JP2009256147A - Anisotropically formed powder and method for manufacturing crystal oriented ceramic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropically formed powder capable of easily preparing at a low cost, and using as a template when preparing a crystal oriented ceramic, and a method of manufacturing a crystal oriented ceramic using the same. <P>SOLUTION: The invention relates to an anisotropically formed powder composed of a polycrystal having a main phase of an isotropic perovskite-type compound to use as a template for preparing a crystal oriented ceramic in which pseudo-cubic ä100} planes composing the polycrystal are oriented, and to a method of manufacturing the crystal oriented ceramic using the same. The anisotropically formed powder comprises anisotropically formed oriented particles in which oriented planes are formed by developing ä010} planes. The oriented particles comprise a laminar compound represented by general formula (1): A<SB>4</SB>B<SB>6</SB>O<SB>17</SB>, or general formula (2): AB<SB>3</SB>O<SB>8</SB>, wherein the A site element is at least K as a major constituent, and the B site element is at least Nb as a major constituent in general formulae (1) and (2). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an anisotropic shape used for producing a crystal-oriented ceramic comprising a polycrystal having an isotropic perovskite compound as a main phase and having a specific crystal plane of crystal grains constituting the polycrystal. The present invention relates to a powder and a method for producing a crystallographically-oriented ceramic using the anisotropically shaped powder.

  Polycrystalline materials made of ceramics are used for various sensors such as temperature, heat, gas, and ions. It is also used for electronic circuit components such as capacitors, resistors, and integrated circuit substrates, optical or porcelain recording elements, and the like. In particular, polycrystals made of ceramics with piezoelectric effect (hereinafter referred to as “piezoelectric ceramics” as appropriate) are high performance, have a high degree of freedom in shape, and are relatively easy to design materials, so they are widely used in the fields of electronics and mechatronics. It is applied in.

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 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 relatively high piezoelectric properties among piezoelectric materials not containing lead, and is used for sonar. Some solid solutions of BaTiO3 and other lead-free perovskite compounds (such as BNT) exhibit relatively high piezoelectric characteristics. However, these lead-free piezoelectric ceramics have a problem that the piezoelectric characteristics are low as compared with PZT.

  In order to solve such problems, various piezoelectric ceramics have been proposed. For example, there are isotropic perovskite-type potassium sodium niobate niobates that exhibit relatively high piezoelectric properties among non-lead-based materials and piezoelectric ceramics made of a solid solution thereof (see 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 spontaneous polarization preferentially oriented in one plane has been developed (see Patent Document 7).
In general, it is known that piezoelectric characteristics and the like differ 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. As disclosed in Patent Document 7, according to a method in which a plate-like powder having a predetermined composition is used as a reactive template, and the plate-like powder and raw material powder are sintered to orient a specific crystal plane. A high-performance crystal-oriented ceramic in which a specific crystal plane is oriented with a high degree of orientation can be produced.

As shown in FIGS. 1 to 4, the crystal-oriented ceramic can be produced, for example, as follows.
That is, first, as shown in FIG. 1, an anisotropic plate-like powder 1 having a predetermined composition is prepared as a reactive template. In addition, a raw material powder (fine powder) 2 is prepared which reacts with the plate-like powder 1 during firing to produce an isotropic perovskite type compound. Next, a solvent, a binder, a plasticizer, a dispersing agent, and the like are added to and mixed with the plate-like powder 1 and the raw material powder 2 to produce a slurry 3.
In the slurry 3, the plate-like powder 1 and the raw material powder 2 are dispersed in a dispersion medium 4 composed of a solvent, a binder, a plasticizer, a dispersion material, and the like.

Next, as shown in FIG. 2, the slurry 3 is formed into a sheet shape, for example, to produce a formed body 5. At this time, as shown in the figure, the anisotropically shaped plate-like powder 1 is aligned in substantially the same direction in the molded body 5 by the shear stress applied during molding.
Next, the molded body 5 is heated and sintered. At this time, as shown in FIG. 3, in the green compact 6 being sintered, the plate-like powder 1 becomes a reactive template and reacts with the surrounding raw material powder 2 to produce the isotropic perovskite compound. While the plate-like powder 1 grows. Further, when the sintering proceeds, the plate-like powder 1 further grows while reacting with the raw material powder 2, and as shown in FIG. 4, crystal oriented ceramics comprising crystal particles (oriented particles) 7 in which specific crystal planes are oriented. 8 can be obtained.

Isotropic perovskite potassium sodium niobate represented by the general formula ABO ₃ (A-site element is Na, K, etc., B-site element is Nb, etc.) has a very small crystal lattice anisotropy. It is difficult to directly synthesize the anisotropically shaped powder having a plane as an orientation plane.
On the other hand, for example, the general formula (Bi ₂ O ₂ ) ²⁺ (Bi _0.5 Me _m-1.5 Nb _m O _{3m + 1} ) ²⁻ (where m is an integer of 2 or more, Me is Li, K, and Na And a layered perovskite type compound such as Sr ₂ Nb ₂ O ₇ has a large crystal lattice anisotropy, and is composed of such a layered perovskite type compound and orients a crystal plane with a small surface energy. The anisotropically shaped powder used as the surface can be synthesized relatively easily. And since the lattice matching with said isotropic perovskite type | mold potassium sodium niobate is favorable, it can be used as a template for manufacturing a crystal-oriented ceramic.

