JP2009242168A - Method for manufacturing crystal-oriented ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing crystal-oriented ceramics, in which the orientational degree of each of the crystal-oriented ceramics can be improved. <P>SOLUTION: The method for manufacturing crystal-oriented ceramics includes a mixing step, a molding step and a firing step. At the mixing step, anisotropic powder is mixed with reactive raw material powder, which is reacted with the anisotropic powder to produce an isotropic perovskite-type compound, to obtain a raw material mixture. At the molding step, the obtained raw material mixture is molded so that the crystal surfaces of the anisotropic powder are oriented to almost the same direction to obtain a molding. At the firing step, the obtained molding is heated to obtain the crystal-oriented ceramics. At the mixing step, the anisotropic powder is mixed with the reactive raw material powder at such a stoichiometric ratio that the isotropic perovskite-type compound shown by general formula (1): äLi<SB>x</SB>(K<SB>1-y</SB>Na<SB>y</SB>)<SB>1-x</SB>}<SB>a</SB>(Nb<SB>1-z-w</SB>Ta<SB>z</SB>Sb<SB>w</SB>)O<SB>3</SB>is produced, and Nb<SB>2</SB>O<SB>5</SB>powder of 0.005-0.02 moles is mixed in 1 mole isotropic perovskite-type compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

In recent years, piezoelectric materials and dielectric materials have been demanded that do not contain lead, which is an environmentally hazardous substance, and have good piezoelectric characteristics and dielectric characteristics. As a candidate for such a material, (Li, K, Na) (Nb, Ta, Sb) O ₃ -based crystallographic ceramics are considered promising.

Specifically, for example, the general formula _{{Li x (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) has been developed (see Patent Document 1). A plate-like powder made of NaNbO ₃ has been used for the production of this crystal oriented ceramic. Specifically, a mixture obtained by mixing the plate-like powder and the reaction raw material is formed into a sheet, and a plurality of the obtained sheets are laminated to produce a laminated body. Thereafter, the laminated body is rolled, degreased, and statically treated. A crystallographically-oriented ceramic can be produced by performing a water pressure (CIP) treatment and heating in oxygen (see Patent Document 1). Such a crystallographically-oriented ceramic can have a high density and a relatively high degree of orientation.

  However, the degree of orientation of crystal-oriented ceramics produced by such a conventional production method has not yet been sufficient. That is, in order to obtain high piezoelectric properties and dielectric properties comparable to lead-based piezoelectric materials and dielectric materials with non-lead-based materials, it has been desired to develop crystal-oriented ceramics with a higher degree of orientation.

JP 2004-300019 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a method for producing a crystallographically-oriented ceramic that can improve the degree of orientation of the crystallographically-oriented ceramic.

The present invention is a method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, wherein the crystal plane {100} plane of crystal grains constituting the polycrystal is oriented,
Mixing an anisotropically shaped powder composed of anisotropically oriented particles having a crystal plane {100} plane oriented and a reaction raw material powder that reacts with the anisotropically shaped powder to produce the isotropic perovskite compound. A mixing step of preparing a raw material mixture by:
A molding step of molding the raw material mixture to produce a molded body such that the crystal plane {100} plane of the anisotropically shaped powder is oriented in substantially the same direction;
A heating step of reacting and sintering the anisotropically shaped powder and the reaction raw material powder by heating the molded body to obtain the crystal-oriented ceramics,
In the mixing step, the general formula (1) {Li _x (K _{1 -y} Na _y ) _1-x } _a (Nb _{1 -zw} Ta _z ) is obtained from the anisotropic shaped powder and the reaction raw material powder after the firing step. 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) The anisotropically shaped powder and the reaction raw material powder are mixed at a stoichiometric ratio that produces the isotropic perovskite compound represented by (05), and the above-described general formula (1) is further mixed. Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder are mixed so that the amount added per mole of isotropic perovskite compound is 0.005 to 0.02 mol. (Claim 1).

In the production method of the present invention, the crystallographically-oriented ceramic is produced by performing the mixing step, the forming step, the evaluation step, and the firing step. The most notable point in the present invention is that, in the mixing step, Nb is further added so that the addition amount with respect to 1 mol of the isotropic perovskite compound represented by the general formula (1) is 0.005 to 0.02 mol. ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added.
As described above, when the forming step and the firing step are performed using the raw material mixture to which the predetermined amount of Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added, Nb ₂ O ₅ powder or Ta ₂ O Compared to the case where ₅ powders are not added, the above-mentioned crystallographically-oriented ceramic having a higher degree of orientation can be produced.

