the dielectric raw material powder used, and is, for example, 1100 to 1300 ° C, preferably 1150 to 1250 ° C. The firing atmosphere is preferably a non-oxidizing atmosphere in order to suppress oxidation of the electrode layer.

まず、誘電体粒子として表１に示す平均粒子径（Ｄ５０：粒度分布における５０％累積値における粒径）のチタン酸バリウム粒子（Ａ／Ｂ＝１．００５）を準備し、次いで被膜成分を準備した。被膜成分は表１に示す平均粒子径の各種元素の酸化物粉末を用いた。各種元素の添加量は酸化物換算でチタン酸バリウム１００モルに対して各０．１モルとした。   First, barium titanate particles (A / B = 1.005) having an average particle size (D50: particle size at 50% cumulative value in the particle size distribution) shown in Table 1 are prepared as dielectric particles, and then a coating component is prepared. did. As the coating component, oxide powders of various elements having average particle sizes shown in Table 1 were used. The amount of each element added was 0.1 mol per 100 mol of barium titanate in terms of oxide.

次に、誘電体粒子と被膜成分である各元素の酸化物粉末とを混合、乾燥して誘電体粒子の表面に被膜成分を付着させた複合粒子を調製した。被膜成分が酸化物粉末の場合、純度９９．６％のエチルアルコールを用いて、ボールミルを用いて混合し、次いで、大気中、温度１２０℃で２時間の乾燥を行い複合粒子を調製した。   Next, the composite particles were prepared by mixing the dielectric particles and the oxide powder of each element as the coating component, and drying them to adhere the coating component to the surface of the dielectric particles. When the coating component was an oxide powder, 99.6% purity ethyl alcohol was mixed using a ball mill, and then dried in air at a temperature of 120 ° C. for 2 hours to prepare composite particles.

被膜成分が溶液の場合は、表３に示す塩を用いた。この場合、純度９９．９５％のイオン交換水を用いて、各種元素の含まれる溶液と平均粒径が１００ｎｍのＢＴ粉末とを撹拌翼の付いた混合装置を用いて混合し、次いで、大気中、温度２００℃の温度でスプレードライの乾燥を行い複合粒子を調製した。原料溶液としてＹは硝酸イットリウム、Ｍｎは酢酸マンガン、Ｍｇは硝酸マグネシウムを用いた。各種元素の添加量は酸化物換算でチタン酸バリウム１００モルに対して各０．１モルとした。   When the coating component was a solution, the salts shown in Table 3 were used. In this case, using ion-exchanged water having a purity of 99.95%, a solution containing various elements and BT powder having an average particle size of 100 nm are mixed using a mixing device with a stirring blade, and then in the atmosphere. Then, spray drying was performed at a temperature of 200 ° C. to prepare composite particles. As raw material solutions, Y was yttrium nitrate, Mn was manganese acetate, and Mg was magnesium nitrate. The amount of each element added was 0.1 mol per 100 mol of barium titanate in terms of oxide.

