JP5307379B2 - Plate-like polycrystalline particles, method for producing plate-like polycrystalline particles, method for producing crystal-oriented ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plate-like polycrystalline particle in which a particle size and an aspect ratio are easily adjusted. <P>SOLUTION: A plate-like polycrystalline particle 10 is produced by forming inorganic particles into a self-supported, sheet-like shaped body with a predetermined thickness (15 &mu;m) or less, firing the shaped body, and crushing and classifying the fired shaped body by passing through a mesh having openings with a predetermined size. The inorganic particles are composed of an oxide having a perovskite structure and growing into crystal grains with an isotropic and polyhedral shape (e.g., cubic shape). Since grain growth in the thickness direction is limited and grain growth is more promoted in the surface direction of the sheet, it is possible to obtain crystal grains 12 having a high aspect ratio and a high degree of orientation. Therefore, in the plate-like polycrystalline particle 10, in most parts, the number of crystal grains 12 present in the thickness direction of the particle at any one point is one, and a high aspect ratio and a high degree of orientation are achieved. In the plate-like polycrystalline particle 10, crystal grains 12 are bonded together at grain boundaries 14, and crushing easily takes place at the grain boundaries 14. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to plate-like polycrystalline particles, a method for producing plate-like polycrystalline particles, and a method for producing crystal-oriented ceramics.

2. Description of the Related Art Conventionally, as crystal-oriented ceramics, those that improve piezoelectric characteristics by increasing the degree of orientation of a specific crystal plane included in a crystal have been proposed (see Patent Documents 1 and 2). In addition, as a method for producing crystal-oriented ceramics, for example, a host material A having shape anisotropy and a guest material B having crystal matching with at least one crystal plane of the host material A and having a small crystal anisotropy Including a mixing step of mixing, an orientation step of orienting the crystal plane of the host material A, and a firing step of orienting the crystal plane of the guest material B by heating the oriented one. Proposals have been made to obtain ceramics with improved orientation even when the guest material B is used (see, for example, Patent Documents 2 and 3). Furthermore, the thing etc. which improve the orientation of host material itself by hydrothermal synthesis are proposed (patent document 4).
Japanese Patent Laid-Open No. 11-60333 JP 2003-12373 A Japanese Patent Laid-Open No. 10-330184 JP 2007-22857 A

  However, in the manufacturing methods described in Patent Documents 1 to 3, since the host material is a single crystal, the particle size, aspect ratio, and the like of the host material cannot be easily changed. In addition, in the production of this crystal-oriented ceramic, if the aspect ratio of the host material is increased in order to favor the orientation during molding, the primary particle size also increases. When this is used, for example, the sinterability decreases. Or the density of the crystallographically oriented ceramics may be reduced, or the particle size may be increased, resulting in problems such as a decrease in mechanical strength and insulation. Further, in Patent Document 2, after obtaining a plate crystal in a composition having a layered perovskite structure, a part of this composition is substituted to synthesize a host material composed of a desired element. May not proceed sufficiently, and undesirable elements may remain in the final material. Moreover, the process was complicated. Furthermore, since the host material described in Patent Document 4 is produced by hydrothermal synthesis in which an aqueous solution containing a raw material is synthesized at a high temperature and high pressure, the synthesis process takes time.

  The present invention has been made in view of such problems, and is capable of easily adjusting the particle size and aspect ratio. Plate-like polycrystalline particles, plate-like polycrystalline particle production method, and crystal-oriented ceramic production method Is one of the purposes. Another object is to provide plate-like polycrystalline particles having a more uniform composition, a method for producing plate-like polycrystalline particles, and a method for producing crystal-oriented ceramics. Another object of the present invention is to provide plate-like polycrystalline particles, a method for producing plate-like polycrystalline particles, and a method for producing crystal-oriented ceramics that can increase the degree of crystal orientation by simpler treatment.

  In order to achieve at least a part of the object described above, the present inventors formed inorganic particles into a self-supporting sheet-like molded body having a thickness of 15 μm or less, and this molded body was substantially combined with the molded body. Adjacent to an inert layer that does not react or is fired as it is, and the fired compact is crushed and classified by passing through an opening of a predetermined size. The present inventors have found that the grain size and aspect ratio of the crystal grains can be easily adjusted, and that the degree of orientation of the crystal grains can be increased by simpler processing, and the present invention has been completed.

That is, the plate-like polycrystalline particles of the present invention are
Including a plurality of crystal grains,
There is substantially one crystal grain in the thickness direction, and the plurality of crystal grains are bonded at a grain boundary portion with a specific crystal plane aligned.

The method for producing the plate-like polycrystalline particles of the present invention includes
A method for producing plate-like polycrystalline particles containing a plurality of crystal particles,
A molding step of molding the inorganic particles into a self-supporting sheet-like molded body having a thickness of 15 μm or less;
A firing step in which the molded body is adjacent to an inert layer that does not substantially react with the molded body, or is fired as the molded body;
A pulverizing step of pulverizing and classifying the fired compact by passing through an opening of a predetermined size;
Is included.

Furthermore, the method for producing the crystallographically-oriented ceramic of the present invention includes:
A mixing step of mixing the plate-like polycrystalline particles of the present invention described above and the raw material powder;
A second forming step of orienting the plate-like polycrystalline particles in a predetermined direction in the mixed powder to form a predetermined secondary compact;
A second firing step of firing the secondary molded body so as to orient the raw material powder in a direction in which the plate-like polycrystalline particles are oriented;
Is included.

  According to the plate-like polycrystalline particles of the present invention, the method for producing plate-like polycrystalline particles and the method for producing crystal-oriented ceramics, the inorganic particles are formed into a self-supporting sheet-like molded body having a predetermined thickness, and this is fired. Since the fired compact may be crushed and classified by passing through an opening having a predetermined size, the degree of crystal orientation can be increased by a simpler treatment. Further, the plate-like polycrystalline particles have a structure in which the crystal grains are bonded at the grain boundary part, and the number of the crystal grains in the thickness direction is substantially one, and it is easy to crush at the grain boundary part. The particle size, aspect ratio, etc. can be easily adjusted. Further, since it is not necessary to add an additive or the like or go through a composition containing an undesired element, a more homogeneous composition can be obtained. Note that “no need to add an additive or the like” does not exclude the addition of an additive to the present invention to further increase the degree of orientation.

  The plate-like polycrystalline particles of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram illustrating an example of the plate-like polycrystalline particle 10 of the present embodiment. The plate-like polycrystalline particle 10 includes a plurality of crystal particles 12 having a specific crystal face 11, and is substantially one crystal grain in the thickness direction. 11 are aligned at the grain boundary portion 14 in a state in which 11 are aligned. That is, the plate-like polycrystalline particle 10 has a shape in which a plurality of crystal particles 12 having a specific crystal plane 11 are arranged in a two-dimensional manner. The “state in which the specific crystal planes 11 are aligned” means that the crystal planes 11 of the plurality of crystal grains 12 are on the same plane (FIG. 1A) or the crystal plane 11 is not on the same plane. When the facing directions are the same (FIG. 1 (b)), the crystal planes 11 of the plurality of crystal grains 12 are approximately on the same plane or the same plane even if the crystal plane 11 is directed in a different direction. Although not above, the state where the crystal plane 11 is facing is the same (FIG. 1C). The plate-like polycrystalline particles 10 are obtained by forming inorganic particles into a sheet-like formed body, and pulverizing the fired formed body obtained by firing the formed body and growing the grains. Here, for convenience of explanation, an unfired sheet-shaped molded body is referred to as a “molded body”, a sheet-shaped molded body after firing is referred to as a “fired molded body”, and the fired molded body is defined as a predetermined body. Those that have been crushed and classified into particle sizes are referred to as “plate-like polycrystalline particles”.