However, the layered perovskite compound contains an element (Bi, Sr, etc.) other than the constituent elements (K, Na, Nb, etc.) constituting the target isotropic perovskite potassium sodium niobate, and has an anisotropic shape. These elements remain in the powder and the crystal-oriented ceramic. Therefore, there is a possibility that the most desirable composition cannot be realized, and there is a possibility that various characteristics such as piezoelectric characteristics are deteriorated due to the irreversibly contained A site element and B site element.
In order to avoid this, an anisotropic shaped powder composed of the above-mentioned layered perovskite type compound is used as a reactive template, and this and the reaction raw material are heated in a flux, whereby a specific crystal plane becomes an orientation plane. A method for synthesizing the anisotropically shaped powder has also been developed. This makes it possible to synthesize anisotropically shaped powders such as NaNbO ₃ , KNbO ₃ , (K _1-y Na _y ) NbO ₃ (0 <y <1), which are a kind of isotropic perovskite compounds.

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

  However, the conventional anisotropically shaped powder has a very complicated synthesis process, and the productivity of the anisotropically shaped powder is reduced. For this reason, the productivity of the crystallographically-oriented ceramic is also lowered, which increases the manufacturing cost.

  The present invention has been made in view of such a conventional problem, and can be produced simply and at low cost, and an anisotropically shaped powder that can be used as a template for producing crystallographically oriented ceramics and the use thereof An object of the present invention is to provide a method for producing a crystallographically-oriented ceramic.

1st invention is used as a template for manufacturing the crystal orientation ceramics which consist of the polycrystal which has an isotropic perovskite type compound as a main phase, and the pseudo cubic {100} plane which comprises this polycrystal body orientates. An anisotropically shaped powder,
The anisotropically shaped powder is composed of anisotropically oriented particles whose {010} plane is developed to form an oriented surface,
The oriented particle is a layered compound represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ (however, in the general formulas (1) and (2), the A site element is at least K). And the B-site element is at least Nb as a main component. (Claim 1)

The layered compound represented by the general formula (1) or the general formula (2) does not necessarily have good lattice matching with the pseudocubic {100} plane of the isotropic perovskite compound, but the layered compound The anisotropically shaped powder made of a compound can be used as a template for the crystallographically-oriented ceramic. This is because the NbO ₆ unit existing in the layered compound is converted into a perovskite ordered NbO ₆ unit structure when producing a crystallographically-oriented ceramic using the anisotropically shaped powder. This is presumably because the pseudo-cubic {100} plane of the crystalline perovskite compound grows preferentially to produce the above-mentioned crystallographically-oriented ceramic.

  The layered compound represented by the general formula (1) or the general formula (2) has a large crystal lattice anisotropy. Therefore, it is possible to synthesize an anisotropically shaped powder having a crystal plane ({010} plane) having a small surface energy as an orientation plane (maximum plane) relatively easily. The layered compound can be easily produced by using an oxide, carbonate, nitrate, or the like containing the component element as a raw material and heating the raw material together with a liquid or a substance that becomes liquid by heating. This is because when the raw material is heated in a liquid phase in which atoms are easily diffused, a surface with a small surface energy ({010} surface) develops preferentially, and the anisotropically shaped powder can be obtained.

  The anisotropically shaped powder composed of the layered compound can be produced only with the component elements constituting the isotropic perovskite compound, such as K and Nb. That is, it is possible to prevent an element such as Bi or Sr that can lower the piezoelectric properties of the isotropic perovskite compound from remaining in the crystal-oriented ceramic or the anisotropically shaped powder.

  As described above, according to the present invention, it is possible to provide an anisotropically shaped powder that can be produced easily and at low cost and can be used as a template for producing crystal-oriented ceramics.

According to a second aspect of the present invention, there is provided a method for producing a crystal-oriented ceramic comprising a polycrystal having an isotropic perovskite compound as a main phase, wherein a pseudo cubic {100} plane constituting the polycrystal is oriented.
A layered compound represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ (however, in the general formulas (1) and (2), the A site element contains at least K as a main component, B-site element is composed of at least Nb as a main component), and an anisotropically shaped powder comprising anisotropically oriented particles whose {010} plane develops to form an oriented surface; A mixing step of obtaining a raw material mixture by mixing fine powders having an average particle size of 3 or less and forming the isotropic perovskite compound by sintering together with the anisotropically shaped powder;
A molding step of molding the raw material mixture to obtain a molded body so that the oriented surfaces of the anisotropically shaped powder are oriented in substantially the same direction; and
A method for producing a crystallographically-oriented ceramic, comprising: a step of heating the shaped body and sintering the anisotropically-shaped powder and the fine powder to obtain the crystallographically-oriented ceramic. 4).

In the second aspect of the invention, the mixing step, the forming step, and the firing step are performed to form a polycrystal having an isotropic perovskite compound as a main phase, and the pseudomorph constituting the polycrystal. A crystallographically oriented ceramic in which the cubic {100} plane is oriented can be produced.
In the mixing step, the anisotropically shaped powder of the first invention is used.
Therefore, in the firing step, the anisotropically shaped powder and the fine powder are sintered, the isotropic perovskite type compound is generated, and the crystal oriented ceramics in which the pseudo cubic {100} plane is oriented is produced. Can be manufactured.
In the firing step, the NbO ₆ unit present in the layered compound is converted into a perovskite ordered NbO ₆ unit structure. At this time, the pseudo cubic {100} plane of the isotropic perovskite compound is preferential. It is considered that the above-mentioned crystallographically-oriented ceramic can be produced.