次に、この複合粒子を図５に示した加熱炉を用いて、表１および表３の条件（温度、吸引力（層流）、温度勾配）にて熱処理を行い、誘電体原料粉末を調製した。温度は加熱炉の長さ方向中央部の炉内の温度とした。昇温速度は以下のように求めた。つまり、本発明の誘電体原料粉末の製法においては、吸引ポンプを用いて大気を排出することによって層流を調製しており、この場合、炉心管の直径は７５ｍｍ、長さは５ｍ、長さ方向の中央部が最高温度の領域であり、炉心管の上端は５０℃であった。複合粒子を通過させる周囲の温度変化は、気流が炉心管の上端の位置から中央部である２．５ｍの位置に達する時間から求めた。炉心管中央部付近の最高温度が１２５０℃であると、その温度差は１２００℃となり、吸引量１０Ｌ／ｍｉｎの場合の落下時間が５ｍあたり２秒であるので、加熱工程における複合粒子５の周囲の温度変化は１２００／１＝１２００℃／ｓｅｃとなる。この場合、炉心管の下端部側から空気を吸引する方法であるために、加熱工程および冷却工程における複合粒子５の周囲の温度変化は同じとした。なお、吸引しないで自然落下させた場合、高さ５ｍの炉心管の上端から回収部までの到達時間は１０秒であったが、この場合
、複合粒子が凝集し、焼結して直径が１０μｍ以上の大きさの凝集体となった（試料Ｎｏ．２０の平均粒子径は凝集体を構成する個々の粒子径の平均値である）。加熱の通過回数は、被膜成分として酸化物を用いたものは表１に記載したように３回または５回、被膜成分として硝酸イットリウム、硝酸マグネシウム、酢酸マンガンの溶液を用いた表３の場合は全て３回の通過回数とした。
Next, prepare the composite particles using a heating furnace as shown in FIG. 5, Table 1 and Table 3 conditions (temperature, suction force (laminar flow), temperature gradient) followed by heat treatment at, dielectric material powder did. The temperature was the temperature in the furnace at the center in the length direction of the heating furnace. The rate of temperature increase was determined as follows. That is, in the production method of the dielectric material powder of the present invention, are prepared laminar flow by exhausting air using a suction pump, in this case, the diameter of the core tube is 75 mm, length 5 m, the length The central part of the direction was the highest temperature region, and the upper end of the core tube was 50 ° C. Temperature changes in the ambient passing the composite particles was determined from the time the air flow reaches the location of 2.5m is a central part from the position of the upper end of the core tube. When the maximum temperature in the vicinity of the core tube center portion is at 1250 ° C., the temperature difference becomes the 1200 ° C., since dropping time in the case of suction amount 10L / min is 2 seconds per 5 m, the composite particles definitive enough to heat engineering 5 The ambient temperature change is 1200/1 = 1200 ° C./sec. In this case, since a method of sucking the air from the lower end of the core tube, the temperature change around the composite particles 5 in the heating and cooling steps were the same. Na us, if allowed to fall naturally without suction, the arrival time from the upper end of the core tube height 5m to the recovery unit was the 10 seconds, in this case, composite particles are agglomerated, in diameter and sintered Aggregates having a size of 10 μm or more were formed (the average particle size of sample No. 20 is the average value of the individual particle sizes constituting the aggregate). In the case of Table 3 using a solution of yttrium nitrate, magnesium nitrate and manganese acetate as the coating component , the number of heating passes is 3 or 5 times as described in Table 1 using an oxide as the coating component. All were set to 3 passes.

次に、得られた誘電体原料粉末について平均粒子径を求めた。また、同誘電体原料粉末について被膜の占有状態（誘電体粒子の表面に占める被膜の領域）および結晶状態ならびに厚みを透過電子顕微鏡を用いて評価し、表２および表４に記載した。被膜の厚みは得られた写真から上記の方法によって測定し、各粉末から誘電体粒子３個の写真を抽出して平均化して求めた。また、被膜の状態として、被膜の非晶質か否かの確認も、同様に３個の誘電体粒子の透過電子顕微鏡写真から、被膜に格子模様の見えないものを非晶質として評価した。なお、被膜の占有状態において全面と記載したのは、誘電体粒子の輪郭表面の９０％以上が非晶質もしくは結晶の被膜のいずれか一方で覆われている状態である。
Next, the average particle diameter was calculated | required about the obtained dielectric raw material powder. Further, the occupation state of the film (the area of the film occupying the surface of the dielectric particles), the crystal state and the thickness of the dielectric material powder were evaluated using a transmission electron microscope, and are shown in Tables 2 and 4 . The thickness of the coating was measured by the above method from the obtained photograph was obtained by averaging from the powder by extracting the dielectric particles three photographs. Further, as to the state of the coating, whether or not the coating was amorphous was similarly evaluated from the transmission electron micrographs of the three dielectric particles when the coating did not show a lattice pattern as amorphous. In addition, what is described as the entire surface in the occupied state of the coating is a state in which 90% or more of the contour surface of the dielectric particles is covered with either the amorphous or crystalline coating.