  The plate-like polycrystalline particles 10 have substantially one crystal particle in the thickness direction. The term “substantially one crystal grain in the thickness direction” means that even if there is a part where the crystal grains 12 overlap in some parts, the crystal grains 12 do not overlap in most other parts. It means that only one crystal particle 12 is included. Further, most of the plate-like polycrystalline particles 10 such as the central portion are in a state in which two or more crystal particles 12 are combined, and only one end portion is not included in the thickness direction. Since the plate-like polycrystalline particles 10 are limited in the materials present in the thickness direction, when grains are grown by firing or the like, the plate-like polycrystalline particles 10 have a single crystal particle 12 in the thickness direction, and are more planar than the thickness direction. Grain growth is promoted in the direction. For this reason, the flat crystal particles 12 are arranged in the plane direction, and the specific crystal plane 11 is oriented. The plate-like polycrystalline particles 10 may have grain growth of the crystal grains 12 that does not reach the thickness of the sheet-like molded body or grains with different orientations of the crystal plane 11 during grain growth. As shown in FIGS. 1B and 1C, there are locally overlapping portions of the crystal grains 12 and those having different directions in which the crystal plane 11 faces. The crystal grains 12 are joined at the grain boundary part 14. In this plate-like polycrystalline particle 10, the portion containing only one crystal particle 12 is preferably 70% or more, more preferably 80% or more in terms of the area ratio of the plate-like polycrystalline particle 10, and 90% % Or more is most preferable. This area ratio is obtained as the ratio of the area included in the obtained SEM photograph by performing electron microscope observation (SEM observation) with the plate-like polycrystalline particles 10 dispersed as much as possible. The area of the portion including only one crystal grain 12 in the thickness direction can be predicted from the total area of crystal grains whose length in the plane direction is equal to or greater than the thickness. In this plate-like polycrystalline particle 10, the portion where the crystal particles 12 overlap is a part of the whole (for example, the area ratio is 30% or less), and it is relatively easy at the grain boundary portion 14 where the crystal particles 12 are bonded to each other. Can be crushed.

  In the plate-like polycrystalline particle 10 of the present invention, the length Y in the longitudinal direction of the plate-like polycrystalline particle 10 (see FIG. 1A) can be 1.0 mm or less, 50 μm or less, and 20 μm or less. . This length Y can be appropriately changed according to the size of the target plate-like polycrystalline particle 10. Further, the aspect ratio (Y / W) of the plate-like polycrystalline particle 10 that is the ratio of the length Y in the longitudinal direction of the plate-like polycrystalline particle 10 to the thickness W of the plate-like polycrystalline particle 10 is 2 or more and 100 or less. It is preferable that For example, when the plate-like polycrystalline particles 10 are used as a raw material for crystal orientation of crystal-oriented ceramics, if the aspect ratio of the plate-like polycrystalline particles 10 is 2 or more, the orientation during molding is facilitated, and the crystal orientation is improved. If it is 100 or less, for example, in the crystal-oriented ceramic mixing step described later, it is difficult to be pulverized and the aspect ratio can be maintained, so that a molded body in which the plate-like polycrystalline particles 10 are oriented can be easily obtained. be able to. Here, the thickness W of the plate-like polycrystalline particles 10 is the length of the thickest portion of the thickness of the plate-like polycrystalline particles 10. The plate-like polycrystalline particles 10 are preferably formed with a thickness W of 15 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less, and most preferably 2 μm or less. The thickness W is preferably formed to be 0.1 μm or more. If the thickness W is 0.1 μm or more, the flat plate-like polycrystalline particles 10 can be easily formed, and if the thickness W is 15 μm or less, the degree of orientation can be further increased. In addition, the thickness W of the plate-like polycrystalline particles 10 is usually substantially the same length as the thickness Z of the crystal particles 12. The aspect ratio of the plate-like polycrystalline particles 10 is determined as follows. First, SEM observation is performed using a scanning electron microscope, and the thickness W of the plate-like polycrystalline particles 10 is obtained from the photographed SEM photograph or the like. Next, the plate-like polycrystalline particles 10 are put in a solvent such as alcohol so as to be 1 to 10% by weight, and dispersed using, for example, ultrasonic waves for 30 minutes, and this dispersion is spun at 1000 to 4000 rpm. By coating and coating the glass substrate, the plate-like polycrystalline particles 10 are made into a thin layer so that they do not overlap as much as possible and the crystal face 11 included in the plate-like polycrystalline particles 10 is parallel to the substrate surface. SEM observation is performed in this state, and the crystal plane of the plate-like polycrystalline particles 10 is observed in a field of view containing about 5 to 30 plate-like polycrystalline particles 10, and the plate-like polycrystalline is obtained from the photographed SEM photograph. The longest length Y of the particle 10 is obtained. At this time, the overlapping plate-like polycrystalline particles 10 may be ignored. Next, the obtained longest length Y is assumed to be the particle size of the plate-like polycrystalline particle 10, and this particle size is divided by the thickness W of the plate-like polycrystalline particle 10 to obtain the aspect ratio of each plate-like polycrystalline particle 10. Is calculated, and the average of these values is taken as the aspect ratio of the plate-like polycrystalline particles 10.

In the plate-like polycrystalline particle 10 of the present invention, the degree of orientation of the specific crystal plane 11 is preferably 25% or more, more preferably 30% or more, and 60% or more by the Lotgering method. Is most preferred. If the degree of orientation is 25% or more, for example, it can be said that the degree of orientation is sufficient to obtain a crystal-oriented ceramic by forming the plate-like polycrystalline particles 10 by further secondary orientation. When this degree of orientation is 60% or more, higher characteristics can be obtained. The specific crystal plane 11 may be a pseudo cubic (100) plane in the plane of the fired molded body. This pseudo-cubic (100) is an isotropic perovskite type oxide, which has a slightly distorted structure such as tetragonal, orthorhombic and trigonal crystals, but the distortion is slight. It means to display with Miller index. Here, the degree of orientation by the Lotgering method is determined by XRD diffraction by placing the plate-like polycrystalline particle 10 on a substrate as a sample holder with the crystal plane 11 included in the plate-like polycrystalline particle 10 as uniform as possible. The pattern was measured and determined by the following formula (1). The measurement of the XRD diffraction pattern is performed by performing the same process as the sample adjustment for SEM observation when obtaining the aspect ratio described above, so that the crystal planes 11 included in the plate-like polycrystalline particles 10 are not overlapped as much as possible. The plate-like polycrystalline particles 10 are dispersed in a thin layer so that is parallel to the substrate surface such as glass, and measurement is performed in this state. In addition, it is preferable to confirm by SEM observation etc. whether most of the plate-like polycrystalline particles 10 are dispersed. In this formula (1), ΣI (hkl) is the sum of X-ray diffraction intensities of all crystal planes (hkl) measured on the plate-like polycrystalline particles, and ΣI0 (hkl) is the same as that of the plate-like polycrystalline particles. This is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for the non-oriented composition, and Σ'I (HKL) is the crystallographically equivalent measured by the plate-like polycrystalline particles This is the sum of the X-ray diffraction intensities of a specific crystal plane (for example, (100) plane), and the specific crystal plane measured for Σ'I0 (HKL) having the same composition as that of the plate-like polycrystalline particles and having no orientation. Is the sum of the X-ray diffraction intensities.

  In the plate-like polycrystalline particle 10 of the present invention, the crystal particle 12 is preferably formed with a thickness Z of 15 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less, and most preferably 2 μm or less. preferable. The thickness Z is preferably formed to be 0.1 μm or more. If the thickness Z is 0.1 μm or more, the flat plate-like polycrystalline particles 10 can be easily formed, and if the thickness Z is 15 μm or less, the degree of orientation can be further increased. If the thickness Z is 15 μm or less, even if inorganic particles that grow into isotropic and polyhedral crystal grains are included, grain growth in the thickness direction is limited. Since the grain growth of the crystal grains 12 is further promoted in the plane direction, a specific crystal plane grows in the plane of the plate-like polycrystalline grains 10, thereby increasing the aspect ratio and the degree of orientation.

  In the plate-like polycrystalline particle 10 of the present invention, the aspect ratio of the crystal particle 12 which is the ratio of the length X (see FIG. 1A) in the direction of the crystal plane 11 of the crystal particle 12 to the thickness Z of the crystal particle 12 (X / Z) is preferably 1 or more, more preferably 2 or more, and still more preferably 4 or more. When the aspect ratio is 2 or more, since the crystal grains 12 are easily oriented, the degree of orientation of the plate-like polycrystalline grains is also increased. This aspect ratio is preferably 50 or less. When the aspect ratio is 50 or less, it is easy to adjust the size of the plate-like polycrystalline particles 10. The aspect ratio of the crystal grains 12 is obtained as follows. First, SEM observation is performed using a scanning electron microscope, and the thickness Z of the crystal particle 12 is obtained from the photographed SEM photograph or the like. Next, similarly to the aspect ratio of the plate-like polycrystalline particles 10 described above, SEM observation is performed in a state where the plate-like polycrystalline particles 10 are dispersed in a thin layer so that they do not overlap as much as possible. In the field of view included in about one, the crystal plane of the plate-like polycrystalline particle 10 is observed, and the longest length X of the crystal plane 11 of the crystal grain 12 is obtained from the photographed SEM photograph. At this time, the overlapping plate-like polycrystalline particles 10 may be ignored. Next, the longest length X of the obtained crystal plane 11 is assumed to be the grain size of the crystal grain 12, and the grain ratio is divided by the thickness Z of the crystal grain 12 to calculate the aspect ratio of each crystal grain 12. Is an aspect ratio of the crystal grains 12 included in the plate-like polycrystalline particles 10.

