JP2006124251A - Method for producing crystal-oriented ceramic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a crystal-oriented ceramic, by which the piezoelectric and dielectric characteristics of the crystal-oriented ceramic can be easily controlled. <P>SOLUTION: The method is useful for producing the crystal-oriented ceramic which includes an isotropic perovskite-type compound as a main phase and in which a specific crystal surface A of each crystal grain constituting a polycrystalline body is oriented. In the method, a preparing process, a pulverizing process, a mixing process, a forming process and a firing process are carried out. In the preparing process, a first anisotropic-shape powder having an orientation plane lattice-matching with the crystal surface A is prepared. In the pulverizing process, the first anisotropic-shape powder is pulverized. In the mixing process, the pulverized first anisotropic-shape powder is mixed with a fine powder forming the isotropic perovskite-type compound when it is sintered together with the first anisotropic-shape powder. In the forming process, the obtained mixed powder is formed so that the orientation plane of the first anisotropic-shape powder is oriented to nearly same direction. In the firing process, the first anisotropic-shape powder and the fine powder are sintered. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, in which specific crystal planes of crystal grains constituting the polycrystal are oriented.

  Piezoelectric materials are materials that have a piezoelectric effect, and their forms are classified into single crystals, ceramics, thin films, polymers, and composites (composites). Among these piezoelectric materials, in particular, piezoelectric ceramics are widely applied in the fields of electronics and mechatronics because they have high performance, a large degree of freedom in shape, and material design is relatively easy.

  Piezoelectric ceramics have been subjected to so-called polarization treatment in which an electric field is applied to ferroelectric ceramics to align the direction of the domain of the ferroelectric material in a certain direction. In piezoelectric ceramics, an isotropic perovskite-type crystal structure in which the direction of spontaneous polarization can be taken three-dimensionally is advantageous in order to align spontaneous polarization in a certain direction by polarization treatment. For this reason, most of the piezoelectric ceramics in practical use are isotropic perovskite ferroelectric ceramics.

As the isotropic perovskite type ferroelectric ceramic, for example, Pb (Zr · Ti) O ₃ (hereinafter referred to as “PZT”), PZT3 in which lead-based composite perovskite is added as a third component to PZT. Component systems such as BaTiO ₃ , Bi _0.5 Na _0.5 TiO ₃ (hereinafter referred to as “BNT”) are known.

  Among these, lead-based piezoelectric ceramics represented by PZT have higher piezoelectric properties than other piezoelectric ceramics, and occupy most of the piezoelectric ceramics currently in practical use. However, since lead oxide (PbO) having a high vapor pressure is included, there is a problem that the load on the environment is large. Therefore, there is a demand for piezoelectric ceramics that have low or no lead and have piezoelectric properties equivalent to PZT.

On the other hand, BaTiO ₃ ceramics has a relatively high piezoelectric property among piezoelectric materials not containing lead, and is used for sonar. Among solid solutions of BaTiO ₃ and other lead-free perovskite compounds (for example, BNT), those showing relatively high piezoelectric properties are known. However, these lead-free piezoelectric ceramics have a problem that the piezoelectric characteristics are low as compared with PZT.

In order to solve this problem, various proposals have been conventionally made.
For example, there are isotropic perovskite-type potassium sodium niobate niobates exhibiting relatively high piezoelectric properties among non-lead-based materials and piezoelectric ceramics made of a solid solution thereof (Patent Documents 1 to 6).
However, these lead-free piezoelectric ceramics have a problem that they cannot yet exhibit sufficient piezoelectric characteristics as compared with PZT-based piezoelectric ceramics.

In such a background, a piezoelectric element having a piezoelectric ceramic including ceramic crystal grains having shape anisotropy and having spontaneous polarization preferentially oriented in one plane is disclosed (see Patent Document 7).
It is known that the piezoelectric properties and the like of isotropic perovskite compounds generally vary depending on the direction of the crystal axis. Therefore, if high crystal axes such as piezoelectric characteristics can be oriented in a certain direction, the anisotropy of piezoelectric characteristics can be utilized to the maximum, and high performance of piezoelectric ceramics can be expected. In fact, it is known that some single crystals made of lead-free ferroelectric materials exhibit excellent piezoelectric characteristics. However, single crystals have a problem of high manufacturing costs. In addition, a solid solution single crystal having a complicated composition is likely to cause a deviation in composition at the time of manufacture, and is unsuitable as a practical material. Further, a single crystal has a characteristic that it is easily broken when stress is applied. Therefore, the use under high stress is difficult and there is a problem that the application range is limited.
As disclosed in Patent Document 7, according to the method of orienting a specific crystal plane using a plate-like powder having a predetermined composition as a reactive template, the crystal orientation in which the specific crystal plane is oriented with a high degree of orientation Ceramics can be manufactured easily and inexpensively, and lead-free piezoelectric ceramics having excellent piezoelectric characteristics can be obtained.

The crystal-oriented ceramic can exhibit various piezoelectric characteristics, dielectric characteristics, and temperature characteristics depending on its composition and the like. However, it is difficult to improve all of the piezoelectric characteristics, dielectric characteristics, temperature characteristics, etc. of the crystal oriented ceramics by changing the composition. That is, generally, when one of the piezoelectric characteristics and the temperature characteristics is intensively improved by changing the composition of the crystal-oriented ceramics, the other characteristics often decrease.
Further, the crystal oriented ceramics are required to have different temperature characteristics, dielectric characteristics, piezoelectric characteristics, etc. depending on the product in which the crystal oriented ceramics are used. Therefore, it has been desired to develop a method that can easily control the characteristics of crystallographically-oriented ceramics.
However, in the conventional method of changing the composition of the crystal orientation ceramics, a huge number of samples are prepared by changing the type and blending ratio of the crystal orientation ceramic raw material, and the characteristics of each sample are evaluated. Thus, it was necessary to find a sample having the desired characteristics. Therefore, a great deal of time and labor is required for sample adjustment and evaluation, and it has been difficult to adapt flexibly to diversifying product applications.

JP 2000-313664 A Japanese Patent Laid-Open No. 2003-300776 JP 2003-306479 A JP 2003-327472 A JP 2003-342069 A JP 2003-342071 A JP 2004-7406 A

  The present invention has been made in view of such conventional problems, and provides a method for producing a crystallographically-oriented ceramic capable of easily controlling properties such as piezoelectric properties, dielectric properties, and temperature properties of crystal-oriented ceramics. It is something to try.

A first invention is a method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, and a specific crystal plane A of the crystal grains constituting the polycrystal is oriented. ,
A preparatory step of preparing a first anisotropic shaped powder comprising first oriented particles comprising a perovskite type compound and having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented;
A pulverizing step of pulverizing the first anisotropic shaped powder with a jet mill;
Fine powder having an average particle size of 1/3 or less of the first anisotropically shaped powder after the pulverization step and producing the isotropic perovskite type compound by sintering together with the first anisotropically shaped powder Preparing a raw material mixture by mixing the fine powder and the first anisotropic shaped powder,
A molding step of molding the raw material mixture to produce a molded body so that the orientation planes of the first anisotropic shaped powder are oriented in substantially the same direction;
A method for producing a crystallographically-oriented ceramic, comprising the step of heating the shaped body and sintering the first anisotropically shaped powder and the fine powder.

In the manufacturing method of the first invention, as described above, the preparation step, the pulverization step, the mixing step, the forming step, and the firing step are performed.
In the preparatory step, a first anisotropic shaped powder is prepared which is made of a perovskite type compound and includes first oriented particles having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented. .
In the mixing step, the first anisotropic shaped powder and the fine powder are mixed to prepare a raw material mixture. In the molding step, the raw material mixture is molded such that the orientation planes of the first anisotropic shaped powder are oriented in substantially the same direction.
The first oriented particles constituting the first anisotropic shaped powder have a specific crystal plane (orientation plane) oriented, and in the molding step, as described above, the orientation of the first oriented particles. The raw material mixture is formed so that the surfaces are oriented in substantially the same direction. That is, in the molding step, the raw material mixed powder is shaped so that a force acts on the first anisotropic shaped powder from one direction, for example, to thereby apply shear to the first anisotropic shaped powder. The first anisotropic shaped powder can be oriented in the molded body by stress or the like.

In the firing step, the compact is heated to sinter the first anisotropic shaped powder and the fine powder. As described above, when the formed body in which the first anisotropically shaped powder is oriented is sintered, an anisotropically shaped crystal composed of an isotropic perovskite compound that inherits the orientation direction of the anisotropically shaped powder is generated. Can do. As a result, the above-mentioned crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase and having a specific crystal plane A of the crystal grains constituting the polycrystal is oriented can be produced.
In the present invention, the orientation plane of the first oriented particles has lattice matching with the specific crystal plane A of the crystal grains constituting the polycrystal to be produced. Yes. Therefore, in the firing step, the first anisotropic shaped powder functions as a template or a reactive template, and the oriented surface of the first oriented particles forms the above-mentioned isotropic perovskite compound generated after sintering. It is inherited as a specific crystal plane A. Therefore, as described above, an isotropic perovskite compound can be produced in a state where the specific crystal plane A is oriented in one direction. Moreover, in the said baking process, while producing the said isotropic perovskite type compound, it can sinter and can manufacture the said polycrystal. In this way, the above-mentioned crystallographically oriented ceramic can be obtained.

The production method of the present invention includes the pulverization step, and the first anisotropic shaped powder is pulverized by a jet mill in the pulverization step.
Therefore, in the pulverization step, the shape and size (particle size) of the first oriented particles can be controlled to a desired shape and size. As a result, piezoelectric properties such as piezoelectric d ₃₁ constant, electromechanical coupling coefficient Kp, piezoelectric g ₃₁ constant, etc. of the crystal-oriented ceramic obtained without changing the composition of the raw materials such as the first anisotropically shaped powder, relative permittivity Dielectric characteristics such as ε _33T / ε ₀ , dielectric loss tan δ, etc., and temperature dependence of piezoelectric characteristics and dielectric characteristics, that is, temperature characteristics can be easily changed.

  In particular, in the present invention, the first anisotropic shaped powder is pulverized by a jet mill. Therefore, in the pulverization step, the first anisotropic shaped powder can be pulverized by causing particles to collide with each other in a high-speed swirling airflow of a jet mill. In addition, since centrifugal force acts on the first anisotropically shaped powder in the high-speed swirling airflow of the jet mill, the first anisotropically shaped powder that has been pulverized to a predetermined size is selectively removed from the pulverizer of the jet mill. It can be discharged. That is, the first anisotropic shaped powder is prevented from staying in the pulverizer and being excessively pulverized, and the first anisotropic shaped powder can be easily controlled to a desired size. Furthermore, even after pulverization, the first anisotropic shaped powder having a sharp particle size distribution and little size variation can be obtained.