  Since the above-mentioned crystallographically-oriented ceramic is made of a polycrystal having the isotropic perovskite type compound as a main phase, it can exhibit excellent piezoelectric characteristics among non-leaded piezoelectric ceramics. In addition, the above-mentioned crystal-oriented ceramics have superior piezoelectric properties compared to non-oriented sintered bodies having the same composition because specific crystal faces of each crystal grain constituting the polycrystal are oriented in one direction. Can show.

In the production method of the present invention, the mixing step, the forming step, and the firing step are performed using the anisotropically shaped powder. Therefore, even the above-mentioned isotropic perovskite type crystal-oriented ceramics having a complicated composition can be produced.
Moreover, in the said 2nd invention, the said anisotropically shaped powder which can be manufactured simply and cheaply is used. Therefore, the above-mentioned crystallographically-oriented ceramic can be manufactured easily and inexpensively.

Next, a preferred embodiment of the present invention will be described.
The anisotropically shaped powder is made of a polycrystal having an isotropic perovskite compound as a main phase, and is used as a template for producing a crystallographically-oriented ceramic in which the pseudo-cubic {100} plane constituting the polycrystal is oriented. Used. Specifically, the crystal oriented ceramics can be manufactured by performing the mixing step, the forming step, and the firing step, for example.

Here, “isotropic” means that when the perovskite structure ABO ₃ is expressed by a pseudo cubic basic lattice, the relative ratio of axial lengths a, b, c is 0.8 to 1.2, and the axial angle α , Β, and γ are in the range of 80 to 100 °. The crystal plane is a pseudo-cubic {100} plane.
“Pseudocubic {100} plane is oriented” means that the crystal grains are arranged so that the pseudocubic {100} planes of the perovskite compound are parallel to each other (hereinafter, this state is referred to as It is referred to as “plane orientation” as appropriate.

“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.
In the case where a specific crystal plane is plane-oriented, the degree of plane orientation can be represented by an average degree of orientation F (HKL) by the Lotgering method expressed by the following equation (1).

  In Equation 1, ΣI (hkl) is the sum of X-ray diffraction intensities of all crystal planes (hkl) measured for the crystal oriented ceramics, and ΣI0 (hkl) has the same composition as the crystal oriented ceramics. It is the sum total of the X-ray diffraction intensities of all crystal planes (hkl) measured for non-oriented piezoelectric ceramics. Σ'I (HKL) is the sum of X-ray diffraction intensities of specific crystal planes (HKL) that are crystallographically equivalent measured for crystal-oriented ceramics, and Σ'I0 (HKL) is the crystal orientation. It is the sum total of X-ray diffraction intensities of specific crystal planes (HKL) crystallographically equivalent measured for non-oriented piezoelectric ceramics having the same composition as the 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.

Examples of the isotropic perovskite-type compound of the crystal-oriented ceramic produced using the anisotropically shaped powder include, for example, the general formula ABO ₃ (where the A-site element is mainly composed of K and / or Na, and the B-site element) Is a compound represented by the formula (Nb as a main component). In the above general formula, the A site and / or the B site may contain an additive element described later as a subcomponent in addition to the above-mentioned main component elements.
Specifically, as the compound represented by the above general formula ABO ₃ , for example, potassium sodium niobate (K _{1 -y} Na _y ) NbO ₃ (0 ≦ y ≦ 1) is used as a basic composition, and the A site element (K , Na) partially substituted with a predetermined amount of Li, or B site element (Nb) partially substituted with a predetermined amount of Ta and / or Sb, or A site element (K, Na) And a part of the B-site element (Nb) is substituted with a predetermined amount of Ta and / or Sb.

The isotropic perovskite type compound represented by the general formula _{(3): {Li x (} K 1-y Na y) 1-x} a (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, 0.95 ≦ a ≦ 1.05) (claims) 3. Claim 6).
In this case, the above-mentioned crystallographically-oriented ceramic having excellent piezoelectric characteristics, dielectric characteristics and the like can be manufactured. In this case, the advantage of using the anisotropically shaped powder becomes remarkable.
That is, the isotropic perovskite type compound itself represented by the general formula (3) itself has, for example, a plurality of compounds having a simple composition containing component elements of the target composition so as to have a target stoichiometric ratio. It can be manufactured by mixing, forming and calcining the mixture, crushing, and then re-molding and sintering the crushed powder. However, with such a manufacturing method, it is very difficult to manufacture a crystallographically-oriented ceramic in which specific crystal faces of each crystal grain are oriented.
In the present invention, as described above, the anisotropically shaped powder is used. Therefore, the isotropic perovskite compound having a complex composition represented by the general formula (3) can be synthesized and sintered, and the anisotropically shaped powder becomes a template and a reactive template. The above-mentioned crystallographically-oriented ceramic in which specific crystal planes ({100} planes) of the crystal grains are oriented can be produced.

Further, when the compound represented by the general formula (3) is applied to the composition formula ABO ₃ having a perovskite structure, the composition ratio of the A site atom and the B site atom is ± 5 with respect to 1: 1, respectively. The composition ratio can be shifted to%. In order to finally reduce the number of lattice defects in the crystal of the crystal-oriented ceramic and to obtain more excellent piezoelectric characteristics, the composition is preferably up to ± 3%. That is, in the general formula (3), 0.95 ≦ a ≦ 1.05, and preferably 0.97 ≦ a ≦ 1.03.