  In the plate-like polycrystalline particle 10 of the present invention, the length X in the direction of the crystal plane 11 of the crystal particle 12 is preferably 50 μm or less, more preferably 25 μm or less, and most preferably 20 μm or less. preferable. If the length X is 50 μm or less, it is easy to adjust the size of the plate-like polycrystalline particles 10.

  Y / X, which is the ratio of the length X in the crystal plane direction of the crystal particles 12 and the length Y in the longitudinal direction of the plate-like polycrystalline particles 10, is preferably 3 or more and 100 or less. For example, when the plate-like polycrystalline particles 10 are used as a raw material for crystal orientation of crystal-oriented ceramics, when Y / X is 3 or more, the aspect ratio of the plate-like polycrystalline particles 10 can be increased. If it is 100 or less, for example, since the grain index of the plate-like polycrystalline particles 10 contained in the crystal-oriented ceramic is reduced, it is easy to orient and form the crystal-oriented ceramic.

  In the plate-like polycrystalline particles 10 of the present invention, the crystal particles 12 may be composed of inorganic particles that grow into isotropic and polyhedral crystal particles, or inorganic particles that grow into anisotropic crystal particles. It may be constituted by. Here, growing to isotropic and polyhedral crystal grains is considered to allow a specific crystal plane to be grown depending on the situation. Here, even if inorganic particles that grow into isotropic and polyhedral crystal grains are included, grain growth in the thickness direction is limited, and grain growth is further promoted in the plane direction. Crystal grains having a preferred direction in the in-plane direction have a large aspect ratio and a high degree of orientation by selectively growing in the plane direction by taking in crystal grains that do not have the preferred direction of crystal growth in the plane. It becomes. Among the polyhedral shapes, those that grow into a hexahedral shape are preferable. In the case of a hexahedron, when a flat plate shape is used, particles having a surface parallel to two large planes (also referred to as sheet surfaces) of the flat plate shape are grown on the other four planes except the two planes. Is included in all orientations in the molded body, and therefore, when isotropic grain growth occurs in the molded body, the two sheet surfaces expand without difficulty, which is preferable because particles having a large aspect ratio can be easily obtained. The crystal particles 12 are preferably composed of an oxide having a perovskite structure. Some oxides having a perovskite structure grow in the form of pseudocubic dice, and the (100) plane (or (001) plane) grows in the surface of the molded body, so that the crystal plane is perpendicular to the sheet plane. (100) (or (001) plane) is preferred because it is easily oriented. The crystal particles 12 included in the plate-like polycrystalline particles 10 may be anisotropic or isotropic, but are preferably anisotropic.

In the plate-like polycrystalline particle 10 of the present invention, the crystal particle 12 is mainly composed of an oxide represented by the general formula ABO ₃ , and the A site is one or more selected from Li, Na, K, Bi and Ag. In addition, the B site may be a particle containing one or more selected from Nb, Ta and Ti, and among these, (Li _X Na _Y K _Z ) Nb _M Ta _N O ₃ and (Bi _X Na _Y K _Z Ag _N ) TiO _{3 and the} like (X, Y, Z, M, and N represent any number) are particularly preferable. By doing so, it is easy to obtain crystal grains having a large aspect ratio and a specific crystal plane grown at a predetermined thickness (for example, 15 μm or less). Note that elements other than those listed here may be included. At this time, it is preferable that A / B of the crystal particles 12 before firing (referring to a firing step described later) is 1.0 or more and 1.1 or less. When the A / B of the oxide represented by the general formula ABO ₃ is 1.0 or more and 1.1 or less, the aspect ratio and the degree of orientation can be increased. Here, although an example of an oxide represented by the chemical formula ABO ₃ was shown, the present invention is not limited to this example, but includes, for example, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , MgO, CaO, Y ₂ O ₃ , SnO. ₂ , oxides such as ZnO and SiO ₂ and composite oxides such as PZT, BaTiO ₃ , BiFeO ₃ and YBa ₂ Cu ₃ O ₇ , nitrides such as AlN, Si ₃ N ₄ and BN, CaB ₆ , MgB ₂ , Borides such as LaB ₆ , carbides such as TiC, SiC, and WC, and tellurium compounds such as Bi ₂ Te ₃ , Bi ₂ Sb ₈ Te ₁₅ , and PbTe, CrSi ₂ , MnSi _1.73 , FeSi ₂ , CoSi ₂ It can also be applied to silicide-based materials such as metals, alloys, and intermetallic compounds. Alternatively, the crystal particle contains an oxide represented by the general formula ABO ₃ as a main component, the A site contains Pb, and the B site contains one or more selected from Mg, Zn, Nb, Ni, Ti, and Zr. It may be a particle.

  Next, the manufacturing method of the plate-like polycrystalline particle 10 will be described. The method for producing plate-like polycrystalline particles of the present invention includes (1) a preparation step of inorganic particles that are raw materials for plate-like polycrystalline particles, (2) a forming step from inorganic particles to a sheet-like formed body, (3) A step of firing the molded body, and (4) a step of pulverizing the mesh of the fired fired body will be described in the order of these steps.