In addition, by performing pulverization with a jet mill, it is possible to pulverize to a predetermined size in a short time, and therefore, it is possible to prevent the first anisotropically shaped powder from being rounded and changing its shape. it can. That is, it can grind | pulverize in the state which maintained the anisotropic shape of the said 1st anisotropic shaped powder prepared in the said preparation process.
Further, as described above, since the particles can be pulverized by mutual collision between particles, contamination of metal elements and the like is less likely to occur than, for example, pulverization by a ball mill or the like.

  As described above, according to the manufacturing method of the first aspect of the invention, a specific crystal plane is oriented with a high degree of orientation, and crystal oriented ceramics having excellent piezoelectric characteristics and temperature characteristics can be manufactured and obtained. Characteristics such as piezoelectric characteristics, dielectric characteristics, and temperature characteristics of the crystal oriented ceramics can be easily controlled.

A second invention is a method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, and a specific crystal plane A of the crystal grains constituting the polycrystal is oriented. ,
A preparatory step of preparing a first anisotropic shaped powder comprising first oriented particles comprising a perovskite type compound and having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented;
Preparing a fine powder having an average particle size of 1/3 or less of the first anisotropic shaped powder and producing the isotropic perovskite compound by sintering together with the first anisotropic shaped powder; A mixing step of mixing the fine powder and the first anisotropically shaped powder to produce a raw material mixture;
A molding step of molding the raw material mixture to produce a molded body so that the crystal planes of the first anisotropic shaped powder are oriented in substantially the same direction;
A heating step of heating the molded body and sintering the first anisotropic shaped powder and the fine powder;
In the preparation step, a second anisotropic shaped powder is prepared which is made of a layered perovskite type compound, and whose crystal face with the smallest surface energy is made of second oriented particles having lattice matching with the oriented surface of the first oriented particles. And preparing a reaction raw material for producing the first anisotropically shaped powder by reacting with the second anisotropically shaped powder after the grinding process of grinding the second anisotropically shaped powder with a jet mill The first anisotropic shaped powder is prepared by performing a heat treatment process for producing the first anisotropic shaped powder by heating the reaction raw material and the second anisotropic shaped powder in a flux. The present invention resides in a method for producing a crystallographically-oriented ceramic (claim 3).

In the said 2nd invention, the said preparatory process, the said mixing process, the said shaping | molding process, and the said baking process are performed.
Also in the second invention, similarly to the first invention, by preparing the first anisotropic shaped powder in the preparation step, and further performing the mixing step, the molding step, and the firing step, A crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, in which a specific crystal plane A of the crystal grains is oriented, can be produced.

In the preparation step, the first anisotropic shaped powder is prepared by performing the pulverization process and the heat treatment process.
In the pulverization process, a second anisotropic shaped powder comprising a layered perovskite compound and having a crystal plane having the smallest surface energy and comprising second oriented particles having lattice matching with the oriented surface of the first oriented particles is prepared. Then, the second anisotropic shaped powder is pulverized. In the heat treatment step, the first anisotropic shaped powder is produced by heating the second anisotropic shaped powder and the reaction raw material in a flux.
Thus, the said 1st anisotropic shaped powder is produced from the said 2nd anisotropic shaped powder and the said reaction raw material by performing the said grinding | pulverization process and the said heat processing process. Therefore, even if the first anisotropically shaped powder has a composition with extremely small anisotropy of the crystal lattice and has a composition that is difficult to produce by synthesis of a normal oxide, The first anisotropically shaped powder having an orientation surface can be easily produced.

In the pulverization process, the second anisotropic shaped powder is pulverized by a jet mill.
Therefore, in the pulverization process, the second oriented particles can be controlled to have a desired shape and size (particle size). Therefore, in the heat treatment process, the shape and size of the first anisotropic shaped powder obtained by reacting the second anisotropic shaped powder and the reaction raw material can be easily changed. As a result, without changing the composition of the first anisotropically shaped powder or the crystal-oriented ceramic, the piezoelectric properties such as piezoelectric d ₃₁ constant, electromechanical coupling coefficient Kp, piezoelectric g ₃₁ constant, etc. Dielectric characteristics such as dielectric constant ε _33T / ε ₀ , dielectric loss tan δ, etc., and temperature dependence of piezoelectric characteristics and dielectric characteristics, that is, temperature characteristics can be easily changed.

  In particular, in the present invention, the second anisotropic shaped powder is pulverized by a jet mill. Therefore, in the pulverization process, the second anisotropic shaped powder can be pulverized by causing particles to collide with each other in a high-speed swirling airflow of a jet mill. In addition, since centrifugal force acts on the second anisotropically shaped powder in the high-speed swirling airflow of the jet mill, the second anisotropically shaped powder pulverized to a predetermined size is selectively removed from the pulverizer of the jet mill. It can be discharged. That is, it is possible to prevent the second anisotropic shaped powder from staying in the pulverizer and being excessively pulverized, and to easily control the second anisotropic shaped powder to a desired size. Furthermore, the second anisotropic shaped powder with a sharp particle size distribution and little size variation can be obtained even after pulverization.

In addition, since it can be pulverized to a predetermined size in a short time by pulverizing with a jet mill, it is possible to prevent the second anisotropically shaped powder from being rounded and changing its shape. it can. That is, it can grind | pulverize in the state which maintained the anisotropic shape of the said 2nd anisotropic shaped powder prepared in the said preparation process.
Further, as described above, since the particles can be pulverized by mutual collision between particles, contamination of metal elements and the like is less likely to occur than, for example, pulverization by a ball mill or the like.
Other functions and effects are the same as those of the first invention.

  Therefore, according to the manufacturing method of the second aspect of the invention, a specific crystal plane is oriented with a high degree of orientation, and crystal oriented ceramics having excellent piezoelectric characteristics and temperature characteristics can be produced, and the obtained crystal orientation Characteristics such as piezoelectric characteristics and temperature characteristics of ceramics can be easily controlled.

Hereinafter, embodiments of the present invention will be described.
In the production method of the present invention, a crystal-oriented ceramic comprising a polycrystal having an isotropic perovskite-type compound as a main phase and having a specific crystal plane A of the crystal grains constituting the polycrystal is oriented. Can do.
Such grain oriented ceramics, for example, the general formula (3): {Lix (K 1-y Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 ( where, 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0) and the main phase is an isotropic perovskite compound.

In the crystal-oriented ceramic, the specific crystal plane A of the crystal grains constituting the polycrystal of the crystal-oriented ceramic is oriented.
“Specific crystal plane A is oriented” means that each crystal grain is aligned so that specific crystal planes A of an isotropic perovskite compound such as a compound represented by the general formula (3) are parallel to each other. Are arranged (hereinafter, this state is referred to as “plane orientation”), or each crystal so that a specific crystal plane A is parallel to one axis penetrating the polycrystal. It means both that the grains are arranged (hereinafter, such a state is referred to as “axial orientation”).

  As the type of the crystal plane A that is oriented, for example, depending on the direction of spontaneous polarization of the isotropic perovskite compound such as the compound represented by the general formula (3), the use of the crystal-oriented ceramic, the required characteristics, etc. You can choose. That is, the crystal plane A can be selected according to the purpose, such as a pseudo-cubic {100} plane, a pseudo-cubic {110} plane, or a pseudo-cubic {111} plane.

“Pseudocubic {HKL}” is generally an isotropic perovskite type compound that has a slightly distorted structure from cubic, such as tetragonal, orthorhombic, and trigonal crystals, but the distortion is slight. This means that it is regarded as a cubic crystal and displayed by Miller index.
Further, when the specific crystal plane A is plane-oriented, the degree of plane orientation can be expressed by the average degree of orientation F (HKL) by the Lotgering method expressed by the following equation (1). it can.

In Equation 1, ΣI (hkl) is the sum of X-ray diffraction intensities of all crystal planes (hkl) measured for the crystallographic ceramics, and ΣI ₀ (hkl) has the same composition as the crystallographic ceramics. It is the sum total of the X-ray diffraction intensities of all crystal planes (hkl) measured with respect to the non-oriented piezoelectric ceramic. Σ′I (HKL) is the sum of X-ray diffraction intensities of crystallographically equivalent specific crystal planes (HKL) measured for crystal-oriented ceramics, and Σ′I ₀ (HKL) is the crystal It is the sum total of X-ray diffraction intensities of specific crystal planes (HKL) that are crystallographically equivalent measured for non-oriented piezoelectric ceramics having the same composition as oriented ceramics.

  Therefore, when the crystal grains constituting the polycrystal are non-oriented, the average degree of orientation F (HKL) is 0%. Further, when the (HKL) planes of all the crystal grains constituting the polycrystal are oriented parallel to the measurement plane, the average degree of orientation F (HKL) is 100%.

In the above-mentioned crystallographically-oriented ceramic, higher properties are obtained as the proportion of oriented crystal grains increases. For example, when plane orientation is performed on a specific crystal plane, in order to obtain high piezoelectric characteristics and the like, the average orientation degree F (HKL) by the Lotgering method represented by the formula 1 is 30% or more. It is preferable. More preferably, it is 50% or more. The specific crystal plane to be oriented is preferably a plane perpendicular to the polarization axis. Further, when the crystal system of the perovskite compound is tetragonal, the specific crystal plane A to be oriented is preferably a pseudo-cubic {100} plane.
Therefore, the polycrystal preferably has a pseudo cubic {100} plane orientation degree of 30% or more by the Lotgering method (claim 10).

  When the specific crystal plane A is axially oriented, the degree of orientation cannot be defined by the same degree of orientation (formula 1) as the plane orientation. However, using the average orientation degree (hereinafter referred to as “axial orientation degree”) according to the Lotgering method for (HKL) diffraction when X-ray diffraction is performed on a plane perpendicular to the orientation axis, Can be expressed. In addition, the degree of axial orientation of the polycrystal body in which the specific crystal plane A is almost completely axially oriented is the axis orientation degree measured for the polycrystal body in which the specific crystal plane is almost completely plane-oriented A. It becomes the same level.

  Since the crystal-oriented ceramic is made of a polycrystal having the isotropic perovskite compound as a main phase, it can exhibit high piezoelectric characteristics and the like among non-lead-based piezoelectric ceramics. In addition, since the above-mentioned crystal-oriented ceramic has a specific crystal plane of each crystal grain constituting the polycrystalline body oriented in one direction, it has higher piezoelectric properties than the non-oriented sintered body having the same composition. Can be shown.

Specifically, the piezoelectric d ₃₁ at room temperature is optimized by optimizing the composition, degree of orientation, production conditions and the like of the isotropic perovskite type compound such as the compound represented by the general formula (3) constituting the main phase. A crystallographically-oriented ceramic whose constant is at least 1.1 times that of the non-oriented sintered body having the same composition is obtained. Further, if these conditions are optimized, crystal oriented ceramics whose piezoelectric d ₃₁ constant at room temperature is 1.2 times or more that of a non-oriented sintered body having the same composition, and further optimized is 1.3 times or more. can get.