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. In the compound represented by the general formula (3), it is sufficient that at least one of K or Na is contained 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 (3). 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 ₃₃ 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 ₃₃ 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 more 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 and enables firing with less voids. If the value of x exceeds 0.2, the piezoelectric properties (piezoelectric d ₃₃ 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 above-mentioned crystal oriented ceramic, since the raw material does not include the lightest compound containing Li, such as LiCO ₃ , the raw materials are mixed and the above crystal oriented ceramics are 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 (3). 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.
Moreover, 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 (3) 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.

Next, the crystallographically-oriented ceramic can be manufactured by performing, for example, a mixing step, a forming step, and a firing step.
In the mixing step, the {010} plane is developed to form an oriented oriented particle that forms an oriented surface, and is represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ . An anisotropically shaped powder comprising a layered compound represented by the formula (provided that in the general formulas (1) and (2), the A-site element contains at least K as a main component and the B-site element contains at least Nb as a main component); The raw material mixture is obtained by mixing with the fine powder that has an average particle size of 1/3 or less of the rectangular powder and produces the above isotropic perovskite compound by sintering together with the anisotropic shaped powder.

The anisotropically shaped powder is a layered compound represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ (however, the A site element in the general formulas (1) and (2) is At least K as a main component and B-site element as a main component at least Nb.
“Anisotropic shape” means that the dimension in the longitudinal direction, which is a direction substantially perpendicular to the dimension in the width direction or the thickness direction, is larger. Specifically, shapes such as a plate shape, a column shape, a scale shape, and a needle shape are preferable examples.
As the oriented particles, it is preferable to use those having a shape that can be easily oriented in a certain direction during the molding step described later. For this reason, the oriented particles preferably have an average aspect ratio of 3 or more. When the average aspect ratio is less than 3, it becomes difficult to orient the anisotropically shaped powder in one direction in the molding step described later. In order to obtain the above-mentioned crystal-oriented ceramic with a higher degree of orientation, the aspect ratio of the oriented particles is more preferably 5 or more. The average aspect ratio is an average value of the maximum dimension / minimum dimension of the oriented particles.

  In addition, as the average aspect ratio of the oriented particles increases, it becomes easier to orient the 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.

  Further, in the firing step described later, since the anisotropically shaped powder and the fine powder react and sinter to form crystal particles, if the oriented particles of the anisotropically shaped powder are too large, the crystal particles May increase and the strength of the obtained crystallographically-oriented ceramic may be reduced. Accordingly, the maximum dimension in the longitudinal direction of the oriented particles is preferably 30 μm or less. More preferably, it is 20 μm or less, and further preferably 15 μm or less. Further, if the oriented particles are too small, the crystal particles become small, and the piezoelectric performance of the obtained crystal oriented ceramics may be lowered. Therefore, the maximum dimension in the longitudinal direction of the oriented particles is preferably 0.5 μm or more. More preferably, it is 1 μm or more, and more preferably 2 μm or more.

The anisotropically shaped powder is made from an oxide, carbonate, nitrate or the like containing a component element having the composition represented by the general formula (1) or the general formula (2) as a raw material. It can manufacture easily by heating with the substance used as. At this time, when the raw material is heated in a liquid phase in which atoms are easily diffused, a plane with a small surface energy ({010} plane) develops preferentially, and the anisotropic shape having this as an orientation plane (maximum plane). A powder can be obtained. The average aspect ratio and average particle size of the anisotropically shaped powder can be controlled by selecting synthesis conditions, classification after synthesis, and / or grinding.
More specifically, an appropriate flux (for example, KCl or a mixture of NaCl and KCl) is added to the above-mentioned raw material and heated at a predetermined temperature (flux method), or an anisotropic shaped powder to be produced The anisotropically shaped powder can be produced by a method of heating an amorphous powder having the same composition together with an alkaline aqueous solution in an autoclave (hydrothermal synthesis method).

The layered compound is preferably K ₄ Nb ₆ O ₁₇ or KNb ₃ O ₈ (claims 2 and 5).
In this case, the degree of orientation of the crystal oriented ceramics to be produced can be further improved.

Next, the fine powder has an average particle size of 1/3 or less of the anisotropically shaped powder.
When the particle size of the fine powder exceeds 1/3 of the particle size of the anisotropically shaped powder, in the molding step, the oriented surface of the anisotropically shaped powder is oriented in substantially the same direction, It may be difficult to form the raw material mixture. More preferably, it is 1/4 or less, and further preferably 1/5 or less. The particle size of the fine powder and the anisotropic shaped powder can be compared by comparing the average particle size of the fine powder and the average particle size of the anisotropic shaped powder. The particle diameter of the anisotropically shaped powder and the particle diameter of the fine powder are both the longest diameter.

  The composition of the fine powder can be determined according to the composition of the anisotropically shaped powder and the composition of the isotropic perovskite compound represented by the general formula (3) to be produced. As the fine powder, a powder that reacts with the anisotropically shaped powder by sintering together with the anisotropically shaped powder to produce the desired isotropic perovskite compound represented by, for example, the general formula (3). Can be used. 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.

  As the fine powder, one or more calcined powders selected from Li source, K source, Na source, Nb source, Ta source, and Sb source can be used. As each element source described above, a compound containing at least one of these elements can be employed. The blending ratio of each element source can be determined from the composition of the perovskite type compound represented by the general formula (1) and the composition of the anisotropically shaped powder.