次に、得られた誘電体原料粉末を用いて成形体を作製し、ＴＭＡを用いて熱収縮曲線を求め、図３のようにして収縮開始温度を求めた。ＴＭＡの試料は１０ｍｍ×５ｍｍ×５ｍｍとした。ＴＭＡの温度は室温から１３００℃、雰囲気は大気中とした。   Next, a molded body was produced using the obtained dielectric raw material powder, a heat shrinkage curve was obtained using TMA, and a shrinkage start temperature was obtained as shown in FIG. The TMA sample was 10 mm × 5 mm × 5 mm. The temperature of TMA was from room temperature to 1300 ° C., and the atmosphere was in the air.

また、同誘電体原料粉末を用いて直径１２ｍｍ、厚み１ｍｍのペレット状の成形体を作製し、大気中にて２時間の焼成を行った。次に、得られた焼結体の各試料について結晶粒子の平均粒子径と粒子径のばらつき（ＣＶ：平均粒子径をｘ、標準偏差をσとしたときのσ／ｘ（％））を測定した。また、この焼結体試料の両主面にＩｎ−Ｇａの金属を塗布して、静電容量を測定し、試料の厚みと表面積から比誘電率を求めた。試料数は各１０個とした。結果を表２および表４に示す。
Further, the dielectric material powder diameter 12mm was used to prepare a pellet-shaped molded product having a thickness of 1 mm, it was fired for 2 hours at atmospheric aerial. Next, the variation of the average particle diameter and the particle size of the crystal grains terminal for each sample of the obtained sintered body (CV: average particle size x, when the standard deviation was σ σ / x (%)) to It was measured. In addition, In—Ga metal was applied to both main surfaces of the sintered body sample, the capacitance was measured, and the relative dielectric constant was determined from the thickness and surface area of the sample. The number of samples was 10 each. The results are shown in Table 2 and Table 4.

焼結体中における結晶粒子の平均粒子径と粒子径のばらつき（ＣＶ）は、得られた焼結体の破断面を研磨した後、走査型電子顕微鏡を用いて内部組織の写真を撮り、次いで、その写真に映し出されている結晶粒子の輪郭を画像処理し、各粒子を円と見立ててその直径を求め、その平均値を焼結体中の結晶粒子の平均粒子径とし、粒子径のばらつき（ＣＶ）を求めた。この場合、焼結体中の結晶粒子の断面は最大径のところの断面ではない場合が多いために原料粉末である誘電体粒子の平均粒子径よりも小さくなる場合がある。

Figure 0005025210
The average particle diameter and the variation in particle size of crystal grains in the sintered body (CV) is, after polishing the fracture surface of the obtained sintered body, take a picture of the internal structure with a scanning electron microscope, then , Image processing of the contours of the crystal particles shown in the photograph, each particle is regarded as a circle, the diameter is obtained, the average value is the average particle size of the crystal particles in the sintered body, and the particle size variation (CV) was determined. In this case, since the cross section of the crystal particles in the sintered body is often not the cross section at the maximum diameter, it may be smaller than the average particle diameter of the dielectric particles as the raw material powder.
Figure 0005025210

Figure 0005025210
Figure 0005025210

Figure 0005025210
Figure 0005025210

Figure 0005025210
Figure 0005025210

表１〜４の結果から明らかなように、本発明の製法により作製した試料は被膜が非晶質で誘電体粒子の表面に形成されていた。本発明により得られた誘電体原料粉末を用いて作製した焼結体は、誘電体粒子としてチタン酸バリウム粉末（ＢＴ粉末）を用いるとともに
、被膜成分としてＹ、ＭｇおよびＭｎの酸化物を用いた場合、または硝酸塩や酢酸塩などを溶液として用いて被膜を形成した場合のいずれにおいても、被膜を従来の液相法により形成した試料（Ｎｏ．３４）に比較して、焼結時の収縮開始温度が高まり、また、焼結体の粒成長も抑制され、粒子径のばらつきも小さかった。そして、本発明により得られた誘電体原料粉末を用いて作製した焼結体は被膜を従来の液相法により形成した試料（Ｎｏ．３４）に比較して比誘電率が高かった。
As is clear from the results in Tables 1 to 4, the sample produced by the production method of the present invention had an amorphous coating and was formed on the surface of the dielectric particles. The sintered body produced using the dielectric material powder obtained according to the present invention uses barium titanate powder (BT powder) as dielectric particles and oxides of Y, Mg and Mn as coating components. In either case, or in the case where a film is formed using nitrate or acetate as a solution, shrinkage starts during sintering as compared with the sample (No. 34) in which the film is formed by a conventional liquid phase method. The temperature increased, the grain growth of the sintered body was suppressed, and the variation in particle diameter was small. And the sintered compact produced using the dielectric raw material powder obtained by this invention had a high dielectric constant compared with the sample (No. 34) which formed the film by the conventional liquid phase method.