(1) Inorganic particle preparation step The inorganic material used for the plate-like polycrystalline particles 10 grows into anisotropically shaped crystal particles under a predetermined firing condition, that is, a crystal whose growth shape under the predetermined firing condition is anisotropic. What grows into particles, grows into isotropic and polyhedral crystal grains under a predetermined firing condition, that is, grows under isotropic and polyhedral crystal grains under a predetermined firing condition. it can. In this regard, in the present invention, since a sheet-like molded body having a thickness of 15 μm or less is fired and grain growth is performed, grain growth in the thickness direction of the molded body is limited, and in the surface direction of the molded body, Since the grain growth is further promoted, it is possible to produce the plate-like polycrystalline particles 10 by using those which grow into isotropic and polyhedral crystal grains under predetermined firing conditions, for example, those which grow into cubes. It can be done. Here, the “growth form in a predetermined firing condition” is defined as a morphology that is observed when crystals of an inorganic material reach an equilibrium under a given heat treatment condition. For example, a bulk is fired to promote crystallization. In this case, it is obtained by observing the shape of the surface particles. Further, the “anisotropic shape” means, for example, a plate shape, a strip shape, a column shape, a needle shape, a scale shape, or the like having a large ratio (aspect ratio) between the major axis length and the minor axis length (for example, an aspect ratio of 2 or more) ). Further, “isotropic and polyhedral shape” refers to a cubic shape, for example. Here, in general, the morphology of crystal grains produced by grain growth is almost spherical when the grain growth temperature is sufficiently low, such as 400 ° C. or less, with respect to the melting point or decomposition temperature of the solid. Originally, although the atomic arrangement is anisotropic and there is a difference in the growth rate depending on the crystal plane, the spherical grains grow because the solid atoms are very difficult to move. On the other hand, when the melting point or decomposition temperature of the solid is close to the temperature at which the grain grows, for example, when the temperature difference between them is within 200 ° C., the movement of the atoms on the grain surface during grain growth becomes active, resulting in the crystal structure. Surface morphology appears. That is, in the grain growth, a difference in the growth rate due to the crystal plane comes out, and the slow growth crystal plane develops, but the fast growth crystal plane becomes smaller or disappears. The morphology determined by the difference in the plane growth rate is called a growth type. As described above, the growth shape is anisotropic or multi-faceted, and as described above, in addition to materials with a solid melting point or decomposition temperature close to the temperature at which grains grow, low melting point compounds such as glass are fluxed. A system is preferably selected which is added to cause grain growth via a flux. This is because the movement of solid constituent elements on the particle surface becomes active through the flux. In addition, among inorganic materials that grow into a polyhedral shape, those that grow into a hexahedral shape can be used. If it is a hexahedron, when it is made into a flat plate shape, the particles having a surface parallel to the flat plate-like sheet surface are included in all orientations in the molded body as growth surfaces other than the two surfaces. Therefore, when the grains grow isotropically in the molded body, the two sheet surfaces expand without difficulty, which is preferable because it is easy to obtain particles having a large aspect ratio. For the same reason, a column shape such as a hexagonal column or an octagonal column can be used. An additive for promoting grain growth may be added for the purpose of obtaining crystal grains having a large aspect ratio. This inorganic material is preferably an oxide having a perovskite structure. Further, the fired crystal is an oxide represented by the general formula ABO ₃ , and this A site is Li, Na, K, Bi and Ag. It is preferable to use one that includes one or more selected from the group B and the B site includes one or more selected from Nb, Ta, and Ti. For example, as an inorganic material, a part of the NaNbO ₃ A site is substituted with Li, K, etc., and a part of the B site is substituted with Ta ((Li _X Na _Y K _Z ) Nb _M Ta _N O ₃ : X, Y, Z, M, and N represent an arbitrary number), since the growth shape at 900 ° C. to 1300 ° C. becomes a cubic shape. Note that elements other than those listed here may be added. In the case of using (Bi _0.5 Na _0.5-x K _x ) TiO ₃ as the main composition, X> 0.01 is preferable because the growth shape becomes a cubic shape. Further, it is also preferable that the A site contains Pb as a main component and the B site contains one or more selected from Mg, Zn, Nb, Ni, Ti, and Zr. Furthermore, as the flux, glass having a melting point of 1000 ° C. or lower, such as lead borate glass, zinc borate glass, borosilicate glass, lead-silicate glass, zinc-silicate glass, and bismuth-silicate glass, is 0.1 wt% or more. If added, the growth form at 900 ° C. to 1300 ° C. is more likely to be a cubic shape, which is preferable. In this case, from the viewpoint of dispersibility of the glass, the glass powder is not made into a sheet as it is, but after calcination once the glass is sufficiently diffused, the calcined material is pulverized and molded using the pulverized powder. It is preferable to produce a body. When an oxide that is represented by ABO ₃ is used, it is preferable to prepare the raw material so that A / B, which is the ratio of the A site to the B site, is 1.0 or more and 1.1 or less. When A / B is in the range of 1.0 to 1.1, the aspect ratio and the degree of orientation of the crystals contained in the fired plate-like polycrystalline particles can be increased. Moreover, when A / B is in the range of 1.0 or more and 1.1 or less, it is preferable in terms of compensating for an alkali component, a lead component, or the like that volatilizes during firing. In addition, when obtaining the crystal particle 12 from the obtained fired molded body, when the A / B is in the range of 1.0 or more and 1.1 or less, the fired molded body is put in the grain boundary part when put in water. This is preferable because the existing alkali-rich phase dissolves and the crystal particles may be easily separated into individual particle units. Furthermore, when the thickness of the molded sheet is extremely thin, such as 3 μm or less, or when the atmosphere inside the sheath during baking (vapor of alkali component or lead component, etc.) is thin, the alkaline component or lead from the molded sheet during firing Since composition change due to volatilization of components and the like may be large, a range where A / B is 1.1 or more and 1.3 or less is also preferable.

  In the step of preparing the inorganic particles, it is preferable to pulverize and mix the raw materials of the inorganic particles, calcine the mixed powder, and further pulverize the obtained inorganic particles. As the raw material of the inorganic particles, oxides, hydroxides, carbonates, sulfates, nitrates, and tartrates of the target component can be used, but it is preferable to mainly use oxides and carbonates. In the pulverization of the inorganic particles, the particle size is preferably set according to the thickness of the molded body, and the median diameter (D50) of the inorganic particles is preferably 1% to 60% of the thickness of the molded body. . If the median diameter is 1% or more of the thickness of the molded body, the pulverization process is easy. If the median diameter is 60% or less, the particles in the molded body are more uniformly distributed, so that the thickness of the molded body can be easily adjusted. In order to increase the size of the crystal particles 12, it is preferable from the viewpoint of promoting grain growth to reduce the median diameter (D50) of the inorganic particles. As this particle diameter, a value measured by dispersing in a dispersion medium (such as an organic solvent or water) using a laser diffraction / scattering particle size distribution measuring apparatus is used. The inorganic particles are preferably pulverized by wet pulverization. For example, a ball mill, a bead mill, a trommel, or an attritor may be used.

(2) Molding step of the molded body The inorganic particles are molded into a self-supporting sheet-shaped molded body having a thickness of 15 μm or less. Here, the “self-supported molded body” is a sheet that can maintain the shape of the sheet-shaped molded body by itself or a sheet that cannot maintain the shape of the sheet-shaped molded body by itself. Also included are those that are attached to any substrate or formed into a film and then peeled off from this substrate before or after firing. As a method for forming the formed body, for example, a doctor blade method using a slurry containing inorganic particles, an extrusion method using a clay containing inorganic particles, or the like can be used. When using the doctor blade method, a slurry is applied to a flexible plate (for example, an organic polymer plate such as a PET film), and the applied slurry is dried and solidified to form a molded body, and the molded body and the board are peeled off. Thus, a molded body before firing the plate-like polycrystalline particles may be produced. When preparing a slurry or clay before molding, inorganic particles may be dispersed in a suitable dispersion medium, and a binder, a plasticizer, or the like may be added as appropriate. Moreover, it is preferable to prepare the slurry so that the viscosity is 500 to 700 cP, and it is preferable to defoam by reducing the pressure. The thickness of the molded body is set to 15 μm or less, more preferably 10 μm or less, further preferably 5 μm or less, and most preferably 2 μm or less. If it is 15 μm or less, a high degree of orientation of crystal grains 12 can be obtained, and if it is 10 μm or less, a higher degree of orientation of crystal grains 12 can be obtained. Moreover, it is preferable that the thickness of a molded object shall be 0.1 micrometer or more. If thickness is 0.1 micrometer or more, it will be easy to produce the self-supporting sheet-like molded object. In order to make the size of the crystal particles 12 relatively large, it is preferable that the thickness of the molded body is about 5 to 10 μm. The thickness of the sheet-like molded body is approximately the thickness of the plate-like polycrystalline particle 10 as it is, and as a result, is also related to the particle size of the crystal particle 12, so that it can be appropriately selected according to the use of the plate-like polycrystalline particle 10. Shall be set. Other molding methods include film deposition onto substrates such as resin, glass, ceramics, and metals by high-speed spraying of particles such as aerosol deposition, and vapor phase methods such as sputtering, CVD, and PVD. The molded body before firing the plate-like polycrystalline particles may be produced by peeling from the substrate. In this case, since the density of the molded body before firing can be increased, there are advantages such as grain growth at low temperature, prevention of volatilization of constituent elements, and high density of the obtained plate-like polycrystalline particles.

(3) Firing step of molded body An inactive layer (for example, a fired ceramic plate or Pt plate, a carbon plate, a graphite plate, a molybdenum plate, a non-reactive layer which does not substantially react with the molded body in the molding step) It fires in the state which adjoined the tungsten plate etc.), or it fires in the state as this molded object. For example, the molded body may be disposed and fired on a layer that is inactive at the firing temperature of the molded body, such as alumina, zirconia, spinel, carbon, graphite, molybdenum, tungsten, and platinum. Alternatively, the molded body and the inert sheet may be wound in a roll shape and fired. Or it is good also as what forms a molded object in a sheet form on an inactive layer, and makes it peel from this inactive layer after baking. Alternatively, a molded body may be formed on the inert layer, and the inert layer may be removed after firing. For example, in the case of using graphite for the inert layer, after firing in a non-oxidizing atmosphere (for example, in nitrogen) to obtain a desired fired molded body in the presence of the inert layer, an oxidizing atmosphere below that temperature ( For example, the heat treatment may be performed again in the atmosphere and the graphite may be burned to be removed. Here, even when the inorganic particles contained in the compact grow into isotropic and polyhedral crystal grains, it is considered that a specific crystal plane can be grown depending on the situation. Here, the grain growth in the thickness direction of the molded body is limited to a thickness of 15 μm or less and the grain growth is further promoted in the direction of the surface of the molded body. By growing in the plane, the aspect ratio is large and the degree of orientation is high. Thus, approximately one crystal particle 12 is present in the thickness direction of the compact.