In the mixing step, the anisotropically shaped powder and the fine powder have a stoichiometric ratio that produces the desired isotropic perovskite compound, for example, a chemistry that produces a compound represented by the general formula (3). Mix in stoichiometric ratio. At this time, the blending ratio of the anisotropically shaped powder and the fine powder is a molar ratio, anisotropically shaped powder: fine powder = 0.02 to 0.10: 0.98 to 0.90 (however, anisotropic The total of the shape powder and the fine powder is preferably 1 mol).
If the anisotropically shaped powder is less than 0.02 or the fine powder exceeds 0.98 in the above blending ratio (molar ratio), the degree of orientation is increased to a practically sufficient level for applications such as piezoelectric materials. Can be difficult.
On the other hand, when the anisotropically shaped powder exceeds 0.10 or the fine powder is less than 0.90, there is a possibility that a crystal-oriented ceramic with high density cannot be obtained. For this reason, the piezoelectric properties of the crystal-oriented ceramic may be insufficient.

  In the mixing step, the anisotropically shaped powder and the fine powder may be mixed dry, or may be performed wet by adding an appropriate organic solvent such as water or alcohol. Further, at this time, a binder, a plasticizer, and the like can be added as necessary.

Next, in the molding step, the raw material mixture is molded to obtain a molded body so that the oriented surfaces of the anisotropically shaped powder are oriented in substantially the same direction.
Any molding method may be used as long as the anisotropically shaped powder can be oriented. Specific examples of a molding method for orienting the anisotropically shaped powder include a doctor blade method, a press molding method, and a rolling method. According to these molding methods, the anisotropically shaped powder can be oriented in substantially the same direction within the molded body due to shear stress acting on the anisotropically shaped powder.

  In the firing step, by heating the shaped body, at least the anisotropically shaped powder and the fine powder are reacted and sintered to obtain the crystal-oriented ceramic. In the firing step, sintering proceeds by heating the shaped body, and the crystal-oriented ceramic made of a polycrystal having the isotropic perovskite compound as a main phase can be produced.

  The heating temperature in the firing step is an anisotropically shaped powder, a fine powder, and an attempt to produce so that the reaction and / or sintering can proceed efficiently and a reactant having the desired composition is generated. The optimum temperature can be selected according to the composition of the crystal oriented ceramics. Specifically, it can be performed at a temperature of 900 ° C. to 1300 ° C., for example.

Example 1
Next, examples of the present invention will be described.
This example is composed of a polycrystal having an isotropic perovskite type compound ({Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ ) as a main phase, and constitutes the polycrystal. This is an example of producing a crystallographically-oriented ceramic in which the pseudo-cubic {100} plane is oriented.

In this example, a crystallographically-oriented ceramic is manufactured by performing a mixing step, a forming step, and a firing step.
In the mixing step, an anisotropically shaped powder composed of anisotropically oriented particles composed of the layered compound K ₄ Nb ₆ O ₁₇ , which develops a {010} plane to form an oriented surface, and 1 of this anisotropically shaped powder The raw material mixture is obtained by mixing with the fine powder having an average particle size of / 3 or less and forming the isotropic perovskite compound by sintering together with the anisotropically shaped powder.
In the forming step, the raw material mixture is formed so that the oriented surface of the anisotropically shaped powder is oriented in substantially the same direction to obtain a shaped body.
In the firing step, the shaped body is heated and the anisotropically shaped powder and the fine powder are sintered to obtain a crystallographically oriented ceramic.
Hereinafter, the manufacturing method of the crystallographically-oriented ceramic of this example will be described in detail.

"Production of anisotropically shaped powder"
First, a plate-like anisotropic shaped powder made of K ₄ Nb ₆ O ₁₇ was synthesized as follows.
Specifically, first, K ₂ CO ₃ powder and Nb ₂ O ₅ powder were weighed at a stoichiometric ratio such that the composition was K ₄ Nb ₆ O ₁₇ , and these were wet mixed. 50 parts by weight of KCl was added as a flux to 100 parts by weight of the obtained mixed raw material, and dry mixed for 1 hour.
Next, the obtained mixture was put in 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 1050 ° C. × 2 h to obtain K ₄ Nb ₆ O. ₁₇ were 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 washing with hot water, and classification and pulverization were performed using a jet mill to obtain K ₄ Nb ₆ O ₁₇ powder (anisotropically shaped powder). The obtained anisotropically shaped powder is a plate-like powder having a {010} plane as an orientation plane (maximum plane), an average particle diameter (average of the maximum diameter) of 10 μm, and an aspect ratio of about 5 to 15. there were.

Next, the full width at half maximum by the rocking curve method was measured for the orientation plane ({010} plane) of the obtained anisotropically shaped powder.
Specifically, first, the anisotropically shaped powder was put into ethanol. The amount of anisotropically shaped powder charged was 3 wt%. Next, using an ultrasonic disperser (SUS-103 manufactured by Shimadzu Rika Co., Ltd.), the anisotropically shaped powder was uniformly dispersed at 28 kHz for 2 minutes to obtain a dispersion. Next, the dispersion was dropped onto a glass substrate having a smooth surface and then dried. Thereby, the anisotropic shaped powder was arranged in a single layer on the glass substrate.
Next, the X-ray diffraction intensity of the anisotropically shaped powder arranged on the substrate was measured. The X-ray diffraction intensity is measured by using an X-ray diffractometer (RINT-TTR manufactured by Rigaku Corporation) and by using X-ray diffraction (2θ method) under the condition of CuKα ray and 50 kV / 300 mA at an arbitrary angle of 0 to 0. It was performed in a range of 180 ° (20 ° to 50 ° in this example). Next, in the obtained X-ray diffraction pattern, X-ray diffraction (θ method) is performed with the θ angle fixed at the position of the peak derived from the {010} plane, and the maximum intensity of the obtained chevron waveform (rocking curve) is The peak width (full width) at half the intensity was determined. This was defined as the half width. As a result, the half-value width was 1 °, and it was found that the anisotropically shaped powder produced in this example has very good plane orientation.