次に、実施例１における試料Ｎｏ．７の誘電体原料粉末を用いて積層セラミックコンデンサを作製した。焼結助剤としては、ＳｉＯ２＝５０、ＢａＯ＝２０、ＣａＯ＝２０、Ｌｉ２Ｏ＝１０（モル％）のガラスを用い、その添加量はチタン酸バリウム系粉末１００質量部に対して１．２質量部とした。予め、これらの原料粉末をジルコニアのボールミルを用いて溶媒としてイオン交換水を加えて１０時間混合した。
Next, sample no. A multilayer ceramic capacitor was prepared using 7 dielectric raw material powder. As the sintering aid, glass with SiO 2 = 50, BaO = 20, CaO = 20, Li 2 O = 10 (mol%) was used, and the amount added was 1 with respect to 100 parts by mass of the barium titanate powder. .2 parts by mass. In advance, ion-exchanged water was added to these raw material powders as a solvent using a zirconia ball mill and mixed for 10 hours.

次に、上記混合粉末１００質量部と、ブチラール７質量部と、酢酸ブチル１５質量部とを、ジルコニアボールを媒体として約６時間ボールミル混合しスラリーを調製した。次に、この誘電体スラリを用いて厚み２．５μｍの誘電体グリーンシートを作製し、この表面に、ニッケルペーストを用いて内部電極を形成し、内部電極付きグリーンシートを作製した。また、別途、上記の誘電体スラリを用いて、厚み５０μｍの保護用グリーンシートを作製した。次に、内部電極付きのグリーンシートを１００枚積層し、この積層体の上下面に保護層用グリーンシートを４枚づつ積層して熱圧着した後、個片に寸断して、２１型サイズの積層コンデンサグリーンチップを作製した。   Next, 100 parts by mass of the mixed powder, 7 parts by mass of butyral, and 15 parts by mass of butyl acetate were ball-milled for about 6 hours using zirconia balls as a medium to prepare a slurry. Next, a dielectric green sheet having a thickness of 2.5 μm was produced using the dielectric slurry, and an internal electrode was formed on the surface using nickel paste to produce a green sheet with an internal electrode. Separately, a protective green sheet having a thickness of 50 μm was prepared using the above-described dielectric slurry. Next, 100 green sheets with internal electrodes are laminated, and four protective layer green sheets are laminated on the upper and lower surfaces of the laminated body and thermocompression bonded. A multilayer capacitor green chip was produced.

次に、この積層コンデンサグリーンチップに対して、脱バインダ処理を実施した後、これを焼成した。脱バインダ処理は、大気中、毎時１５℃の割合で４００℃まで昇温し、４００℃で５時間保持した後、炉内放冷するというプロファイルで実施した。   Next, the multilayer capacitor green chip was subjected to binder removal processing and then fired. The binder removal treatment was carried out with a profile in which the temperature was raised to 400 ° C. at a rate of 15 ° C. per hour in the atmosphere, held at 400 ° C. for 5 hours, and then allowed to cool in the furnace.