Ceramics composed of isotropic perovskite type compounds having a complex composition such as the compound represented by the general formula (3) usually have a simple compound containing component elements in a desired stoichiometric ratio. It is produced by a method of mixing, molding and calcining the mixture, crushing, and then remolding and sintering the crushed powder. However, with such a method, it is extremely difficult to produce the above-mentioned crystallographically-oriented ceramic in which specific crystal planes of crystal grains are oriented in a specific direction.
In the present invention, as described above, the first anisotropically shaped powder that satisfies the specific condition is oriented in the molded body, and the first anisotropically shaped powder is used as a template or a reactive template to formula (3). The isotropic perovskite compound such as the compound represented by formula (1) is synthesized and sintered, whereby specific crystal planes of crystal grains constituting the polycrystal are oriented in one direction.

In the production method of the present invention, the first anisotropic shaped powder is prepared in the preparation step.
First, the first anisotropic shaped powder will be described.
The first anisotropically shaped powder is made of a perovskite type compound, and has an orientation plane formed by orienting a crystal plane having lattice matching with a specific crystal plane A of the crystal grain in the polycrystal to be produced. It consists of first oriented particles.

The lattice matching can be expressed by a lattice matching rate.
In describing the lattice matching, for example, the case where the first oriented particles are metal oxides will be described. That is, in the two-dimensional crystal lattice of the orientation plane in the first oriented particles, for example, a two-dimensional lattice point of oxygen atoms or a lattice point of metal atoms and the specific crystal plane A oriented in the polycrystal. In the case where a lattice point composed of oxygen atoms or a lattice point composed of metal atoms in the crystal lattice has a similar relationship, lattice matching exists between them.
The lattice matching rate is the absolute value of the difference between the orientation plane of the first oriented particles and the lattice size at the similar position of the specific crystal plane A oriented in the polycrystalline body. The value obtained by dividing by the lattice size of the surface is expressed as a percentage.

The lattice dimension is a distance between lattice points in a two-dimensional crystal lattice of one crystal plane, and can be measured by analyzing a crystal structure by X-ray diffraction, electron beam diffraction, or the like. In general, as the lattice matching ratio decreases, the first oriented particles have higher lattice matching with the crystal plane A and can function as a good template.
In order to obtain a crystallographically-oriented ceramic with a higher degree of orientation, the lattice matching rate of the first oriented particles is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

  “Anisotropic shape” means that the dimension in the longitudinal direction is larger than the dimension in the width direction or the thickness direction. Specifically, shapes such as a plate shape, a column shape, a scale shape, and a needle shape are preferable examples. Moreover, the kind of crystal plane which comprises the said orientation plane is not specifically limited, According to the objective, it can select from various crystal planes.

  Moreover, as said 1st orientation particle | grains, it is preferable to use what has a shape which can be easily oriented in a fixed direction at the time of the below-mentioned shaping | molding. For this reason, the first oriented particles preferably have an average aspect ratio of 3 or more. When the average aspect ratio is less than 3, it is difficult to orient the first anisotropically shaped powder in one direction in the molding process described later. In order to obtain the crystallographically-oriented ceramic having a higher degree of orientation, the aspect ratio of the first oriented particles is more preferably 5 or more. The average aspect ratio is an average value of the maximum dimension / minimum dimension of the first oriented particles.

  In addition, as the average aspect ratio of the first oriented particles increases, it becomes easier to orient the first oriented particles in the molding step. However, if the average aspect ratio is excessive, the oriented particles may be destroyed in the mixing step. As a result, in the molding step, a molded body in which the oriented particles are oriented may not be obtained. Therefore, the average aspect ratio of the oriented particles is preferably 100 or less. More preferably, it is 50 or less, and more preferably 30 or less.

The first oriented particles are made of a perovskite type compound.
Specifically, as the first oriented particles, particles having the same composition as the target isotropic perovskite compound, such as the compound represented by the general formula (3), can be used.
The first oriented particles do not necessarily have the same composition as the target isotropic perovskite compound, such as the compound represented by the general formula (3). Any material that produces the desired isotropic perovskite type compound by sintering may be used. Therefore, the first oriented particles can be selected from a compound containing any one or more of the cationic elements contained in the isotropic perovskite compound to be produced, a solid solution, or the like.

Examples of the first oriented particles satisfying the above conditions include NaNbO ₃ (hereinafter referred to as “NN”), KNbO ₃ (hereinafter referred to as [KN]), which is a kind of isotropic perovskite compound. ), Or (K _1-y Na _y ) NbO ₃ (0 <y <1), or a predetermined amount of Li, Ta and / or Sb substituted and solid-dissolved in the following general formula: What consists of a compound represented by (4) can be used.
_{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 ··· (4)
(However, x, y, z and w are 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1, respectively)

  The compound represented by the general formula (4) naturally has good lattice matching with the isotropic perovskite compound represented by the general formula (3). Therefore, a first anisotropically shaped powder (hereinafter referred to as the first anisotropically-shaped powder (hereinafter referred to as “the first anisotropically-shaped powder”), which is represented by the general formula (4) and has the crystal plane A in the polycrystalline body and the plane having lattice matching with the crystal plane A. In particular, this is called “anisotropically shaped powder A”), which functions as a reactive template for producing the above-mentioned crystallographically-oriented ceramic. Further, the anisotropically shaped powder A is composed of a cation element substantially contained in the isotropic perovskite type compound represented by the general formula (3). Can be manufactured. Among these, plate-like particles made of the compound represented by the above general formula (4) having a pseudo cubic {100} plane as the orientation plane are suitable as the orientation particles. Further, plate-like particles made of NN or KN having a pseudo-cubic {100} plane as an orientation plane are particularly suitable.

  Further, as the first anisotropically shaped powder, for example, the crystal plane A in a polycrystal composed of a layered perovskite compound and a crystal plane having a small surface energy represented by the compound represented by the general formula (3) Those having lattice matching can be used. Since the layered perovskite type compound has a large crystal lattice anisotropy, the layered perovskite type compound is composed of a layered perovskite type compound and has an anisotropically shaped powder (hereinafter referred to as “anisotropically shaped powder B”). Can be synthesized relatively easily.

As a first example of a layered perovskite type compound suitable as a material for the anisotropically shaped powder B, for example, there is a bismuth layered perovskite type compound represented by the following general formula (1).
(Bi ₂ O ₂ ) ²⁺ (Bi _0.5 Me _m-1 Nb _m O _{3m + 1} ) ^2- (1)
(Where m is an integer of 2 or more, Me is one or more selected from Li, K and Na)

Since the compound represented by the general formula (1) has a surface energy of {001} plane smaller than the surface energy of other crystal planes, {001} is obtained by using the compound represented by the general formula (1). The anisotropically shaped powder B having a plane as an orientation plane can be easily synthesized. Here, the {001} plane is a plane parallel to the (Bi ₂ O ₂ ) ²⁺ layer of the bismuth layered perovskite compound represented by the general formula (1). Moreover, the {001} plane of the compound represented by the general formula (1) is extremely good with the pseudo cubic {100} plane of the isotropic perovskite compound represented by the general formula (3) described later. Lattice matching.

  Therefore, the anisotropically-shaped powder B comprising the compound represented by the general formula (1) and having the {001} plane as the orientation plane produces a crystallographically-oriented ceramic having the pseudo cubic {100} plane as the orientation plane. Therefore, it is suitable as a reactive template for the first anisotropically shaped powder. Further, when the compound represented by the general formula (1) is used, the above general formula (3) is used so that Bi is not substantially contained as the A site element by optimizing the composition of the fine powder described later. Crystal oriented ceramics having an isotropic perovskite type compound represented by the following formula as a main phase can be produced.

A second example of a layered perovskite type compound suitable as the material for the anisotropically shaped powder B is, for example, Sr ₂ Nb ₂ O ₇ . The surface energy of the {010} plane of Sr ₂ Nb ₂ O ₇ is smaller than the surface energy of other crystal planes, and the pseudo cubic {110 of the isotropic perovskite compound represented by the general formula (3). } There is very good lattice matching with the surface. Therefore, the first anisotropic shaped powder composed of Sr ₂ Nb ₂ O ₇ and having the {010} plane as the orientation plane is used as a reactive template for producing a crystal-oriented ceramic having the {110} plane as the orientation plane. Is preferred.

As a third example of a layered perovskite compound suitable as a material for the anisotropically shaped powder B, for example, Na _1.5 Bi _2.5 Nb ₃ O ₁₂ , Na _2.5 Bi _2.5 Nb ₄ O ₁₅ , Bi ₃ TiNbO ₉ , Bi ₃ TiTaO ₉ , K _0.5 Bi _2.5 Nb ₂ O ₉ , CaBi ₂ Nb ₂ O ₉ , SrBi ₂ Nb ₂ O ₉ , BaBi ₂ Nb ₂ O ₉ , BaBi ₃ Ti ₂ NbO ₁₂ , CaBi ₂ Ta ₂ O ₉ , SrBi ₂ Ta ₂ O ₉ , BaBi ₂ Ta ₂ O ₉ , Na _0.5 Bi _2.5 Ta ₂ O ₉ , Bi ₇ Ti ₄ NbO ₂₁ , Bi ₅ Nb ₃ O _{15 and the} like. The {001} plane of these compounds has good lattice matching with the pseudocubic {100} plane of the isotropic perovskite compound represented by the general formula (3). Therefore, the first anisotropic shaped powder comprising these compounds and having the {001} plane as the orientation plane is suitable as a reactive template for producing a crystallographically-oriented ceramic having the pseudo cubic {100} plane as the orientation plane. It is.

As a fourth example of the layered perovskite type compound suitable as the material for the anisotropically shaped powder B, for example, there are Ca ₂ Nb ₂ O ₇ , Sr ₂ Ta ₂ O _{7 and the} like. The {010} plane of these compounds has good lattice matching with the pseudo cubic {110} plane of the isotropic perovskite compound represented by the general formula (3). Therefore, the first anisotropic shaped powder comprising these compounds and having the {010} plane as the orientation plane is suitable as a reactive template for producing a crystallographically-oriented ceramic having the pseudo cubic {110} plane as the orientation plane. It is.

Next, a method for producing the first anisotropically shaped powder will be described.
The first anisotropic shaped powder (that is, the anisotropic shaped powder B) composed of a layered perovskite compound having a predetermined composition, average particle size and / or aspect ratio is composed of an oxide, a carbonate, It can be easily manufactured by using nitrate or the like as a raw material (hereinafter referred to as “anisotropically shaped powder producing raw material”) and heating this anisotropically shaped powder producing raw material together with a liquid or a substance that becomes liquid by heating. .

  When the anisotropically shaped powder-forming raw material is heated in a liquid phase in which atoms are easily diffused, a surface with a small surface energy (for example, the {001} surface in the case of the compound represented by the general formula (1)) is preferential. It is possible to easily synthesize the anisotropically shaped powder B that has been developed. In this case, the average aspect ratio and the average particle diameter of the anisotropically shaped powder B can be controlled by appropriately selecting the synthesis conditions.