"Preparation of fine powder"
Na ₂ CO ₃ powder with a purity of 99.99% or more, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and Sb ₂ O ₅ powder are converted into the desired crystal-oriented ceramics. Composition {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ 1 mol stoichiometric amount obtained by subtracting 0.05 mol of the anisotropically shaped powder composition K ₄ Nb ₆ O ₁₇ Weighing was performed in a theoretical ratio, and wet mixing was performed for 20 hours with a ZrO ₂ ball using an organic solvent as a medium. Thereafter, calcined for 5 hours at a temperature of 750 ° C., and further wet pulverized 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 size of about 0.5 μm. .

"Production of crystallographically oriented ceramics"
Next, the anisotropically shaped powder and the fine powder are mixed at a blending ratio that produces the composition of the desired crystallographically-oriented ceramic ({Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ ). (Mixing step). At this time, 5 at% (atomic percentage) of the K (A site element) amount in the composition of the target crystallographic ceramic ({Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ ) Was blended in such a proportion that it was supplied from K in the anisotropically shaped powder (K ₄ Nb ₆ O ₁₇ ). Furthermore, 10 parts by weight of polyvinyl butyral (PVB) resin as a binder and 5 parts by weight of butyl phthalate as a plasticizer are added to 100 parts by weight of a mixture of anisotropically shaped powder and fine powder. The mixture was mixed for 1 hour to obtain a slurry-like raw material mixture.

Next, the raw material mixture was formed into a tape having a thickness of 100 μm using a doctor blade device to obtain a formed body (forming step). In this molded body, anisotropic shaped powders composed of plate-like oriented particles are oriented in substantially the same direction.
Subsequently, the obtained tape-shaped molded body was laminated, pressure-bonded and rolled to obtain a plate-shaped molded body having a thickness of 1.5 mm. Subsequently, the obtained plate-shaped molded body was degreased. Degreasing was carried out in the air under the conditions of heating temperature: 600 ° C., heating time: 5 hours, heating rate 50 ° C./hr, cooling rate: furnace cooling. Furthermore, the CIP process was performed on the plate-shaped molded body after degreasing at a pressure of 300 MPa.

Next, the molded body obtained as described above is fired to produce a polycrystalline body.
In this firing process, three processes were performed: a temperature raising process, a holding process, and a cooling process.
That is, first, the compact was placed in a heating furnace controlled in an oxygen atmosphere, and the temperature in the heating furnace was raised to 1105 ° C. at a temperature raising rate of 200 ° C./h (temperature raising process). Next, this temperature of 1105 ° C. was held for 5 hours (holding process). Next, it was cooled to room temperature at a cooling rate of 200 ° C./h (cooling process).
In this way, a crystallographically oriented ceramic was obtained. This is designated as Sample E1.

Next, the degree of orientation of the {100} plane (average degree of orientation F (100)) was measured for the obtained crystallographically-oriented ceramic (sample E1).
Specifically, using the X-ray diffractometer (RINT-TTR manufactured by Rigaku Corporation), the X-ray diffraction intensity of the sample E1 was measured under the conditions of Cu-Kα and 50 kV / 300 mA. The average orientation degree F (100) by the Lotgering method was calculated from the equation. As a result, the average orientation degree of the sample E1 was 50%.

In addition, the non-oriented piezoelectric ceramic used for calculation of the average degree of orientation F of the crystal oriented ceramics by the Lotgering method was produced as follows.
That is, first, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, so as to have a composition of {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ , Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and Sb ₂ O ₅ powder were weighed, and wet mixed for 20 hours with ZrO ₂ balls using an organic solvent as a medium. Thereafter, calcination was performed at 750 ° C. for 5 hours, and further, wet pulverization was performed for 20 hours with a ZrO ₂ ball using an organic solvent as a medium to obtain a calcined powder having an average particle size of about 0.5 μm. Furthermore, using an organic solvent as a medium, 10 parts by weight of polyvinyl butyral (PVB) resin as a binder and 5% by weight of dibutyl phthalate as a plasticizer with respect to 100 parts by weight of the total amount of each powder (fine powder) described above. Part of the mixture was added, and wet mixing was performed with ZrO ₂ balls to obtain a slurry-like raw material mixture.

  Next, the raw material mixture was formed into a tape shape having a thickness of 100 μm using a doctor blade device to obtain a non-oriented formed body (non-oriented formed body). Next, the non-oriented molded body was laminated, pressure-bonded, degreased, and fired under the same conditions as the sample E1, thereby producing non-oriented piezoelectric ceramics. The X-ray diffraction intensity of this non-oriented piezoelectric ceramic was also measured, and the average degree of orientation F (100) of the crystal-oriented ceramic (sample E1) by the Lotgering method was calculated from the equation (1).

In this example, as described above, the crystallographically-oriented ceramic was manufactured by performing the mixing step, the forming step, and the firing step. In the mixing step, anisotropic shaped powder made of anisotropically oriented particles made of layered compound K ₄ Nb ₆ O ₁₇ and having a {010} plane developed to form an oriented surface is used.
Therefore, in the firing step, while producing and producing an isotropic perovskite compound while the anisotropically shaped powder and fine powder react and sinter, produce crystal oriented ceramics in which the pseudo cubic {100} plane is oriented. Can do. In the firing step, the NbO ₆ unit present in the layered compound is converted into a perovskite ordered NbO ₆ unit structure, and at this time, the pseudocubic {100} plane of the isotropic perovskite compound grows preferentially. It is considered that crystal-oriented ceramics can be produced.
Actually, in this example, it was possible to produce a crystallographically-oriented ceramic having an orientation degree that can be practically used with an average orientation degree of 50%.