また、焼成は、窒素と水素との混合ガス雰囲気中で、毎時２００℃の割合で常温から９００℃まで昇温し、９００℃で１時間保持しながらマスフローコントローラを動作させてニッケルの酸化還元平衡酸素分圧よりも２桁下になるように炉内の酸素分圧を調整し、その後、各温度でこの酸素分圧が保持されるようにマスフローコントローラを動作させながら、１１７０℃の温度まで毎時２００℃で昇温し、更にその温度で２時間保持した後、毎時２００℃の割合で常温まで降温するというプロファイルで行った。   Firing is performed in a mixed gas atmosphere of nitrogen and hydrogen at a rate of 200 ° C. per hour from normal temperature to 900 ° C., and maintained at 900 ° C. for 1 hour to operate the mass flow controller and perform nickel redox equilibrium. Adjust the oxygen partial pressure in the furnace so that it is two orders of magnitude lower than the oxygen partial pressure, and then operate the mass flow controller to maintain this oxygen partial pressure at each temperature until the temperature reaches 1170 ° C. every hour. The temperature was raised at 200 ° C., held at that temperature for 2 hours, and then lowered to room temperature at a rate of 200 ° C. per hour.

その後、焼成したチップをバレル研磨して面取りを施し、銅ペーストを内部電極が露出した部分に塗布して焼付けを行って端子電極を形成し、この端子電極にニッケルめっきおよびハンダめっきを順次施して、積層セラミックコンデンサを製造した。得られた積層セラミックコンデンサの寸法は２ｍｍ×１．２ｍｍ×０．６ｍｍであった。   After that, the fired chip is barrel polished to chamfer, and a copper paste is applied to the exposed portion of the internal electrode and baked to form a terminal electrode, which is then subjected to nickel plating and solder plating in sequence. A multilayer ceramic capacitor was manufactured. The dimensions of the obtained multilayer ceramic capacitor were 2 mm × 1.2 mm × 0.6 mm.

比較例として、チタン酸バリウム粒子の表面にＹ、Ｍｇ、Ｍｎ成分を液相法で付着させたチタン酸バリウム系粉末である、実施例１の試料Ｎｏ．３４の誘電体原料粉末を用いて上記と同様の製法により積層セラミックコンデンサを作製した。   As a comparative example, the sample No. 1 of Example 1, which is a barium titanate powder in which Y, Mg, and Mn components are adhered to the surface of barium titanate particles by a liquid phase method. A monolithic ceramic capacitor was produced by the same production method as described above using 34 dielectric material powders.

得られた積層セラミックコンデンサについて静電容量と高温負荷寿命を評価した。   The obtained multilayer ceramic capacitor was evaluated for capacitance and high-temperature load life.

積層セラミックコンデンサの静電容量はＬＣＲメータを用いて、２５℃において、ＡＣ電圧１Ｖ、周波数１ｋＨｚの条件にて３０秒後の値として評価した。高温負荷寿命は１２５℃、１２．６Ｖで評価し、時間経過における不良の発生頻度を調べ、不良数５０％での時間（ＭＴＴＦ）を求めた。試料数は１００個とした。 The capacitance of the multilayer ceramic capacitor was evaluated as a value after 30 seconds at 25 ° C. under the conditions of an AC voltage of 1 V and a frequency of 1 kHz using an LCR meter. The high-temperature load life was evaluated at 125 ° C. and 12.6 V, the frequency of occurrence of defects over time was examined, and the time when the number of defects was 50% (MTTF) was determined. The number of samples was 100.

その結果、本発明の製法で得られたチタン酸バリウム系粉末を用いて作製した試料は静電容量が平均で４．６μＦであったのに対し、比較例の試料の静電容量は平均で３．９μＦであった。   As a result, the sample produced using the barium titanate-based powder obtained by the production method of the present invention had an average capacitance of 4.6 μF, whereas the sample of the comparative example had an average capacitance. It was 3.9 μF.

また、高温負荷寿命であるＭＴＴＦは本発明の製法で得られたチタン酸バリウム系粉末を用いて作製した試料は１２５時間であったのに対し、比較例の試料は９０時間であった。   In addition, the MTTF, which is a high temperature load life, was 125 hours for the sample prepared using the barium titanate-based powder obtained by the production method of the present invention, whereas the sample for the comparative example was 90 hours.