As a method for producing the anisotropic shaped powder B, for example, an appropriate flux (for example, NaCl, KCl, a mixture of NaCl and KCl, BaCl ₂ , KF, etc.) is added to the raw material for producing the anisotropic shaped powder at a predetermined temperature. Preferable examples include a heating method (flux method) and a method of heating an amorphous powder having the same composition as the anisotropically shaped powder B to be produced in an autoclave together with an alkaline aqueous solution (hydrothermal synthesis method). .

  On the other hand, since the compound represented by the general formula (4) has a very small anisotropy of the crystal lattice, the compound is represented by the general formula (4) and has a specific crystal plane as an orientation plane. It is difficult to directly synthesize the first anisotropic shaped powder (that is, the anisotropic shaped powder A). However, the anisotropically shaped powder A is manufactured by heating the above-mentioned anisotropically shaped powder B as a reactive template and a later-described reaction raw material B that satisfies a predetermined condition in a flux. Can do.

  In addition, when synthesizing the anisotropically shaped powder A using the anisotropically shaped powder B as the reactive template, if the reaction conditions are optimized, only the crystal structure changes, and the powder shape hardly changes. .

  In order to easily synthesize the anisotropically shaped powder A that can be easily oriented in one direction during molding, the anisotropically shaped powder B used for the synthesis also has a shape that can be easily oriented in one direction during molding. It is preferable to have.

  That is, even when the anisotropic shaped powder A is synthesized using the anisotropic shaped powder B as a reactive template, the average aspect ratio of the anisotropic shaped powder A is preferably at least 3 or more, more preferably 5 or more. More preferably, it is 10 or more. Moreover, in order to suppress the grinding | pulverization in a post process, it is preferable that an average aspect-ratio is 100 or less.

  The “reaction raw material B” refers to a material that reacts with the anisotropically shaped powder B to produce an anisotropically shaped powder A composed of at least the compound represented by the general formula (4). In this case, the reaction raw material B may generate only the compound represented by the general formula (4) by the reaction with the anisotropically shaped powder B. In the general formula (4), It may generate both the compound represented and the surplus component. Here, the “surplus component” refers to a substance other than the target compound represented by the general formula (4). Moreover, when an excess component produces | generates with the anisotropic shaped powder B and the reaction raw material B, it is preferable that an excess component consists of what is easy to remove thermally or chemically.

  As the form of the reaction raw material B, for example, oxide powder, composite oxide powder, carbonate, nitrate, oxalate salt, alkoxide, and the like can be used. The composition of the reaction raw material B can be determined by the composition of the compound represented by the general formula (4) to be produced and the composition of the anisotropically shaped powder B.

For example, an anisotropic shaped powder B made of Bi _2.5 Na _0.5 Nb ₂ O ₉ (hereinafter referred to as “BINN2”), which is one of the bismuth layered perovskite type compounds represented by the general formula (1), is used. Then, when synthesizing the anisotropic shaped powder A composed of NN which is a kind of the compound represented by the general formula (4), the reaction raw material B includes a compound containing Na (oxide, hydroxide, carbonic acid). Salt, nitrate, etc.) can be used. In this case, a Na-containing compound corresponding to 1.5 mol of Na atoms may be added as reaction raw material B to 1 mol of BINN2.

An appropriate flux (for example, NaCl, KCl, a mixture of NaCl and KCl, BaCl ₂ , KF, etc.) is 1% by weight to 500% by weight with respect to the anisotropic shaped powder B and the reaction raw material B having such a composition. In addition, when heated to the eutectic point / melting point, an excess component mainly composed of NN and Bi ₂ O ₃ is generated. Bi ₂ O ₃ has a low melting point and is weak against acids, and therefore, after removing the flux from the obtained reaction product by washing with hot water or the like, it is heated at a high temperature or acid washing is performed. } The anisotropically shaped powder A composed of NN with the plane as the orientation plane can be obtained.

Further, for example, using the anisotropically shaped powder B made of BINN2, (K _0.5 Na _0.5 ) NbO ₃ (hereinafter referred to as “KNN”) which is a kind of the compound represented by the general formula (4). In the case of synthesizing the anisotropically shaped powder A composed of), as the reaction raw material B, a compound containing Na (oxide, hydroxide, carbonate, nitrate, etc.) and a compound containing K (oxide, hydroxide) Compound, carbonate, nitrate, etc.) or a compound containing both Na and K may be used. In this case, a Na-containing compound corresponding to 0.5 mol of Na atom and a K-containing compound corresponding to 1 mol of K atom may be added as reaction raw material B to 1 mol of BINN2.

When an appropriate flux of 1 to 500% by weight is added to the anisotropic shaped powder B and the reaction raw material B having such a composition and heated to the eutectic point / melting point, KNN and Bi ₂ O ₃ are combined. Since an excess component as a main component is generated, if the flux and Bi ₂ O ₃ are removed from the obtained reaction product, an anisotropic shaped powder A composed of KNN having a {100} plane as an orientation plane can be obtained. .

  The same applies to the case where only the compound represented by the general formula (4) is produced by the reaction between the anisotropically shaped powder B and the reaction raw material B, and the anisotropically shaped powder B having a prescribed composition and the prescribed material. What is necessary is just to heat the reaction raw material B which has a composition in a suitable flux. Thereby, the compound represented with the said General formula (4) which has the target composition in a flux can be produced | generated. Further, if the flux is removed from the obtained reactant, an anisotropically shaped powder A having the above general formula (4) and having a specific crystal plane as an orientation plane can be obtained.

  Since the compound represented by the general formula (4) has a small crystal lattice anisotropy, it is difficult to directly synthesize the anisotropically shaped powder A. It is also difficult to directly synthesize the anisotropically shaped powder A having an arbitrary crystal plane as an orientation plane.

  On the other hand, the layered perovskite type compound has a large crystal lattice anisotropy, so that it is easy to directly synthesize anisotropically shaped powder. In addition, the orientation plane of the anisotropically shaped powder made of the layered perovskite compound often has lattice matching with a specific crystal plane of the compound represented by the general formula (4). Furthermore, the compound represented by the general formula (4) is thermodynamically stable as compared with the layered perovskite compound.

  Therefore, an anisotropically shaped powder B made of a layered perovskite compound and having an orientation plane having lattice matching with a specific crystal plane of the compound represented by the general formula (4) and the reaction raw material B are appropriately used. When the reaction is performed in a simple flux, the anisotropically shaped powder B can function as a reactive template. As a result, the anisotropically shaped powder A composed of the compound represented by the general formula (4) that inherits the orientation direction of the anisotropically shaped powder B can be easily synthesized.

  Further, when the composition of the anisotropically shaped powder B and the reaction raw material B is optimized, the A site element contained in the anisotropically shaped powder B (hereinafter referred to as “surplus A site element”) is surplus. An anisotropically shaped powder A made of a compound represented by the above general formula (4) that is discharged as a component and does not contain surplus A-site elements is produced.

In particular, when the anisotropically shaped powder B is composed of a bismuth layered perovskite compound represented by the general formula (1), Bi is discharged as a surplus A site element, and a surplus component mainly composed of Bi ₂ O ₃ is present. Generate. Therefore, if this surplus component is removed thermally or chemically, it is substantially anisotropic and is composed of a compound represented by the above general formula (4) and having a specific crystal plane as an orientation plane. Shape powder A can be obtained.

Next, the pulverization step in the first invention will be described.
In the pulverization step, as described above, the first anisotropic shaped powder is pulverized by a jet mill. In this pulverization step, the shape of the first oriented particles can be made into a plate shape or the like, and the average particle size, aspect ratio, etc. of the oriented particles can be controlled.

In the pulverization step, the first anisotropic shaped powder is formed into a plate shape, and the first anisotropic shaped powder is pulverized so that the average particle diameter of the first anisotropic shaped powder is 1 μm to 13 μm. (Claim 2).
In this case, as described above, the piezoelectric characteristics and temperature characteristics of the crystallographically-oriented ceramic can be easily controlled, and the oriented surface of the first anisotropically shaped powder is oriented in the compact in the subsequent molding process. It becomes easy.

  When the average particle diameter (average value in the longitudinal direction) of the first oriented particles is less than 1 μm, it is difficult to orient the first oriented particles in a certain direction by, for example, shear stress in the molding step. become. In addition, since the gain of the interface energy is small, when used as a reactive template for producing the above-mentioned crystallographically-oriented ceramic, there is a possibility that epitaxial growth on template particles (first oriented particles) is difficult to occur. On the other hand, when it exceeds 13 μm, the sinterability is lowered, and there is a possibility that a crystal-oriented ceramic having a high sintered body density cannot be obtained after the firing step. More preferably, the average particle diameter of the first oriented particles is preferably 2 μm to 10 μm, and more preferably 2 μm to 8 μm.

In the first oriented particles, the oriented surface is preferably the largest surface that occupies the widest area in the first oriented particles.
In this case, the first oriented particles can be used as a better reactive template for producing the crystal oriented ceramics.

Moreover, in the said 2nd invention, the said 1st anisotropic shaped powder is prepared by performing the said preparatory process.
That is, in the preparation step, the second anisotropic shaped powder is made of a layered perovskite type compound, and the crystal plane having the smallest surface energy is made of the second oriented particles having lattice matching with the oriented surface of the first oriented particles. And preparing a reaction raw material for producing the first anisotropic shaped powder by reacting with the second anisotropic shaped powder after the grinding process and grinding the second anisotropic shaped powder. Then, the reaction raw material and the second anisotropic shaped powder are heated in a flux to perform a heat treatment process for producing the first anisotropic shaped powder.

The second anisotropically shaped powder is one of the raw materials of the first anisotropically shaped powder and is made of a layered perovskite type compound, and the crystal plane having the smallest surface energy is the orientation plane of the first oriented particles. It consists of second oriented particles having lattice matching.
As such second anisotropic shaped powder, for example, the same powder as the anisotropic shaped powder B can be used.
Preferably, the second anisotropically shaped powder has a general formula (1): (Bi ₂ O ₂ ) ²⁺ (Bi _0.5 Me _m-1.5 Nb _m O _{3m + 1} ) ²⁻ (where m is 2 or more) An integer, Me is preferably composed of a bismuth layered perovskite type compound represented by one or more selected from Na, K, and Li (Claim 5).
In this case, by heating the second anisotropic shaped powder together with the reaction raw material in a flux, the first anisotropic shaped powder made of, for example, the compound represented by the general formula (4) can be easily produced. can do. Further, from the viewpoint of ease of synthesis, m in the general formula (1) is more preferably an integer of 10 or less.

In addition, it is preferable that the second oriented particles have a lattice matching with the oriented surface of the first oriented particles, the largest surface having the largest area on the surface.
In this case, the second oriented particles can be a better reactive template for producing the first oriented particles.