  Moreover, it is preferable to bake a molded object in the volatilization suppression state which suppresses volatilization of the specific components (for example, alkali etc.) contained in this molded object in the baking process of a molded object. If it carries out like this, it can suppress that the composition of the plate-like polycrystal particle | grains after baking shift | deviates by suppressing that a specific element from a molded object volatilizes. For example, this molded body may be fired in a state where inorganic particles different from the molded body coexist as a volatilization-suppressed state. If it carries out like this, it can suppress that a specific component volatilizes from a molded object comparatively easily by volatilizing a specific component from the coexisting inorganic particle. At this time, “another inorganic particle” may be in the form of a powder or a molded body. Alternatively, the compact may be fired in a sealed state in a sheath with a lid as a volatilization-suppressed state. At this time, it is preferable to make the space inside the sheath as small as possible. Here, if the atmosphere inside the sheath is too thick, for example, if the amount of other inorganic particles coexisting inside the sheath is too large, sintering and grain growth of the molded body are activated, and the undulation of the molded body is increased. In some cases, grain growth may reduce the particle surface area, that is, increase the thickness, and the aspect ratio of the crystal grains may be reduced. For this reason, it is important to empirically set the volume inside the sheath, the amount of the molded body, the amount of inorganic particles to coexist, etc. to an appropriate state so that the atmosphere inside the sheath is in an optimal state. In addition, when firing with inorganic particles coexisting, it is preferable to coexist inorganic particles having the same composition as the molded body, but coexist with particles that easily volatilize a specific component than the inorganic particles constituting the molded body. The specific component can also be supplemented to the fired molded body. In the firing process, it is more important to provide an optimum atmosphere at an optimum timing. For example, firing is performed at the first firing temperature in a sheath controlled to the first atmosphere, and the temperature is returned to room temperature. Then, firing may be performed at a second firing temperature higher than the first firing temperature in the sheath controlled to the second atmosphere. The firing atmosphere may be in the air, but in terms of suppressing volatilization of constituent elements, reactivity with the inert layer, etc., in an oxygen atmosphere, a neutral atmosphere such as nitrogen, in the coexistence of hydrogen or hydrocarbons, etc. The reducing atmosphere may be in a vacuum. Further, from the viewpoint of promoting in-plane grain growth, weighted firing such as hot pressing may be performed.

  This firing process will be described with reference to the drawings. 2A and 2B are explanatory views of the firing device 20, in which FIG. 2A is a side view and FIG. 2B is a cross-sectional view taken along line AA in FIG. The firing device 20 is used when firing the molded body 30 in a firing furnace (not shown). The setter 22 is a fired ceramic plate on which the unfired molded body 30 is placed, and the molded body 30. An unfired co-fired green body 24 formed of the same inorganic particles and having a thickness greater than that of the green body 30, and a fired ceramic disposed on the co-existing green body 24 and serving as a lid for the green body 30 It is comprised by the square plate 26 which is a board. As shown in FIG. 2, by enclosing the four sides of the molded body 30 with a coexisting green molded body 24, a specific component (for example, alkali or the like) is volatilized from the molded body 30 to prevent the composition from changing. It is. Here, the setter 22 is assumed to have a flat plate shape, but a setter having a rough surface on the mounting surface of the molded body 30 or a honeycomb-shaped setter having a plurality of through holes on the mounting surface of the molded body 30; A contact area with the molded body 30 such as a dimple processed setter may be reduced to prevent the setter and the molded body 30 from being welded. Further, alumina powder or zirconia powder that is stable at the firing temperature of the molded body 30 may be placed on the mounting surface of the setter 22, and the molded body 30 may be placed and fired thereon. Here, when coexisting in a powder state inside the sheath instead of coexisting the green body, adjust the setting method and size of the setter inside the sheath, the stacking method, the position where the powder is placed, etc. Thus, the atmosphere inside the sheath can be adjusted uniformly, and when a plurality of compacts are fired, each compact can have a uniform crystal particle structure.

As for the firing conditions, the compact 30 is fired at a firing temperature at which an equilibrium crystal is obtained by firing, for example, at a temperature higher by 10% or more than the firing temperature for densification and grain growth by firing the bulk. Is preferred. At a temperature higher by 10% or more, the grain growth of the molded body 30 of 15 μm or less can be sufficiently advanced. In addition, it is preferable to bake at a high temperature so as not to decompose the material of the molded body. In particular, when the thickness of the molded body 30 becomes thinner, it becomes difficult for the grains to grow. Therefore, it is preferable to make the firing temperature higher. Further, if the size of the crystal particles 12 is to be increased, it is preferable to fire at a higher firing temperature. For example, as inorganic particles, in the firing process of LiN, K, etc. added to the A site of NaNbO ₃ and Ta added to the B site ((Li _X Na _Y K _Z ) Nb _M Ta _N O ₃ ) The body firing temperature is preferably 900 ° C. or higher and 1250 ° C. or lower. When the firing temperature is 900 ° C. or higher, the growth of particle crystals is promoted, and when the firing temperature is 1250 ° C. or lower, volatilization of alkali components and the like can be suppressed to a low level and the material can be prevented from being decomposed. By firing in this way, the inorganic particles contained in the molded body 30 grow into anisotropic crystal particles.

(4) Mesh pulverization step of fired molded body Next, the obtained fired molded body is crushed and classified. Here, it is assumed that a mesh having an opening that matches the target particle size is used, and a mesh of 1.0 mm or less is preferably used. FIG. 3 is an explanatory diagram of an example of the mesh crushing process. In this mesh pulverization step, for example, a mesh having an opening diameter of 45 μm, 25 μm, 20 μm, or the like can be used. Since the fired molded body 32 obtained by firing the molded body 30 is relatively easy to disintegrate, after placing the mesh 34 on the mesh 34, the mesh 34 is pressed while lightly pressing the fired molded body 32 with a pressing member 36 such as a spatula. The mesh grinding process can be performed by sieving. If it carries out like this, crushing of the baking molded object 32 and classification of the crushed plate-like polycrystalline particle 10 (refer FIG. 1) can be performed simultaneously in parallel. In order to obtain plate-like polycrystalline particles 10 having a larger particle size and a larger aspect ratio, the mesh openings may be enlarged, and a plate-like polycrystalline having a smaller particle size and a smaller aspect ratio. If the particles 10 are to be obtained, the mesh openings need only be made small, so that the characteristics of the plate-like polycrystalline particles 10 can be changed by a simple process of changing the size of the mesh openings. In this way, the plate-like polycrystalline particles 10 shown in FIG. 1 can be obtained.

  The obtained plate-like polycrystalline particles 10 may be used as a raw material for crystal-oriented ceramics. Then, the manufacturing method of the crystal orientation ceramics which use the plate-like polycrystalline particle 10 as a raw material is demonstrated. This crystallographically-oriented ceramic can have an arbitrary shape whose thickness direction exceeds 15 μm, for example. That is, the plate-like polycrystalline particles 10 may be produced as an intermediate product of crystal-oriented ceramics. FIG. 4 is an explanatory diagram showing an example of a method for producing a crystallographically-oriented ceramic, in which FIG. 4A is a diagram before orientation and before firing, and FIG. 4B is a diagram of a crystal-oriented ceramic 50 obtained by firing. It is. The crystal-oriented ceramic is subjected to a mixing step in which the plate-like polycrystalline particles 10, other raw material powders (for example, non-oriented inorganic particles) and the like, and a binder or a plasticizer are mixed as appropriate. It is also possible to perform a secondary molding step of molding the secondary molded body 40 (FIG. 4A) having a predetermined shape by performing orientation molding (secondary orientation) such that is oriented in a certain direction. Orientation molding can be performed by the above-described doctor blade method, extrusion molding method, or the like. Then, a secondary firing step is performed to fire this secondary compact so that other raw material powders are also oriented in the direction in which the plate-like polycrystalline particles 10 are oriented, thereby obtaining the crystal oriented ceramics 50 (FIG. 4 ( b)). The firing temperature in the secondary firing step may be a firing temperature at which the growth-type crystals are obtained under the predetermined firing conditions described above, or may be a temperature higher by 10% or more than this temperature. Thus, when the plate-like polycrystalline particles 10 are oriented in one direction and then fired, the other raw material powders grow according to the crystal orientation of the oriented plate-like polycrystalline particles 10 or are oriented plates. Since the polycrystalline particles 10 grow while taking in other raw material powders, it is possible to obtain a crystal-oriented ceramic 50 including a large number of oriented crystals 52 oriented in one direction. Even if the above-described molded body 30 is not fired in a volatilization-suppressed state when the molded body 30 is fired, the crystal-oriented ceramic 50 can be obtained by adding the components volatilized during the firing of the molded body 30 during the mixing process or the secondary molding process. The desired composition ratio can be obtained.