誘電体原料粉末の断面の透過電子顕微鏡写真である。It is a transmission electron micrograph of a cross section of Yuden material powder. 図１の透過電子顕微鏡写真の誘電体原料粉末の模式図である。It is a schematic diagram of the dielectric material powder of the transmission electron micrograph of FIG. 誘電体原料粉末の成形体を熱機械分析（ＴＭＡ）を用いて得られた熱収縮曲線である。熱収縮曲線Ａは本発明の誘電体原料粉末、熱収縮曲線Ｂは液相法によって誘電体粒子表面に被膜成分を単に付着させただけの誘電体原料粉末である。It is the heat contraction curve obtained by using the thermomechanical analysis (TMA) for the compact of the dielectric material powder. The heat shrinkage curve A is the dielectric raw material powder of the present invention, and the heat shrinkage curve B is the dielectric raw material powder in which the coating component is simply adhered to the surface of the dielectric particles by the liquid phase method. 本発明の誘電体原料粉末の製法に用いる複合粒子の模式図である。It is a schematic diagram of the composite particle used for the manufacturing method of the dielectric material powder of this invention. 本発明の誘電体原料粉末の製法に用いる加熱炉の断面模式図である。It is a cross-sectional schematic diagram of the heating furnace used for the manufacturing method of the dielectric material powder of this invention.

符号の説明Explanation of symbols

１ 誘電体粒子
３ 被膜
１１ 炉本体
１３ 原料投入フィーダ
１５ 粉末回収部
１７ 炉心管
１９ 加熱部
２３ 空間

DESCRIPTION OF SYMBOLS 1 Dielectric particle 3 Coating 11 Furnace main body 13 Raw material input feeder 15 Powder collection | recovery part 17 Furnace core tube 19 Heating part 23 Space

Claims (3)

ペロブスカイト型結晶構造を有する誘電体粒子を、希土類元素と、Ｍｇ、Ｍｎ、Ｗ、Ｍｏ、ＶおよびＣｒのうち少なくとも１種の元素とを含む被膜成分とともに溶媒中で混合し、乾燥させて、前記誘電体粒子の表面に該誘電体粒子よりもサイズの小さい前記被膜成分が付着した複合粒子を調製する工程と、該複合粒子を構成している前記被膜成分を５００℃／ｓｅｃ以上の温度変化で加熱溶融させる加熱工程と、溶融した前記被膜成分を５００℃／ｓｅｃ以上の温度変化で冷却固化させることにより、前記誘電体粒子の断面の輪郭の９０％以上の領域に非晶質の被膜を形成する冷却工程とを有することを特徴とする誘電体原料粉末の製法。 Dielectric particles having a perovskite crystal structure are mixed in a solvent together with a coating component containing a rare earth element and at least one element of Mg, Mn, W, Mo, V and Cr, and dried, A step of preparing composite particles in which the coating component having a size smaller than that of the dielectric particles is attached to the surface of the dielectric particles; and the coating component constituting the composite particles is changed by a temperature change of 500 ° C./sec or more. An amorphous coating is formed in a region of 90% or more of the cross-sectional contour of the dielectric particles by heating and melting and solidifying the melted coating component by cooling at a temperature change of 500 ° C./sec or more. A method of producing a dielectric material powder, comprising: a cooling step. 前記加熱工程および前記冷却工程において、最高温度が１０００℃以上に設定された領域を有する炉心管内に、前記複合粒子を通過させることにより、前記複合粒子を１０００℃／ｓｅｃ以上の温度変化で加熱し、ひきつづき１０００℃／ｓｅｃ以上の温度変化で冷却することを特徴とする請求項１に記載の誘電体原料粉末の製法。   In the heating step and the cooling step, the composite particles are heated at a temperature change of 1000 ° C./sec or more by passing the composite particles through a core tube having a region where the maximum temperature is set to 1000 ° C. or more. The method for producing a dielectric raw material powder according to claim 1, wherein the dielectric raw material powder is cooled at a temperature change of 1000 ° C./sec or more. 前記被膜成分として、平均粒子径が１０〜２０ｎｍの粒子を用いることを特徴とする請求項１または２に記載の誘電体原料粉末の製法。   The method for producing a dielectric material powder according to claim 1 or 2, wherein particles having an average particle size of 10 to 20 nm are used as the coating component.
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