In the preparation step, the second anisotropic shaped powder is pulverized by a jet mill (pulverization process).
In the pulverization process, while maintaining the plate shape of the second anisotropic shaped powder, the second anisotropic shaped powder is adjusted so that the average particle diameter of the second anisotropic shaped powder is 1 μm to 13 μm. It is preferable to grind (Claim 6).
In this case, the first anisotropic shaped powder having a plate shape and an average particle diameter of 1 μm to 13 μm can be easily obtained. Therefore, as described above, the piezoelectric characteristics and temperature characteristics of the crystal-oriented ceramics can be easily controlled, and the oriented surface of the first anisotropically shaped powder can be easily oriented in the compact in the subsequent molding process. become.

When the average particle size of the second anisotropic shaped powder is less than 1 μm, the average particle size of the first anisotropic shaped powder obtained after the heat treatment step tends to be less than 1 μm. As a result, in the molding step, it becomes difficult to orient the first oriented particles in a certain direction due to, for example, shear stress. In addition, since the gain of the interface energy is small, when used as a reactive template for producing the above-mentioned crystallographically-oriented ceramic, there is a possibility that epitaxial growth on template particles (first oriented particles) is difficult to occur. On the other hand, when it exceeds 13 μm, the average particle diameter of the first anisotropic shaped powder obtained after the heat treatment step tends to exceed 13 μm. As a result, the sinterability is lowered, and there is a possibility that a crystal-oriented ceramic having a high sintered body density cannot be obtained after the firing step. More preferably, the average particle diameter of the second anisotropic shaped powder is 2 μm to 10 μm, and more preferably 2 μm to 8 μm.
Further, as the reaction raw material that reacts with the second anisotropic shaped powder, the same material as the reaction raw material B can be used.

  The reaction raw material reacts with the second anisotropically shaped powder to produce the first anisotropically shaped powder made of, for example, a perovskite type compound represented by the general formula (4). In this case, the reaction raw material may generate only the isotropic perovskite type compound represented by the general formula (4), for example, by reaction with the second anisotropically shaped powder, or the above You may produce | generate both an isotropic perovskite type compound and a surplus component. Moreover, when a surplus component produces | generates by reaction with the said anisotropically shaped powder and the said reaction raw material, it is preferable that a surplus component is a thing which is easy to remove thermally or chemically.

The composition of the reaction raw material can be determined according to the composition of the second anisotropic shaped powder and the composition of the first anisotropic shaped powder to be produced. Moreover, as said reaction raw material, oxide powder, complex oxide powder, hydroxide powder, salt, such as carbonate, lead nitrate, a main acid salt, or an alkoxide can be used, for example.
Specifically, as the reaction raw material, for example, the same material as the reaction raw material B can be used.

In the heat treatment process, the first anisotropic shaped powder and the reaction raw material are heated in a flux.
As the flux, for example, NaCl, KCl, a mixture of NaCl and KCl, BaCl ₂ , KF, or the like can be used.

In the first invention and the second invention, the first oriented particles are composed of an isotropic perovskite compound represented by the general formula (2) ABO ₃ , and the A in the general formula (2) The site element is mainly composed of one or more selected from K, Na and Li, and the B site element in the general formula (2) is mainly composed of one or more selected from Nb, Sb and Ta. Preferred (claim 7).
In this case, by using the first oriented particles, an isotropic perovskite-type potassium sodium niobate-based crystal-oriented ceramic exhibiting relatively high piezoelectric characteristics among non-lead-based particles can be produced.

Further, the first alignment particles, formula _{(4): {Li x (} K 1-y Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 ( where, 0 ≦ x ≦ 1 , 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1).
In this case, the above-mentioned crystallographically-oriented ceramic with a high degree of orientation can be produced.
That is, as described above, the compound represented by the general formula (4) has good lattice matching with the compound represented by the general formula (3). Therefore, the anisotropically shaped powder comprising the oriented particles represented by the general formula (4) and having a specific crystal plane as the oriented plane is a good reactive template for producing the crystal oriented ceramics. Can function.

The orientation plane of the first oriented particles is preferably a pseudo-cubic {100} plane.
In this case, the temperature dependence of the displacement generated under a large electric field can be improved in a tetragonal region where the orientation axis and the polarization axis coincide.

  In the first and second inventions, the mixing step has an average particle size of 1/3 or less of the first anisotropic shaped powder and is sintered together with the first anisotropic shaped powder. To prepare a fine powder for producing the isotropic perovskite compound, and the fine powder and the first anisotropically shaped powder are mixed to prepare a raw material mixture.

The fine powder generates the isotropic perovskite compound by sintering together with the first anisotropic shaped powder, and has an average particle size of 1/3 or less of the first anisotropic shaped powder. .
When the average particle size of the fine powder exceeds 1/3 of the average particle size of the first anisotropic shaped powder, in the molding step, the orientation planes of the first anisotropic shaped powder are in substantially the same direction. It may be difficult to form the raw material mixture so as to be oriented in the direction. More preferably, it is 1/4 or less, and further preferably 1/5 or less.

When the first anisotropically shaped powder is a powder having the same composition as the target isotropic perovskite compound, such as the compound represented by the general formula (3), the fine powder However, the same composition as the first anisotropically shaped powder, that is, the same composition as the target isotropic perovskite compound can be used.
In addition, the fine powder reacts with the first anisotropically shaped powder by sintering together with the first anisotropically shaped powder, for example, as a compound represented by the general formula (3). Those that produce an isotropic perovskite type compound can be used.
In this case, the fine powder may generate only the target isotropic perovskite type compound by reaction with the first anisotropically shaped powder, or the target isotropic perovskite type compound and the surplus. It may generate both of the components. Moreover, when a surplus component produces | generates by reaction with the said 1st anisotropic shaped powder and the said 1st fine powder, it is preferable that this surplus component is easy to remove thermally or chemically.

Preferably, the first anisotropic shaped powder and the fine powder have different compositions, and the isotropic perovskite type is caused by causing a chemical reaction between the anisotropic shaped powder and the fine powder in the firing step. A compound is preferably produced (claim 9).
In this case, it is possible to easily synthesize the first anisotropically shaped powder as a raw material for producing the crystallographically-oriented ceramic.

  The composition of the fine powder can be determined according to the composition of the first anisotropically shaped powder and the composition of the isotropic perovskite compound to be produced, such as the compound represented by the general formula (3). Further, as the fine powder, for example, oxide powder, composite oxide powder, hydroxide powder, carbonate, nitrate, salt of main acid salt, alkoxide, or the like can be used.

  Specifically, for example, crystal orientation composed of an isotropic perovskite compound represented by the above general formula (3) using an anisotropic shaped powder A having a KNN composition or an NN composition as the first anisotropic shaped powder. In the case of producing ceramics, a mixture of compounds containing at least one element of Li, K, Na, Nb, Ta and Sb is used as the fine powder, and the anisotropically shaped powder A and the fine powder These may be blended at a stoichiometric ratio such that an isotropic perovskite compound represented by the above general formula (3) having the desired composition is generated.

  Further, for example, an isotropic perovskite compound represented by the general formula (3) is obtained by using the anisotropic shaped powder B having the composition represented by the general formula (1) as the first anisotropic shaped powder. In the case of producing a crystallographically-oriented ceramic comprising, a mixture of compounds containing at least one element of Li, K, Na, Nb, Ta and Sb is used as the fine powder, and the anisotropic shaped powder B and What is necessary is just to mix | blend these by the stoichiometric ratio which the compound represented with the said general formula which has the target composition from the said fine powder produces | generates. The same applies to the production of crystallographically oriented ceramics having other compositions.

  Further, in the mixing step, the first anisotropically shaped powder and the fine powder blended at a predetermined ratio are expressed by, for example, the general formula (3) obtained by reaction of these substances. Adding amorphous fine powder (hereinafter referred to as “compound fine powder”) composed of a compound having the same composition as the isotropic perovskite type compound, and / or a sintering aid such as CuO. You can also. When the compound fine powder and the sintering aid are added, there is an advantage that densification of the sintered body is further facilitated.

  In addition, when blending the compound fine powder, if the blending ratio of the compound fine powder is excessive, the blending ratio of the anisotropically shaped powder occupying the whole raw material is inevitably small, and the degree of orientation of a specific crystal plane is May decrease. Therefore, it is preferable to select an optimum blending ratio of the compound fine powder according to a required sintered body density and orientation degree.

When producing the isotropic perovskite type compound represented by the general formula (3), the blending ratio of the first anisotropic shaped powder is one or more components in the first anisotropic shaped powder. It is preferable that the ratio at which the A site of the compound of the above general formula (3) represented by ABO ₃ is occupied by the element is 0.01 to 70 at%, more preferably 0.1 to 70 at%. 50 at% is good. More preferably, 1 to 10 at% is good. Here, “at%” indicates the percentage of the number of atoms in 100 minutes.

  Further, the mixing of the first anisotropically shaped powder, the fine powder, and the compound fine powder blended as necessary and the sintering aid may be carried out by a dry method, or an appropriate dispersion of water, alcohol or the like. It may be carried out wet by adding a medium. Further, at this time, a binder and / or a plasticizer may be added as necessary.

Next, the molding process will be described.
The forming step is a step of forming the raw material mixture to form a molded body so that the oriented surfaces of the first anisotropic shaped powder are oriented in substantially the same direction.
In this case, the first anisotropic shaped powder may be molded so as to be plane-oriented, or the first anisotropic shaped powder may be shaped so as to be axially oriented.

  Any molding method may be used as long as the first anisotropic shaped powder can be oriented. Specific examples of the molding method for orienting the first anisotropically shaped powder include a doctor blade method, a press molding method, and a rolling method. Specific examples of the molding method for axially orienting the first anisotropic shaped powder include an extrusion molding method and a centrifugal molding method.

Further, in order to increase the thickness of the molded body in which the first anisotropically shaped powder is surface-oriented (hereinafter referred to as “surface-oriented molded body”) or to increase the degree of orientation, Furthermore, processing such as laminating and pressing, pressing and rolling (hereinafter referred to as “plane orientation processing”) can be performed.
In this case, any one type of surface alignment treatment can be performed on the above-mentioned surface alignment molded body, but two or more types of surface alignment processing can also be performed. In addition, one type of surface alignment treatment can be repeatedly performed on the above-described surface alignment molded body, and two or more types of alignment processing can be repeatedly performed a plurality of times.

Next, the firing process will be described.
The firing step is a step of heating the molded body to sinter the first anisotropic shaped powder and the fine powder.
In the firing step, the sintered body is heated by heating the shaped body, and a crystal-oriented ceramic composed of a polycrystalline body having an isotropic perovskite type compound as a main phase is produced. At this time, the first anisotropically shaped powder and the fine powder can be reacted to produce the isotropic perovskite compound such as the compound represented by the general formula (3).
Moreover, in the said baking process, an excess component is also produced | generated simultaneously depending on the composition of the said anisotropically shaped powder and / or fine powder.