  In addition, since the crystallographically-oriented ceramic of this example is made of a polycrystal having an isotropic perovskite compound as a main phase, it can exhibit excellent piezoelectric characteristics among non-leaded piezoelectric ceramics. In addition, the crystal-oriented ceramic is a non-oriented sintered body having the same composition because the pseudo-cubic {100} planes of the crystal grains constituting the polycrystal are oriented in one direction (average orientation degree 50%). In comparison, excellent piezoelectric characteristics can be exhibited.

Moreover, in this example, the said mixing process, the said shaping | molding process, and the said baking process are performed using anisotropically shaped powder. Therefore, even an isotropic perovskite type crystal-oriented ceramic having a complicated composition of {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ can be produced. It was.
In the present example, the anisotropically shaped powder, which is a layered compound K ₄ Nb ₆ O _17, which can be produced easily and inexpensively, is used. Therefore, the above-mentioned crystallographically-oriented ceramic can be manufactured easily and inexpensively.

  As described above, according to the present example, the anisotropically-shaped powder that can be produced easily and at low cost and can be used as a template for producing crystal-oriented ceramics, and a method for producing crystal-oriented ceramics using the same Can be provided.

(Example 2)
In this example, a crystal-oriented ceramic similar to that in Example 1 is produced using an anisotropically shaped powder (KNb ₃ O ₈ ) having a composition different from that in Example 1.
First, a plate-like powder made of KNb ₃ O ₈ was produced as an anisotropic shaped powder as follows.
That is, first, K ₂ CO ₃ powder and Nb ₂ O ₅ powder were weighed at a stoichiometric ratio such that the composition was KNb ₃ O ₈ , and these were wet mixed. 50 parts by weight of KCl was added as a flux to 100 parts by weight of the obtained mixed 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 1150 ° C. × 2 h to obtain KNb ₃ O ₈ Synthesis was performed. 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 washing with hot water, and classification and pulverization were performed using a jet mill to obtain a KNb ₃ O ₈ powder (anisotropically shaped powder). The obtained KNb ₃ O ₈ powder is a plate-like powder having a {010} plane as an orientation plane (maximum plane), an average particle diameter (average of the maximum diameter) of 10 μm, and an aspect ratio of about 5 to 15. there were.

  Next, with respect to the orientation plane ({010} plane) of the obtained anisotropically shaped powder, the full width at half maximum was measured by the rocking curve method in the same manner as in Example 1. As a result, the half-value width was 1 °, and it was found that the anisotropically shaped powder produced in this example has very good plane orientation.

Next, a fine powder was produced in the same manner as in Example 1.
That is, Na ₂ CO ₃ powder having a purity of 99.99% or more, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and Sb ₂ O ₅ powder are converted into the target crystals. Composition of oriented ceramics {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ 1 mol stoichiometry to obtain a composition obtained by subtracting 0.05 mol of the anisotropically shaped powder composition KNb ₃ O ₈ After weighing in a theoretical ratio and performing wet mixing for 20 hours with a ZrO ₂ ball using an organic solvent as a medium, in the same manner as in Example 1, the mixture is calcined and further subjected to wet pulverization, whereby the average particle size is about 0. 0. A 5 μm calcined powder (fine powder) was obtained.

Next, the anisotropically shaped powder and the fine powder were mixed in the same manner as in Example 1 to obtain a slurry-like raw material mixture (mixing step).
Further, in the same manner as in Example 1, the raw material mixture was formed into a tape shape, and the formed body was laminated, pressed and rolled to obtain a plate-like formed body having a thickness of 1.5 mm. This molded body was degreased and CIP treated, and then fired in the same manner as in Example 1 to obtain a crystallographically oriented ceramic. This is designated as Sample E2.

  With respect to the obtained crystallographically-oriented ceramic (sample E2), the orientation degree of the {100} plane (average orientation degree F (100)) was measured in the same manner as in Example 1. As a result, the average orientation degree of Sample E2 was 55%.

In this example, a crystallographically-oriented ceramic was produced using an anisotropically shaped powder made of a layered compound KNb ₃ O ₈ . Even in this case, it was possible to produce a crystallographically-oriented ceramic having an orientation degree of an average orientation degree of 55% which can be sufficiently put into practical use.
Then, anisotropically shaped powder comprising KNb ₃ O _8, since it is possible to easily and inexpensively manufactured, the crystal oriented ceramics of this example can be manufactured in a simple and low cost.

(Comparative example)
Next, a comparative example in which a crystallographically-oriented ceramic is produced using a plate-like powder made of NaNbO ₃ as an anisotropic shaped powder will be described.
Synthesized.
First, a plate-like powder made of NaNbO ₃ was produced as an 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. . 50 parts by weight of NaCl as a flux was added to 100 parts by weight of the obtained mixed raw material, and dry mixed for 1 hour. Next, the obtained mixture was put in 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 washing with hot water to obtain Bi _2.5 Na _3.5 Nb ₅ O ₁₈ 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, an amount of Na ₂ CO ₃ powder necessary for the synthesis of NaNbO ₃ was added to the Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder and mixed. Next, this mixture was heat-treated at 950 ° C. for 8 hours in a platinum crucible using NaCl as a flux. 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 (anisotropically shaped powder) and washed with ion exchange water at 80 ° C. In this way, NaNbO ₃ powder as an anisotropically shaped powder was obtained.
The obtained NaNbO3 powder was a plate-like powder having a pseudo cubic {100} plane as the maximum plane (orientation plane), an average particle diameter (average of the maximum diameter) of 15 μm, and an aspect ratio of about 10 to 20. It was.