  According to the plate-like polycrystalline particle 10 of the present embodiment described in detail above, the inorganic particles are formed into a self-supporting sheet-like molded body having a thickness of 15 μm or less, fired, and passed through an opening of a predetermined size. Thus, since the fired compact may be crushed and classified, the aspect ratio and the degree of crystal orientation can be increased with a simpler treatment. Further, the plate-like polycrystalline particle 10 has a structure in which the crystal grains 12 are bonded to each other at the grain boundary portion 14, and is easily crushed at the grain boundary portion 14. Therefore, the grain size, the aspect ratio, and the like are easily adjusted. be able to. For this reason, as compared with the case of producing crystal-oriented ceramics using single crystal particles, the degree of orientation of the crystal-oriented ceramics 50 and the size of the oriented crystals 52 can be easily adjusted. Furthermore, since it is not necessary to add any component to enhance the orientation, plate-like polycrystalline particles having a more uniform composition can be obtained. For this reason, when the plate-like polycrystalline particles 10 are used for producing the crystal oriented ceramics 50, the crystal oriented ceramics 50 having a homogeneous composition and high orientation can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the plate-like polycrystalline particles 10 are used as a raw material for the crystallographically oriented ceramic 50, but may be used for other purposes (for example, fillers). The plate-like polycrystalline particle 10 of the present invention is composed of a dielectric material, pyroelectric material, piezoelectric material, ferroelectric material, magnetic material, ion conducting material, electron conducting material, heat conducting material, thermoelectric material, superconducting material. It can be used for a polycrystalline material made of a material whose function and characteristics such as materials and wear-resistant materials have crystal orientation dependency. Specifically, various sensors such as acceleration sensors, pyroelectric sensors, ultrasonic sensors, electric field sensors, temperature sensors, gas sensors, knocking sensors, yaw rate sensors, airbag sensors, piezoelectric gyro sensors, energy conversion elements such as piezoelectric transformers, Low-loss actuators or low-loss resonators such as piezoelectric actuators, ultrasonic motors, and resonators, capacitors, bimorph piezoelectric elements, vibration pickups, piezoelectric microphones, piezoelectric ignition elements, sonar, piezoelectric buzzers, piezoelectric speakers, oscillators, filters, dielectric elements, High performance when applied to microwave dielectric elements, thermoelectric conversion elements, pyroelectric elements, magnetoresistive elements, magnetic elements, superconducting elements, resistance elements, electron conducting elements, ion conducting elements, PTC elements, NTC elements, etc. Various elements can be obtained. At this time, the aspect ratio of the crystal particles 12 and the aspect ratio of the plate-like polycrystalline particles 10 are set appropriately according to the application. The aspect ratio and the particle size of the plate-like polycrystalline particles 10 can be easily changed simply by setting the size of the opening diameter in the mesh crushing process.

  Further, in the above-described embodiment, the plate-like polycrystalline particles 10 are arranged such that the specific crystal face 11 appears on the sheet surface (see FIG. 1), but the crystal grains 12 are two-dimensional at the grain boundary part. The crystal plane 11 may not be shown on the sheet surface as long as it is bonded.

  Below, the example which manufactured the plate-like polycrystalline particle 10 concretely is demonstrated as an experiment example.

[Experiment 1]
(Inorganic particle synthesis process)
Each powder (Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ so as to have a composition ratio of Li _0.07 (Na _0.5 K _0.5 ) _0.93 Nb _0.9 Ta _0.1 O ₃ ) Was weighed. A weighed product, zirconia balls, and ethanol as a dispersion medium were placed in a polypot, and wet mixing and pulverization were performed for 16 hours with a ball mill. The obtained slurry was dried with an evaporator and a dryer, and then pre-fired under conditions of 850 ° C. and 5 hours. This calcined powder, zirconia balls, ethanol as a dispersion medium, wet pulverized with a ball mill for 5 hours, dried with an evaporator and a dryer, and Li _0.07 (Na _0.5 K _0.5 ) _0.93 Nb _0.9 Ta _0.1 O ₃ inorganic Particle powder was obtained. When the average particle diameter of this powder was measured using a laser diffraction / scattering particle size distribution analyzer LA-750 manufactured by HORIBA using water as a dispersion medium, the median diameter (D50) was 0.6 μm.
(Molding process of self-supporting sheet-like molded product)
Into a mixture of equal amounts of toluene and isopropanol as a dispersion medium, the above inorganic particle powder, polyvinyl butyral (BM-2, manufactured by Sekisui Chemical) as a binder, a plasticizer (DOP, manufactured by Kurokin Kasei), and dispersion An agent (SP-O30, manufactured by Kao) was mixed to prepare a slurry-like forming raw material. The amount of each raw material used was 100 parts by weight of the dispersion medium, 10 parts by weight of the binder, 4 parts by weight of the plasticizer, and 2 parts by weight of the dispersant with respect to 100 parts by weight of the inorganic particles. Next, the obtained slurry was stirred and defoamed under reduced pressure to prepare a viscosity of 500 to 700 cP. The viscosity of the slurry was measured with an LVT viscometer manufactured by Brookfield. The obtained slurry was formed into a sheet on a PET film by a doctor blade method. The thickness after drying was 5 μm.
(Baking process of molded body)
A sheet-like molded body peeled off from the PET film was cut into a 50 mm square with a cutter and placed on the center of a setter (dimension 70 mm square, height 5 mm) made of zirconia. In this setter, an unsintered sheet molded body (dimensions 5 mm × 40 mm, thickness 100 μm) made of the same molding raw material as the sheet-shaped molded body is placed outside the four sides of the sheet-shaped molded body, and enclosed. A zirconia square plate (size 70 mm square, height 5 mm) was further placed thereon. Thus, the space for the sheet-like molded body was made as small as possible, and the firing conditions were set such that the same molding raw material coexisted. Then, after degreasing at 600 ° C. for 2 hours, baking was performed at 1100 ° C. for 5 hours. After firing, the part not welded to the setter was taken out.
(Mesh crushing process of fired molded product)
The obtained fired compact was placed on a 300-mesh (opening diameter 45 μm) sieve and crushed and classified while lightly pressing the fired compact with a spatula. The obtained particles were used as the plate-like polycrystalline particles of Experimental Example 1.

[Experimental Examples 2 and 3]
In the mesh crushing step, the same process as in Experimental Example 1 was performed except that the sieves were 500 mesh (opening diameter 25 μm) and 635 mesh (opening diameter 20 μm), respectively, and the obtained plate-like polycrystalline particles were tested. Examples 2 and 3 were used.

[Experimental Examples 4 to 7]
In the forming step, the same steps as in Experimental Example 1 described above were performed except that the thickness of the sheet-like molded body was 2 μm, 10 μm, 15 μm, and 20 μm. It was set to ~ 7.

[Experimental Examples 8 to 12]
In the synthesis step, the composition of the inorganic particles is Li _0.07 (Na _0.5 K _0.5 ) _0.93 NbO ₃ , Li _0.07 (Na _0.5 K _0.5 ) _0.97 NbO _3.02 , Li _0.07 (Na _0.5 K _0.5 ) _1.03 NbO _3.05 , Li _0.1 (Na _0.5 K _0.5 ) _1.1 NbO _3.1 , Li _0.07 (Na _0.5 K _0.5 ) _0.91 NbO _2.99 , that is, A / B = 1.00, 1.04, 1.10, 1.20, 0 in the general formula ABO ₃ The same procedure as in Experimental Example 2 was performed except that the inorganic particle powder was prepared so as to be .98, and the obtained plate-like polycrystalline particles were designated as Experimental Examples 8 to 12, respectively. In addition, when the average particle diameter of these experimental examples was measured in the same manner as described above, the median diameter (D50) was 0.6 μm.