  The heating temperature in the firing step is such that the reaction and / or sintering proceeds efficiently and a reaction product having the desired composition is produced, the anisotropic shaped powder to be used, the reaction raw material, and the crystal to be produced. The optimum temperature can be selected according to the composition of the oriented ceramics.

  For example, in the case of producing a crystallographically-oriented ceramic composed of the compound represented by the general formula (3) using the anisotropically shaped powder A having the first anisotropically shaped powder KNN composition, The heating temperature can be 900 ° C. or higher and 1300 ° C. or lower. Further optimum heating temperature in this temperature range can be determined according to the composition of the compound represented by the general formula (3) which is the target substance. Furthermore, as the heating time, an optimal time can be selected according to the heating temperature so that a desired sintered body density can be obtained.

  Moreover, when a surplus component produces | generates by reaction with the said 1st anisotropic shaped powder and the said fine powder, a surplus component can be made to remain as a subphase in a sintered compact. Further, excess components can be removed from the sintered body. In the case of removing the surplus components, as described above, there are, for example, a method of removing thermally, a method of removing chemically, and the like.

  As a method for thermally removing, for example, a sintered body (hereinafter referred to as “intermediate sintered body”) in which a compound represented by the general formula (3) and an excess component are generated is heated at a predetermined temperature. However, there is a method of volatilizing excess components. Specifically, a method in which the intermediate sintered body is heated for a long time at a temperature at which excess components volatilize is given under reduced pressure or in oxygen.

  The heating temperature for removing the surplus component thermally is such that the volatilization of the surplus component proceeds efficiently and the production of by-products is suppressed, and the compound represented by the above general formula (3) and / or Alternatively, an optimum temperature can be selected according to the composition of the surplus component. For example, when the surplus component is a bismuth oxide single phase, the heating temperature is preferably 800 ° C. or higher and 1300 ° C. or lower, more preferably 1000 ° C. or higher and 1200 ° C. or lower.

  Moreover, as a method of chemically removing the surplus component, for example, there is a method of immersing the intermediate sintered body in a processing solution having a property of eroding only the surplus component and extracting the surplus component. At this time, as the treatment liquid to be used, an optimum one can be selected according to the composition of the compound represented by the general formula (3) and / or the surplus component. For example, when the surplus component is a bismuth oxide single phase, an acid such as nitric acid or hydrochloric acid can be used as the treatment liquid. In particular, nitric acid is suitable as a treatment liquid for chemically extracting surplus components mainly composed of bismuth oxide.

  The reaction between the first anisotropically shaped powder and the fine powder and the removal of excess components may be performed simultaneously, sequentially, or individually. For example, the compact is directly heated to a temperature at which both the reaction between the first anisotropic shaped powder and the fine powder and the volatilization of the surplus component proceed efficiently under reduced pressure or under vacuum, and the surplus component is removed simultaneously with the reaction. It can be performed. The additive element is replaced with the compound represented by the general formula (3), which is the target substance, in the reaction between the first anisotropically shaped powder and the fine powder, or crystal grains as described above. It is arranged inside or / and in the grain boundary.

  Further, for example, in the atmosphere or oxygen, after heating the compact at a temperature at which the reaction between the first anisotropic shaped powder and the fine powder proceeds efficiently, the intermediate sintered body is generated, It is also possible to remove the surplus component by heating the sintered body at a temperature at which the volatilization of the surplus component proceeds efficiently under reduced pressure or under vacuum. In addition, after the intermediate sintered body is generated, the intermediate sintered body is subsequently heated in the atmosphere or oxygen for a long time at a temperature at which the volatilization of the surplus components efficiently proceeds to remove the surplus components. You can also.

  In addition, for example, after the intermediate sintered body is generated and the intermediate sintered body is cooled to room temperature, the intermediate sintered body is immersed in a treatment liquid to remove excess components chemically. Alternatively, after the intermediate sintered body is generated and cooled to room temperature, the intermediate sintered body is again heated to a predetermined temperature in a predetermined atmosphere to remove excess components thermally.

  When the molded body obtained in the molding step includes a binder, heat treatment mainly for degreasing can be performed before the firing step. In this case, the degreasing temperature can be set to a temperature that is at least sufficient to thermally decompose the binder. However, in the case where a material that easily volatilizes (for example, Na compound) is contained in the raw material mixture, the degreasing is preferably performed at 500 ° C. or less.

  Moreover, when the molded body is degreased, the degree of orientation of the first anisotropically shaped powder in the molded body may decrease, or volume expansion may occur in the molded body. In such a case, it is preferable to perform a hydrostatic pressure (CIP) treatment on the molded body after degreasing and before the heat treatment step. In this case, it is possible to suppress a decrease in the degree of orientation accompanying degreasing or a decrease in the density of the sintered body due to the volume expansion of the molded body.

  Further, when the surplus component is generated by the reaction between the first anisotropic shaped powder and the reaction raw material, when removing the surplus component, the intermediate sintered body from which the surplus component has been removed is further subjected to a hydrostatic pressure treatment. Can be applied and refired. Moreover, in order to further raise a sintered compact density and orientation degree, a hot press can be further performed with respect to the sintered compact after the said heat processing process. Furthermore, a method of adding the above compound fine powder, a method such as CIP treatment, and hot pressing may be used in combination.

  In the production method of the present invention, as described above, the anisotropic powder B made of a layered perovskite compound that is easy to synthesize is used as a reactive template, and the compound made of the compound represented by the general formula (4) is used. The anisotropically shaped powder A can be synthesized, and then the anisotropically shaped powder A can be used as a reactive template to produce the crystal oriented ceramic. In this case, even if it is a compound represented by the said General formula (3) with small anisotropy of a crystal lattice, the said crystal orientation ceramics in which arbitrary crystal planes orientated can be manufactured easily and cheaply. .

  And if the composition of the said anisotropically shaped powder B and the reaction raw material B is optimized, even if it is the anisotropically shaped powder A which does not contain a surplus A site element, it is compoundable. Therefore, the composition control of the A site element becomes easy, and a crystallographically-oriented ceramic having the main phase of the compound represented by the general formula (3) having a composition that cannot be obtained by a conventional method can be produced.

  Moreover, as said 1st anisotropically shaped powder, the anisotropically shaped powder B which consists of a layered perovskite type compound can be used. In this case, in the firing step, the compound represented by the general formula (3) can be synthesized simultaneously with the sintering. Further, by optimizing the composition of the anisotropically shaped powder B to be oriented in the molded body and the reaction raw material to be reacted therewith, the target compound represented by the general formula (3) is synthesized and The surplus A site element can be discharged from the square powder B as a surplus component.

  In addition, when the anisotropically shaped powder B that generates a surplus component that can be easily removed thermally or chemically is used as the first anisotropically shaped powder, it does not substantially contain an excess A site element, and A crystallographically-oriented ceramic comprising a compound represented by the general formula (3) and having a specific crystal plane oriented can be obtained.

In the present invention, the above-mentioned crystallographically-oriented ceramic is made of a polycrystal having an isotropic perovskite compound as a main phase. As the isotropic perovskite type compound constituting the polycrystal, for example, potassium sodium niobate (K _{1 -y} Na _y ) NbO ₃ is used as a basic composition, and a part of the A-site element (K, Na) is a predetermined amount. Some are substituted with Li and / or part of the B site element (Nb) is substituted with a predetermined amount of Ta and / or Sb.

Preferably, the polycrystalline body, the general formula (3): {Lix (K 1-y Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 ( where, 0 ≦ x ≦ 0. (2) 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0) is preferably used as the main phase (claim 11). ).
In this case, the piezoelectric characteristics, dielectric characteristics, and temperature characteristics of the crystal oriented ceramics can be further improved.
In the general formula (3), “x + z + w> 0” indicates that at least one of Li, Ta, and Sb may be included as a substitution element.

In the general formula (3), “y” represents the ratio of K and Na contained in the isotropic perovskite compound. The isotropic perovskite compound only needs to contain at least one of K or Na as the A site element.
The range of y in the general formula (3) is more preferably 0 <y ≦ 1.
In this case, Na is an essential component in the compound represented by the general formula (1). Therefore, in this case, the piezoelectric g ₃₁ constant of the crystal-oriented ceramic can be further improved.
The range of y in the general formula (3) can be 0 ≦ y <1.
In this case, K is an essential component in the compound represented by the general formula (3). Therefore, in this case, the piezoelectric characteristics such as the piezoelectric d ₃₁ constant of the crystal-oriented ceramic can be further improved. Further, in this case, since the sintering at a lower temperature becomes possible as the K addition amount increases, the above-mentioned crystallographically-oriented ceramic can be produced with energy saving and low cost.
In the general formula (3), y is more preferably 0.05 ≦ y ≦ 0.75, and further preferably 0.20 ≦ y ≦ 0.70. In these cases, the piezoelectric d ₃₁ constant and the total number of electrical solutions Kp of the crystal oriented ceramics can be further improved. Even more preferably, 0.20 ≦ y <0.70 is satisfied, 0.35 ≦ y ≦ 0.65 is further preferable, and 0.35 ≦ y <0.65 is more preferable. Most preferably, 0.42 ≦ y ≦ 0.60.

“X” represents a substitution amount of Li for substituting K and / or Na which are A site elements. Replacing a part of K and / or Na with Li provides the effect of improving the piezoelectric characteristics, increasing the Curie temperature, and / or promoting densification.
The range of x in the general formula (3) is preferably 0 <x ≦ 0.2.
In this case, in the compound represented by the general formula (3), Li is an essential component. Therefore, the crystallographically-oriented ceramic can be easily fired at the time of production, and has piezoelectric characteristics. This further improves the Curie temperature (Tc). This is because by making Li an essential component within the range of x described above, the firing temperature is lowered, and Li serves as a firing aid, enabling firing with fewer voids.
If the value of x exceeds 0.2, the piezoelectric characteristics (piezoelectric d ₃₁ constant, electromechanical coupling coefficient kp, piezoelectric g ₃₁ constant, etc.) may be reduced.

In addition, the value x in the general formula (3) can be set to x = 0.
In this case, the general formula (3) is represented by _{(K 1-y Na y)} (Nb 1-zw Ta z Sb w) O 3. In this case, when producing the crystal oriented ceramic, since the raw material does not include a compound containing the lightest Li, such as LiCO ₃ , the raw materials are mixed and the crystal oriented ceramic is mixed. The variation in characteristics due to segregation of the raw material powder can be reduced. In this case, a high relative dielectric constant and a relatively large piezoelectric g constant can be realized.
In the general formula (3), the value of x is more preferably 0 ≦ x ≦ 0.15, and further preferably 0 ≦ x ≦ 0.10.