  For the orientation plane ({100} plane) of the obtained anisotropically shaped powder, the full width at half maximum was measured by the rocking curve method in the same manner as in Example 1. As a result, the half width was 9 °.

Next, a fine powder was produced in the same manner as in Example 1.
That is, Na ₂ CO ₃ powder having a purity of 99.99% or more, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and Sb ₂ O ₅ powder are converted into the target crystals. Composition of oriented ceramics {Li _0.065 (K _0.45 Na _0.55 ) _0.935 } (Nb _0.83 Ta _0.09 Sb _0.08 ) O ₃ 1 mol stoichiometric ratio to obtain a composition obtained by subtracting 0.05 mol of anisotropic shaped powder composition NaNbO ₃ And wet-mixing with a ZrO ₂ ball for 20 hours using an organic solvent as a medium, followed by calcination and wet grinding in the same manner as in Example 1 to obtain an average particle size of about 0.5 μm. A calcined powder (fine powder) was obtained.

Next, the anisotropically shaped powder and the fine powder were mixed in the same manner as in Example 1 to obtain a slurry-like raw material mixture (mixing step).
Further, in the same manner as in Example 1, the raw material mixture was formed into a tape shape, and the formed body was laminated, pressed and rolled to obtain a plate-like formed body having a thickness of 1.5 mm. This molded body was degreased and CIP treated, and then fired in the same manner as in Example 1 to obtain a crystallographically oriented ceramic. This is designated as Sample C1.

  With respect to the obtained crystallographically-oriented ceramic (sample C1), the orientation degree of the {100} plane (average orientation degree F (100)) was measured in the same manner as in Example 1. As a result, the average degree of orientation of sample C1 was 85%.

When crystal oriented ceramics are produced using NaNbO ₃ powder as anisotropically shaped powder as in this example, crystal oriented ceramics with a high degree of orientation can be produced.
However, oriented particles composed of NaNbO ₃ are complicated to synthesize, and Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder that easily forms an oriented surface is synthesized at one end, and this Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder is used. Need to be manufactured. Therefore, the manufacturing process becomes complicated, the productivity is lowered, and the manufacturing cost is increased.

Explanatory drawing which shows the structure of the conventional slurry formed by mixing plate-shaped powder and raw material powder. Explanatory drawing which shows the structure of a slurry. Explanatory drawing which shows the conventional molded object which is a molded object which has plate-shaped powder and raw material powder, and plate-shaped powder was orientated to the fixed direction inside. Explanatory drawing which shows a mode that anisotropic shaped powder grows in the molded object during sintering. Explanatory drawing which shows the structure of crystal orientation ceramics.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anisotropic shape powder 2 Fine powder 3 Raw material mixture 4 Solvent 5 Molded body 8 Crystal orientation ceramics

Claims (6)

An anisotropic shaped powder used as a template for producing a crystal oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase and having a pseudo cubic {100} plane constituting the polycrystal. There,
The anisotropically shaped powder is composed of anisotropically oriented particles whose {010} plane is developed to form an oriented surface,
The oriented particle is a layered compound represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ (however, in the general formulas (1) and (2), the A site element is at least K). And a B-site element containing at least Nb as a main component). The anisotropically shaped powder according to claim 1, wherein the layered compound is K ₄ Nb ₆ O ₁₇ or KNb ₃ O ₈ . 3. The isotropic perovskite compound according to claim 1, wherein the isotropic perovskite compound has the general formula (3): {Li _x (K _1−y Na _y ) _1−x } _a (Nb _1−zw Ta _z Sb _w ) O ₃ (However, 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0, 0.95 ≦ a ≦ 1.05) An anisotropically shaped powder characterized by In a method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, the pseudo-cubic {100} plane constituting the polycrystal is oriented,
A layered compound represented by the general formula (1) A ₄ B ₆ O ₁₇ or the general formula (2) AB ₃ O ₈ (however, in the general formulas (1) and (2), the A site element contains at least K as a main component, B-site element is composed of at least Nb as a main component), and an anisotropically shaped powder comprising anisotropically oriented particles whose {010} plane develops to form an oriented surface; A mixing step of obtaining a raw material mixture by mixing fine powders having an average particle size of 3 or less and forming the isotropic perovskite compound by sintering together with the anisotropically shaped powder;
A molding step of molding the raw material mixture to obtain a molded body so that the oriented surfaces of the anisotropically shaped powder are oriented in substantially the same direction; and
A method for producing a crystallographically-oriented ceramic, comprising: a step of heating the shaped body and sintering the anisotropically shaped powder and the fine powder to obtain the crystallographically-oriented ceramic. 5. The method for producing a crystallographically-oriented ceramic according to claim 4, wherein the layered compound is K ₄ Nb ₆ O ₁₇ or KNb ₃ O ₈ . According to claim 4 or 5, the isotropic perovskite type compound represented by the general formula _{(3): {Li x (} K 1-y Na y) 1-x} a (Nb 1-zw Ta z Sb w) O 3 (However, 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0, 0.95 ≦ a ≦ 1.05) A method for producing a crystallographically-oriented ceramic, characterized by being used for producing the above-mentioned crystallographically-oriented ceramic.

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