[Experimental Example 13]
Experimental Example 1 in which each powder (Bi ₂ O ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Ag ₂ O, TiO ₂ ) was weighed so that the composition ratio of (Bi _0.5 Na _0.35 K _0.1 Ag _0.05 ) TiO ₃ was obtained. After wet mixing, pulverization and drying in the same manner as in Example 1, the mixture was calcined at 900 ° C. for 2 hours, and the obtained calcined powder was pulverized and dried in the same manner as in Experimental Example 1 (Bi _0.5 Na _0.35 K). _0.1 Ag _0.05 ) TiO ₃ inorganic particle powder was obtained. This powder was subjected to the same process as in Experimental Example 2 except that the thickness of the molded body was 5 μm in the molding process, and the degreasing and firing temperature was 600 ° C. for 2 hours and the firing temperature was 1250 ° C. for 3 hours in the firing process. The obtained plate-like polycrystalline particles were regarded as Experimental Example 13. In addition, when the average particle diameter of this experimental example was measured in the same manner as described above, the median diameter (D50) was 0.6 μm.

[Experimental Example 14]
In the synthesis step, ZnO—B ₂ O ₃ —SiO into a synthetic powder having a composition ratio of 0.2 Pb (Mg _0.33 Nb _0.67 ) O ₃ −0.35 PbTiO ₃ −0.45 PbZrO ₃ with 1 wt% NiO added. ₂ % glass powder (ASF1891 manufactured by Asahi Glass (AGG)) was added in an amount of 1% by weight, and this weighed product, zirconia balls, and ion-exchanged water as a dispersion medium were placed in a polypot, and wet-mixed for 16 hours with a ball mill. The obtained slurry was dried with a dryer and calcined at 800 ° C. for 2 hours. This calcined powder, zirconia balls, and ion-exchanged water as a dispersion medium were added, wet-ground by a ball mill for 5 hours, and dried by a drier to obtain inorganic particle powder. This powder was molded with a sheet thickness of 1 μm in the molding step. The obtained sheet was placed on a zirconia square plate arranged in an alumina sheath. Within this sheath, as a powder for adjusting the firing _{atmosphere, 0.2Pb (Mg 0.33 Nb 0.67)} O 3 -0.35PbTiO 3 coexist small amount of inorganic particles powder having a composition of -0.45PbZrO _3, firing In the step, except that the degreasing conditions were 600 ° C., 2 h, and the firing conditions were 1100 ° C., 5 h, the same steps as in Experimental Example 1 were performed, and the obtained plate-like polycrystalline particles were taken as Experimental Example 14. In addition, when the average particle diameter of this experimental example was measured in the same manner as described above, the median diameter (D50) was 0.6 μm.

[Experimental Example 15]
In the synthesis step, inorganic particle powder having a composition of 0.2Pb (Mg _0.33 Nb _0.67 ) O ₃ -0.35PbTiO ₃ -0.45PbZrO ₃ was used, NiO and glass powder were not added, and in the molding step, The same procedure as in Experimental Example 14 was performed except that the sheet thickness was 2 μm, and the obtained plate-like polycrystalline particles were designated as Experimental Example 14. In addition, when the average particle diameter of this experimental example was measured in the same manner as described above, the median diameter (D50) was 0.6 μm.

[Experimental Example 16]
The same process as in Experimental Example 14 was performed except that the A / B ratio of Experimental Example 14 to 0.2Pb (Mg _0.33 Nb _0.67 ) O ₃ −0.35 PbTiO ₃ −0.45 PbZrO ₃ was 1.1. The obtained plate-like polycrystalline particles were regarded as Experimental Example 16.

[Electron micrograph]
About the said Experimental Examples 1-14, the SEM photograph was image | photographed using the scanning electron microscope (JEOL JSM-6390). First, SEM observation is performed in a state where plate-like polycrystalline particles are randomly arranged on a conductive tape using a spoon, in which the sheet surface is parallel to the observation direction, that is, vertically The standing powder was selected and the thickness Z of the crystal particles 12 was determined. Next, a solution obtained by adding 0.1 g of plate-like polycrystalline particles to 2 g of ethanol was dispersed for 30 minutes with an ultrasonic disperser (ultrasonic cleaner), and this was spin-coated on a glass substrate at 2000 rpm to obtain a plate-like shape. SEM observation was performed by arranging the crystal grains so as not to overlap as much as possible and in a state where the crystal plane and the substrate plane were parallel. Among them, in a visual field including about 20 to 40 crystal grains, the crystal plane of the plate-like polycrystalline particles is observed, the longest length X of the crystal plane 11 of the crystal grains 12 is obtained, and the longest length of the crystal plane 11 is obtained. The thickness X is assumed to be the particle size of the crystal particle 12, and the particle size is divided by the thickness Z of the crystal particle 12 to calculate the aspect ratio of each crystal particle 12, and the average value is calculated as the plate-like polycrystalline particle 10 The aspect ratio of the crystal grains 12 contained in Similarly, the thickness W of the plate-like polycrystalline particles 10 is obtained from the SEM photograph, and the crystal plane of the plate-like polycrystalline particles 10 is observed in a field of view containing about 5 to 30 plate-like polycrystalline particles 10. Then, the longest length Y of the plate-like polycrystalline particles 10 is obtained, the longest length Y is assumed to be the particle size of the plate-like polycrystalline particles 10, and this particle size is divided by the thickness W of the plate-like polycrystalline particles 10. The aspect ratio of each plate-like polycrystalline particle 10 was calculated, and the average value was calculated as the aspect ratio of the plate-like polycrystalline particle 10.

[Orientation]
About the said Experimental Examples 1-14, the XRD diffraction pattern when irradiating the X-ray with respect to the surface of the plate-like polycrystalline particle 10 was measured using the XRD diffractometer (RAD-IB by Rigaku Corporation), and the Lotgering method The degree of orientation of the pseudocubic (100) plane was calculated using the above formula (1) using the peaks of the pseudocubic (100), (110), and (111). In XRD diffraction measurement, 0.1 g of plate-like polycrystalline particles added to 2 g of ethanol was dispersed for 30 minutes with an ultrasonic disperser (ultrasonic cleaner), and this was dispersed on a 25 mm × 50 mm glass substrate at 2000 rpm. The coating was performed by spin coating so that the plate-like polycrystalline particles were not overlapped as much as possible and the crystal plane and the glass substrate surface were parallel.

  The evaluation results of Experimental Examples 1 to 16 thus obtained are shown in Table 1 and FIGS. Table 1 shows sample name, inorganic material, firing temperature, thickness of plate-like polycrystalline particle 10, mesh opening diameter, aspect ratio of crystal particle 12, range of size of crystal particle 12, plate-like polycrystalline particle 10 The aspect ratio, the size range of the plate-like polycrystalline particles 10, and the degree of orientation of the plate-like polycrystalline particles 10 were shown. FIG. 5 is an X-ray diffraction pattern of Experimental Example 2, and FIGS. 6 to 8 are SEM photographs of Experimental Examples 1-3. In addition, this SEM photograph showed what arrange | positioned the plate-like polycrystalline particle on the glass substrate at random. According to the result of this example, as shown in FIG. 5, since the peak attributed to the (100) plane is large, the plate-like polycrystalline particle 10 of the present invention has a plurality of (100) planes on the sheet surface. It can be seen that it is composed of crystal grains. As shown in FIGS. 6 to 8, the plate-like polycrystalline particle 10 includes a plurality of crystal particles having a specific crystal face, and a portion having one crystal particle in the thickness direction occupies a wide range, and the plurality of crystals It was observed that the particles 12 were bonded at the grain boundary portion with a specific crystal plane aligned. For this reason, it was found that the plate-like polycrystalline particles can be crushed relatively easily at the grain boundary where the crystal particles are bonded to each other. That is, according to Experimental Examples 1 to 3, it was found that the aspect ratio and size of the plate-like polycrystalline particles can be easily changed by changing the mesh opening diameter. Further, as shown in Table 1, it was found that the degree of orientation and the aspect ratio of the crystal particles 12 can be changed by changing the thickness and A / B value of the plate-like polycrystalline particles 10. In addition, according to Experimental Examples 2, 8 to 12, 14, and 16, it was found that A / B is more preferably in the range of 1.0 to 1.2. As shown in Table 1, from the results of Experimental Examples 1 and 4 to 7, it was found that the degree of orientation was improved when the thickness of the plate-like polycrystalline particles 10 was 15 μm or less. In Experimental Examples 7 and 12, one crystal particle was not substantially formed in the thickness direction.