“Z” represents the amount of Ta substituted for Nb which is a B-site element. If a part of Nb is replaced with Ta, an effect of improving the piezoelectric characteristics and the like can be obtained. In the general formula (3), if the value of z exceeds 0.4, the Curie temperature is lowered, which may make it difficult to use it as a piezoelectric material for home appliances and automobiles.
The range of z in the general formula (3) is preferably 0 <z ≦ 0.4.
In this case, Ta is an essential component in the compound represented by the general formula (1). Therefore, in this case, the sintering temperature is lowered, and Ta serves as a sintering aid, so that the number of pores in the crystal-oriented ceramic can be reduced.

The value of z in the general formula (3) can be set to z = 0.
In this case, the general formula (3) is represented by {Li _x (K _1−y Na _y ) _1−x } (Nb _1−w Sb _w ) O ₃ . In this case, the compound represented by the general formula (3) does not contain Ta. Therefore, in this case, the compound represented by the general formula (3) can exhibit excellent piezoelectric characteristics without using an expensive Ta component at the time of production.
In the general formula (3), the value of z is more preferably 0 ≦ z ≦ 0.35, and further preferably 0 ≦ z ≦ 0.30.

Further, “w” represents the substitution amount of Sb that substitutes Nb, which is a B site element. If a part of Nb is replaced with Sb, an effect of improving the piezoelectric characteristics and the like can be obtained. If the value of w exceeds 0.2, the piezoelectric characteristics and / or the Curie temperature are lowered, which is not preferable.
Moreover, it is preferable that the value of w in the said General formula (3) is 0 <w <= 0.2.
In this case, Sb is an essential component in the compound represented by the general formula (3). Therefore, in this case, the sintering temperature can be lowered, the sinterability can be improved, and the stability of the dielectric loss tan δ can be improved.

In addition, the value of w in the general formula (3) can be set to w = 0.
In this case, the general formula (3) is represented by {Li _x (K _1−y Na _y ) _1−x } (Nb _1−z Ta _z ) O ₃ . In this case, the compound represented by the general formula (1) does not contain Sb and can exhibit a relatively high Curie temperature.
In the general formula (3), the value of w is more preferably 0 ≦ w ≦ 0.15, and further preferably 0 ≦ w ≦ 0.10.

  The crystal-oriented ceramic is preferably composed only of the isotropic perovskite type compound represented by the general formula (3), but the isotropic perovskite type crystal structure can be maintained, and the sintering characteristics, Other elements or other phases may be included as long as they do not adversely affect various characteristics such as piezoelectric characteristics.

Further, the polycrystal is composed of a metal element, a semimetal element, or a transition metal element belonging to Groups 2 to 15 in the periodic table with respect to 1 mol of the isotropic perovskite compound represented by the general formula (3). It is preferable that 0.0001 to 0.15 mol of one or more additive elements selected from the group consisting of noble metal elements and alkaline earth metal elements is contained.
In this case, piezoelectric characteristics such as the piezoelectric d ₃₁ constant, the electromechanical coupling coefficient Kp, and the piezoelectric g ₃₁ constant of the crystallographically-oriented ceramic, the dielectric constant, the dielectric loss, and the like can be improved. In the crystal oriented ceramics, the additive element may be substituted for the compound represented by the general formula (3), but is added externally and represented by the general formula (3). It can also be present in the grain or grain boundary of the compound. The additive element may be contained as a single additive element, or may be contained as an oxide or a compound containing the additive element.
When the content of the additive element is less than 0.0001 mol, there is a possibility that the effect of improving the piezoelectric characteristics by the additive element cannot be sufficiently obtained. On the other hand, if it exceeds 0.15 mol, the piezoelectric properties and dielectric properties of the above-mentioned crystallographically-oriented ceramic may be deteriorated.

  Specific examples of the additive element include Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Hf, W, There are Re, Pd, Ag, Ru, Rh, Pt, Au, Ir, Os, B, Al, Ga, In, Si, Ge, Sn, and Bi.

Further, the additive element, the general formula (3): {Lix (K 1-y Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 ( where, 0 ≦ x ≦ 0.2 , 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0), one kind selected from Li, K, Na, Nb, Ta, and Sb It is preferable that substitution is added at a ratio of 0.01 to 15 at% with respect to the above elements.
In this case, the piezoelectric properties such as the piezoelectric d ₃₁ constant and the electromechanical coupling coefficient Kp of the crystal-oriented ceramic and the dielectric properties such as the relative dielectric constant ε _33T / ε ₀ can be further improved.
When the additive element is less than 0.01 at%, there is a risk that the effect of improving the piezoelectric characteristics and dielectric characteristics of the crystal-oriented ceramics cannot be sufficiently obtained. On the other hand, if it exceeds 15 at%, the piezoelectric properties and dielectric properties of the above-mentioned crystallographically-oriented ceramic may be deteriorated. More preferably, 0.01 to 5 at% is good, still more preferably 0.01 to 2 at%, and still more preferably 0.05 to 2 at%.
Here, “at%” means the ratio of the number of substituted atoms to the number of atoms of Li, K, Na, Nb, Ta, and Sb in the compound represented by the general formula (3) as 100 minutes. It is shown in rate.

Example 1
Next, examples of the present invention will be described.
This example is an example of producing a crystallographically-oriented ceramic made of a polycrystal having an isotropic perovskite type compound as a main phase, in which specific crystal planes of crystal grains constituting the polycrystal are oriented.

In the method for producing a crystallographically-oriented ceramic of this example, a preparation process, a mixing process, a forming process, and a firing process are performed.
In the preparation step, a first anisotropic shaped powder is prepared which is made of a perovskite type compound and includes first oriented particles having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented.
In the mixing step, a fine particle having an average particle size of 1/3 or less of the first anisotropic shaped powder after the pulverizing step and producing an isotropic perovskite type compound by sintering together with the first anisotropic shaped powder. A powder is prepared, and the fine powder and the first anisotropic shaped powder are mixed to prepare a raw material mixture.
In the forming step, the raw material mixture is formed so that the oriented surfaces of the first anisotropic shaped powder are oriented in substantially the same direction to produce a shaped body.
In the heat treatment step, the compact is heated to sinter the first anisotropic shaped powder and the fine powder.

In the preparation process of this example, the first anisotropic shaped powder is prepared by performing the following pulverization process and heat treatment process.
In the pulverization process, a second anisotropic shaped powder comprising a layered perovskite-type compound and having a crystal plane with the smallest surface energy and second oriented particles having lattice matching with the oriented surface of the first oriented particles is prepared. The second anisotropic shaped powder is pulverized.
In the heat treatment process, a reaction raw material that generates the first anisotropic shaped powder by reacting with the second anisotropic shaped powder after the pulverization process is prepared, and the reaction raw material, the second anisotropic shaped powder, Is heated in a flux to produce the first anisotropically shaped powder.

(1) Production of first anisotropic shaped powder First, a plate-like powder made of NaNbO ₃ is synthesized as a first anisotropic shaped powder as follows.
That is, first, Bi ₂ O ₃ powder, Na ₂ CO ₃ powder and Nb ₂ O ₅ powder were weighed at a stoichiometric ratio such that the composition of Bi _2.5 Na _3.5 Nb ₅ O ₁₈ was obtained, and these were wet mixed. . Next, 50 wt% NaCl was added as a flux to this raw material, and dry mixed for 1 hour.
Next, the obtained mixture was put into a platinum crucible and heated under the conditions of 850 ° C. × 1 h to completely dissolve the flux, and further heated under the conditions of 1100 ° C. × 2 h to obtain Bi _2.5 Na _3.5 Nb. ₅ O ₁₈ was synthesized. The temperature rising rate was 200 ° C./hr, and the temperature lowering was furnace cooling. After cooling, the flux was removed from the reaction product by hot water washing to obtain Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder (second anisotropic shaped powder). The obtained Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder was a plate-like powder having the {001} plane as the orientation plane (maximum plane).

Next, Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder was pulverized by a jet mill.
Scanning electron micrographs of Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder before and after grinding are shown in FIGS. FIG. 1 is a photograph before grinding, and FIG. 2 is a photograph after grinding. The Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder after pulverization had an average particle size of about 4 μm and an aspect ratio of about 3 to 6.

Next, to this Bi _2.5 Na _3.5 Nb ₅ O ₁₈ plate-like powder, an amount of Na ₂ CO ₃ powder (reaction raw material) necessary for the synthesis of NaNbO ₃ is added and mixed, and NaCl is used as a flux in a platinum crucible. , Heat treatment was performed at 950 ° C. for 8 hours.
Since the obtained reaction product contains Bi ₂ O ₃ in addition to NaNbO ₃ powder, after removing the flux from the reaction product, it was put in HNO ₃ (1N) and produced as an extra component. Bi ₂ O ₃ was dissolved. Further, this solution was filtered to separate NaNbO ₃ powder and washed with ion exchange water at 80 ° C. There was thus obtained powder comprising NaNbO ₃ as the first anisotropically-shaped powder (NaNbO ₃ powder).
The obtained NaNbO ₃ powder was a plate-like powder having a pseudo cubic {100} plane as the maximum plane (orientation plane), an average particle diameter of 4 μm, and an aspect ratio of about 3 to 6.

(2) Preparation of crystal-oriented ceramics having a composition in which 0.0005 mol of Mn is externally added to 1 mol of {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ Purity 99.99% The above Na ₂ CO ₃ powder, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, Sb ₂ O ₅ powder and MnO ₂ powder were _added {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ + Mn 0.0005 mol stoichiometric composition 1 mol of NaNbO ₃ is weighed so as to be a composition obtained by subtracting 0.05 mol of NaNbO ₃ and using ZrO ₂ balls as an organic solvent. Wet mixing for hours was performed. Thereafter, calcination was performed at 750 ° C. for 5 hours, and further, wet pulverization was performed with a ZrO ₂ ball for 20 hours using an organic solvent as a medium to obtain a calcined powder (fine powder) having an average particle diameter of about 0.5 μm.

The calcined product powder and a NaNbO ₃ of the plate-like _{{Li 0.065 (K 0.45 Na 0.55} ) 0.935} (Nb 0.83 Ta 0.09 Sb 0.08) O 3 + were weighed so as to the composition of Mn0.0005Mol, the organic solvent A slurry was obtained by using a ZrO ₂ ball as a medium for 20 hours of wet mixing. Thereafter, a binder (PVB) and a plasticizer (dibutyl phthalate) are added to the slurry with 1 mol of {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } {Nb _0.83 Ta _0.09 Sb _0.08 } O ₃ + Mn0 synthesized from the starting materials. 10.35 g and 10.35 g were added to .0005 mol, respectively, and further mixed for 2 hours.

  Next, the mixed slurry was formed into a tape having a thickness of 100 μm using a doctor blade device. Further, a laminated sheet having a thickness of 1.5 mm was obtained by laminating, pressing and rolling the tape. Subsequently, the obtained plate-like molded body was degreased in the atmosphere under the conditions of heating temperature: 600 ° C., heating time: 5 hours, heating rate: 50 ° C./hr, cooling rate: furnace cooling. Further, the degreased plate-like molded body was subjected to CIP treatment at a pressure of 300 MPa, then placed on a Pt plate in an alumina mortar and sintered in oxygen at 1105 ° C. for 5 hours. In this way, a crystallographically oriented ceramic was obtained. This is designated as Sample E1.