[Production of crystal-oriented ceramics]
Inorganic particles after calcination of Experimental Example 1 so that the composition of the crystal-oriented ceramic after firing is equal to Li _0.03 Na _0.475 K _0.475 Nb _0.82 Ta _0.18 O ₃ in a mixture of equal amounts of toluene and isopropanol as a dispersion medium Powder (unoriented raw material powder), plate-like polycrystalline particles 10 of Experimental Example 1, polyvinyl butyral (BM-2, manufactured by Sekisui Chemical) as a binder, and plasticizer (DOP, manufactured by Kurokin Kasei) And a dispersant (SP-O30, manufactured by Kao Corporation) were mixed to prepare a slurry-like molding raw material. The amount of each raw material used was 30 parts by weight of plate-like polycrystalline particles, 100 parts by weight of a dispersion medium, 10 parts by weight of a binder, 4 parts by weight of a plasticizer, and 2 parts by weight of a dispersant with respect to 100 parts by weight of an inorganic material. Next, the obtained slurry was stirred and defoamed under reduced pressure to prepare a viscosity of 2500 to 3000 cP. The viscosity of the slurry was measured with an LVT viscometer manufactured by Brookfield. The obtained slurry was formed into a flat plate shape by a doctor blade method so that the plate-like polycrystalline particles 10 were oriented in one direction and the thickness after drying was 100 μm. The flat plate was dried at room temperature, degreased at 600 ° C. for 2 hours, and then fired at 1100 ° C. for 5 hours to grow grains of the inorganic material powder.

  The present invention can be used in the field of manufacturing ceramics with oriented crystals.

2 is an explanatory diagram illustrating an example of plate-like polycrystalline particles 10. FIG. It is explanatory drawing of the baking machine 20, FIG. 2 (a) is a side view, FIG.2 (b) is AA sectional drawing of (a). It is explanatory drawing of an example of a mesh grinding | pulverization process. It is explanatory drawing showing an example of the manufacturing method of the crystal orientation ceramics. 7 is an X-ray diffraction pattern of Experimental Example 4. 3 is a SEM photograph of Experimental Example 1. 4 is a SEM photograph of Experimental Example 2. 4 is a SEM photograph of Experimental Example 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Plate-like polycrystal particle | grains, 11 crystal face, 12 crystal grain | grains, 14 grain boundary part, 20 baking machine, 22 setter, 24 unsintered molded object for coexistence, 26 square plate, 30 molded object, 32 baked molded object, 34 mesh , 36 pressing member, 40 secondary compact, 50 crystal oriented ceramics, 52 oriented crystal.

Claims (25)

Including a plurality of crystal grains,
There is substantially one crystal grain in the thickness direction, and the plurality of crystal grains are bonded at the grain boundary portion in a state where specific crystal faces are aligned.
Plate-like polycrystalline particles.   The plate-like polycrystalline particle according to claim 1, wherein the crystalline particle is composed of inorganic particles that grow into isotropic and polyhedral crystalline particles and has a specific crystal face.   The plate-like polycrystalline particle according to claim 1 or 2, wherein the plate-like polycrystalline particle has an aspect ratio of 2 or more.   The plate-like polycrystalline particle according to any one of claims 1 to 3, wherein the degree of orientation of the plate-like polycrystalline particle is 25% or more by the Lotgering method.   The plate shape according to any one of claims 1 to 4, wherein the crystal particle has a length of the crystal particle in a plane direction of the plate-like polycrystalline particle that is equal to or longer than a length in a thickness direction of the crystal particle. Polycrystalline particles.   The plate-like polycrystalline particle according to any one of claims 1 to 5, wherein a thickness of the crystal particle is 0.1 µm or more and 15 µm or less.   The plate-like polycrystalline particle according to any one of claims 1 to 6, wherein the crystal particle is composed of inorganic particles that grow into anisotropic crystal particles. The crystal grains are mainly composed of an oxide represented by the general formula ABO ₃ , the A site includes one or more selected from Li, Na, K, Bi and Ag, and the B site is composed of Nb, Ta and Ti. The plate-like polycrystalline particle according to any one of claims 1 to 7, which is a particle containing one or more kinds selected. The crystal grains are mainly composed of an oxide represented by the general formula ABO ₃ , the A site contains Pb, and the B site contains one or more selected from Mg, Zn, Nb, Ni, Ti and Zr. The plate-like polycrystalline particles according to any one of claims 1 to 7, wherein   The plate-like polycrystalline particles according to claim 8 or 9, wherein the crystal particles have an A / B ratio before firing, which is a ratio of the A site to the B site, of 1.0 or more and 1.3 or less.   The plate-like polycrystalline particle according to any one of claims 1 to 10, wherein the crystal particle is composed of an oxide having a perovskite structure. A method for producing plate-like polycrystalline particles containing a plurality of crystal particles,
A molding step of molding the inorganic particles into a self-supporting sheet-like molded body having a thickness of 15 μm or less;
A firing step of firing placed on an inert layer that does not react with the green body in the molded product substantially,
A pulverizing step of pulverizing and classifying the fired compact by passing through an opening of a predetermined size;
A method for producing plate-like polycrystalline particles comprising   13. The method for producing plate-like polycrystalline particles according to claim 12, wherein the forming step uses inorganic particles that grow into isotropic and polyhedral crystal grains under predetermined firing conditions.   13. The method for producing plate-like polycrystalline particles according to claim 12, wherein the forming step uses inorganic particles that grow into anisotropic crystal particles under predetermined firing conditions. In the molding step, the oxide represented by the general formula ABO ₃ is a main component, the A site includes one or more selected from Li, Na, K, Bi and Ag, and the B site is composed of Nb, Ta and Ti. The manufacturing method of the plate-shaped polycrystalline particle of any one of Claims 12-14 using the inorganic particle used as the oxide containing 1 or more types chosen. In the molding step, the oxide A site represented by the general formula ABO ₃ contains one or more selected from Li, Na and K, and the B site contains one or more selected from Nb and Ta; Using inorganic particles
In the firing step, the firing temperature of the molded body is 900 ° C. or more and 1250 ° C. or less.
The method for producing plate-like polycrystalline particles according to claim 15. In the molding step, an oxide containing the oxide represented by the general formula ABO ₃ as a main component, the A site containing Pb, and the B site containing one or more selected from Mg, Zn, Nb, Ni, Ti and Zr. The manufacturing method of the plate-like polycrystalline particle of any one of Claims 12-14 using the inorganic particle used as a thing.   The said shaping | molding process uses the inorganic particle of the oxide whose A / B which is ratio of the said A site and B site is 1.0 or more and 1.3 or less, It is any one of Claims 15-17 A method for producing plate-like polycrystalline particles.   The method for producing plate-like polycrystalline particles according to any one of claims 12 to 18, wherein inorganic particles having a perovskite structure are used in the molding step.   The plate according to any one of claims 12 to 19, wherein, in the molding step, the molded body is molded using the inorganic particles having a median diameter of 1% to 60% of the thickness of the molded body. For producing granular polycrystalline particles.   The method for producing plate-like polycrystalline particles according to any one of claims 12 to 20, wherein, in the firing step, the shaped body is fired in a volatilization-suppressed state that suppresses volatilization of a specific component contained in the shaped body. .   The method for producing plate-like polycrystalline particles according to claim 21, wherein in the firing step, the compact is fired in a state where the inorganic particles different from the compact are coexisting as the volatilization-suppressed state.   The plate shape according to any one of claims 12 to 22, wherein in the pulverization step, the fired formed body is crushed and classified by passing an opening having a predetermined size of 1.0 mm or less. A method for producing polycrystalline particles.   24. The pulverizing step, wherein the fired molded body is pressed by a pressing member to pass through the mesh having the opening of the predetermined size, and the fired molded body is crushed and classified. A method for producing plate-like polycrystalline particles according to claim 1. A mixing step of mixing the plate-like polycrystalline particles according to any one of claims 1 to 11 and a raw material powder;
A second forming step of orienting the plate-like polycrystalline particles in a predetermined direction in the mixed powder to form a predetermined secondary compact;
A second firing step of firing the secondary molded body so as to orient the raw material powder in a direction in which the plate-like polycrystalline particles are oriented;
The manufacturing method of the crystal orientation ceramics containing this.