The crystal-oriented ceramic (sample E1) obtained in this example had a relative density of 95% or more and was sufficiently densified.
For sample E1, the average orientation degree F (100) of {100} planes by the Lotgering method for the plane parallel to the tape plane was calculated using the formula (1). As a result, the pseudo cubic {100} plane was oriented parallel to the tape surface, and the average orientation degree of the pseudo cubic {100} plane by the Lotgering method was 82.1%.

  Further, in this example, for comparison with the sample E1, a crystallographically-oriented ceramic (sample C1) is produced using the first anisotropic shaped powder produced by a method different from the first anisotropic shaped powder used for the sample E1. did. Specifically, the comparatively oriented crystallographic ceramic (sample C1) is prepared by producing the first anisotropic shaped powder without pulverizing the second anisotropic shaped powder, and using the first anisotropic shaped powder. It was produced.

That is, in producing the sample C1, first, Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder (second anisotropic shaped powder) was produced in the same manner as in the case of the sample E1 (see FIG. 1). Then, without the Bi _2.5 Na _3.5 Nb ₅ O ₁₈ milling of powders, with respect to Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder obtained, Na ₂ CO ₃ powder in an amount necessary for the synthesis of NaNbO ₃ (reaction The raw material was added and mixed, and heat treatment was performed at 950 ° C. for 8 hours in a platinum crucible using NaCl as a flux. Further, in the same manner as in the case of the sample E1, the flux is removed and the excess components are dissolved, followed by filtration and washing to obtain a powder (NaNbO ₃ powder) composed of NaNbO ₃ as the first anisotropic shaped powder. It was. This first anisotropic shaped powder was a plate-like powder having a pseudo cubic {100} plane as an orientation plane (maximum plane), an average particle size of 15 μm, and an aspect ratio of about 10 to 20.

Thereafter, in the same manner as in the sample E1, the crystal oriented ceramics having a composition in which 0.0005 mol of Mn is added to 1 mol of {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O _3. Was made. This is designated as Sample C1.
Therefore, the sample C1 was produced in the same manner as the sample E1 except that the second anisotropically shaped powder was not pulverized.
Sample C1 had a relative density of 95% or more and was sufficiently densified.
For sample C1, the average degree of orientation F (100) of the {100} plane by the Lotgering method for the plane parallel to the tape surface was calculated using the formula (1). As a result, the pseudo-cubic {100} plane was oriented parallel to the tape surface, and the average orientation degree of the pseudo-cubic {100} plane by the Lotgering method was 89.6%.

Next, in order to investigate the piezoelectric characteristics and the like of the crystal-oriented ceramics of sample E1 and sample C1,
Piezoelectric elements were fabricated using each crystallographic ceramic (sample E1 and sample C1).
From each crystallographically-oriented ceramic (sample E1 and sample C1), a disk-shaped sample having a top and bottom surface parallel to the tape surface, a thickness of 0.485 mm, and a diameter of 11 mm was prepared by grinding, polishing and processing. Next, Au baking electrode paste (ALP3057 manufactured by Sumitomo Metal Mining Co., Ltd.) was printed and dried on the upper and lower surfaces, followed by baking at 850 ° C. × 10 min using a mesh belt furnace to form an electrode having a thickness of 0.01 mm. . Furthermore, the obtained disk-shaped sample was processed into a diameter of 8.5 mm by cylindrical grinding for the purpose of removing the several micrometer raised portion of the outer periphery of the electrode inevitably formed by printing. Thereafter, two types of piezoelectric elements (sample E2 and sample C2) having a whole surface electrode by performing polarization treatment in the vertical direction were obtained.
Sample E2 is a piezoelectric element manufactured using sample E1 as the crystal-oriented ceramic.
Sample C2 is a piezoelectric element manufactured using Sample C1 as crystal-oriented ceramics.

For the obtained piezoelectric elements (sample E2 and sample C2), the piezoelectric strain constant (d ₃₁ ), the electromechanical coupling coefficient (kp), which is a piezoelectric characteristic, and the relative dielectric constant (ε ₃₃ ^t / ε ₀ ) which is a dielectric characteristic. Was measured at room temperature by the resonant antiresonance method. The results are shown in Table 1.

As is known from Table 1, it can be seen that the piezoelectric elements of Sample E2 and Sample C2 exhibit different piezoelectric characteristics and dielectric characteristics. These piezoelectric elements are produced using two different crystal-oriented ceramics, that is, the sample E1 and the sample C1, and the sample E1 is obtained by pulverizing the raw material (second anisotropically shaped powder) in the manufacturing method. It is different from the sample C1 only in the points.
Therefore, it can be seen that the piezoelectric properties and dielectric properties of the obtained crystal oriented ceramics can be changed by pulverizing the raw material (second anisotropically shaped powder) in the method for producing crystal oriented ceramics.

From the above results, it can be seen that the piezoelectric properties and dielectric properties of the crystallographically-oriented ceramic can be easily changed by grinding the second anisotropic shaped powder.
Although not clearly shown in this example, even if the first anisotropic shaped powder is pulverized instead of the second anisotropic shaped powder, the piezoelectric characteristics and the dielectric characteristics are changed as in this example. Make sure you can.

The electron micrograph which shows the shape of the 2nd anisotropically shaped powder before grinding | pulverization concerning Example 1. FIG. The electron micrograph which shows the shape of the 2nd anisotropically shaped powder after grinding | pulverization concerning Example 1. FIG.

Claims (13)

A method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, wherein a specific crystal plane A of crystal grains constituting the polycrystal is oriented,
A preparatory step of preparing a first anisotropic shaped powder comprising first oriented particles comprising a perovskite type compound and having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented;
A pulverizing step of pulverizing the first anisotropic shaped powder with a jet mill;
Fine powder having an average particle size of 1/3 or less of the first anisotropically shaped powder after the pulverization step and producing the isotropic perovskite type compound by sintering together with the first anisotropically shaped powder Preparing a raw material mixture by mixing the fine powder and the first anisotropic shaped powder,
A molding step of molding the raw material mixture to produce a molded body so that the orientation planes of the first anisotropic shaped powder are oriented in substantially the same direction;
A method for producing a crystallographically-oriented ceramic, comprising a firing step of heating the molded body and sintering the first anisotropically shaped powder and the fine powder.   2. The pulverization of the first anisotropic shaped powder according to claim 1, wherein the first anisotropic shaped powder is formed into a plate shape, and the average particle diameter of the first anisotropic shaped powder is 1 μm to 13 μm. A method for producing a crystallographically-oriented ceramic. A method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, wherein a specific crystal plane A of crystal grains constituting the polycrystal is oriented,
A preparatory step of preparing a first anisotropic shaped powder comprising first oriented particles comprising a perovskite type compound and having an orientation plane in which a crystal plane having lattice matching with the specific crystal plane A is oriented;
Preparing a fine powder having an average particle size of 1/3 or less of the first anisotropic shaped powder and producing the isotropic perovskite compound by sintering together with the first anisotropic shaped powder; A mixing step of mixing the fine powder and the first anisotropically shaped powder to produce a raw material mixture;
A molding step of molding the raw material mixture to produce a molded body so that the crystal planes of the first anisotropic shaped powder are oriented in substantially the same direction;
A heating step of heating the molded body and sintering the first anisotropic shaped powder and the fine powder;
In the preparation step, a second anisotropic shaped powder is prepared which is made of a layered perovskite type compound, and whose crystal face with the smallest surface energy is made of second oriented particles having lattice matching with the oriented surface of the first oriented particles. And preparing a reaction raw material for producing the first anisotropically shaped powder by reacting with the second anisotropically shaped powder after the grinding process of grinding the second anisotropically shaped powder with a jet mill The first anisotropic shaped powder is prepared by performing a heat treatment process for producing the first anisotropic shaped powder by heating the reaction raw material and the second anisotropic shaped powder in a flux. A method for producing a crystallographically-oriented ceramic.   4. The crystallographically-oriented ceramic according to claim 3, wherein the second oriented particles have a lattice plane matching with the oriented surface of the first oriented particles, the largest surface having the largest area on the surface. Manufacturing method. 5. The layered perovskite compound according to claim 3, wherein the layered perovskite compound has the general formula (1): (Bi ₂ O ₂ ) ²⁺ (Bi _0.5 Me _m-1.5 Nb _m O _{3m + 1} ) ²⁻ (where m is 2 A method for producing a crystallographically-oriented ceramic, characterized in that it is a bismuth layered perovskite compound represented by the above integer, Me is one or more selected from Na, K and Li).   6. The method according to claim 3, wherein in the pulverization process, the second anisotropic shaped powder is formed into a plate shape, and the average particle diameter of the second anisotropic shaped powder is 1 μm to 13 μm. And pulverizing the second anisotropically shaped powder. In any one of claims 1 to 6, the first orientation particles consists formula (2) isotropic perovskite type compound represented by ABO _3, A-site element in the general formula (2) is A crystal having one or more selected from K, Na and Li as a main component, and the B site element in the general formula (2) having one or more selected from Nb, Sb and Ta as a main component A method for producing oriented ceramics.   8. The method for producing a crystallographically-oriented ceramic according to claim 1, wherein the oriented surface of the first oriented particles is a pseudo-cubic {100} surface.   The first anisotropically shaped powder and the fine powder have different compositions according to any one of claims 1 to 8, and in the firing step, the anisotropically shaped powder and the fine powder undergo a chemical reaction. A method for producing a crystallographically-oriented ceramic, characterized in that the isotropic perovskite type compound is produced by waking up.   10. The method for producing a crystallographically-oriented ceramic according to claim 1, wherein the polycrystalline body has a degree of orientation of a pseudo-cubic {100} plane by a Lotgering method of 30% or more. 11. The polycrystalline body according to claim 1, wherein the polycrystalline body has a general formula (3): {Lix (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ (Where 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0) as an isotropic perovskite type compound A method for producing a crystallographically-oriented ceramic, characterized in that:   In Claim 11, the polycrystal is a metal element belonging to Group 2 to 15 in the periodic table, a metalloid element, or 1 mol of the isotropic perovskite compound represented by the general formula (3). A method for producing a crystal-oriented ceramic, comprising 0.0001 to 0.15 mol of one or more additive elements selected from a transition metal element, a noble metal element, and an alkaline earth metal element.   13. The additive element according to claim 12, wherein the additive element is one or more elements selected from Li, K, Na, Nb, Ta, and Sb in the isotropic perovskite compound represented by the general formula (3). A method for producing a crystallographically-oriented ceramic, characterized by being substituted and added at a rate of 0.01 to 15 at%.

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