The reason is presumed as follows.
Formation of the above-mentioned crystallographically-oriented ceramics occurs when crystal-oriented particles are formed and sintered as a result of the anisotropically shaped powder reacting and sintering with surrounding reaction raw materials in the firing process. The crystal-oriented ceramic is sintered at a higher temperature than the solid phase line. That is, the reaction raw material is in a semi-molten state (mixed state of liquid phase and solid phase) during sintering. At this time, if the amount of the liquid phase is large, it is considered that the arrangement of the anisotropically shaped powder is disturbed by the driving force of sintering, and the crystal orientation degree of the sintered body is lowered.
Therefore, the present inventors paid attention to the fact that the degree of crystal orientation can be improved by reducing the amount of the liquid phase.

That is, since the liquid phase contains an alkali metal element, it is noted that the amount of the liquid phase can be reduced by adding an element that reacts and solidifies with the alkali metal element. Specifically, Nb ₂ O ₅ and / or It has been found that the amount of liquid phase can be reduced by adding Ta ₂ O ₅ . Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder has a function of directly reacting with the liquid phase generated during the sintering process to reduce the amount of the liquid phase.
In particular, since Nb is a main elemental component in the general formula (1), even if Nb ₂ O ₅ powder is added, the change in the composition ratio due to the addition can be further reduced.

Further, when Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added, the ratio (A / B) between the A site and the B site of the perovskite type compound (ABO ₃ ) changes. Therefore, it is considered that the effect of improving the degree of crystal orientation by the Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is caused by the change in the A / B ratio due to the addition, but also shown in the examples described later. Thus, even if Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added so that A / B does not change, the effect of improving the degree of orientation occurs. Therefore, it is considered that the effect of improving the degree of orientation is the effect of adding Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder itself.

Further, even if Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added in the above amount, there is not much influence on the sinterability in the firing step, and crystal oriented ceramics can be produced without substantially reducing the density. it can.
In the present invention, the above-mentioned crystallographically-oriented ceramic with {100} planes oriented can be produced. Such crystal oriented ceramics can exhibit excellent piezoelectric properties such as piezoelectric d constant. Therefore, it is suitable as a piezoelectric material such as a piezoelectric element.

  As described above, according to the present invention, it is possible to provide a method for producing a crystallographically-oriented ceramic that can improve the degree of orientation of the crystallographically-oriented ceramic.

Next, a preferred embodiment of the present invention will be described.
In the present 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 crystal plane of the crystal grains constituting the polycrystal The above-mentioned crystallographically-oriented ceramic in which the {100} plane is oriented is produced.
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.
“The crystal plane {100} plane is oriented” means that the crystal grains are arranged so that the {100} planes of the perovskite type compound are parallel to each other (hereinafter, this state is appropriately referred to as “ "Plane orientation").

“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 ΣI ₀ (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 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.

In the mixing step, the raw material mixture is prepared by mixing the anisotropically shaped powder, the reaction raw material powder, Nb ₂ O ₅ powder and / or Ta ₂ O ₅ .

In the present invention, the “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.
As the oriented particles, it is preferable to use particles having a shape that can be easily oriented in a certain direction during the molding step. 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.

  In the firing step, the anisotropically shaped powder and the reaction raw material powder react and sinter to form crystal particles. Therefore, 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.

In the mixing step, the anisotropically shaped powder and the reaction raw material powder are represented by the general formula (1) {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -zw} Ta _z ) in the firing step. 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) and is mixed at a stoichiometric ratio that produces the above isotropic perovskite type compound.
In the general formula (1), “x + z + w> 0” indicates that at least one of Li, Ta, and Sb may be included as a substitution element.

Further, when the compound represented by the general formula (1) is applied to the composition formula ABO ₃ of the 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 above general formula, 0.95 ≦ a ≦ 1.05, and preferably 0.97 ≦ a ≦ 1.03.
The actual isotropic perovskite type compound (ABO ₃ ) after adding the Nb ₂ O ₅ powder and / or the Ta ₂ O ₅ powder in addition to the anisotropically shaped powder and the reaction raw material powder and calcining. In the composition, the ratio A / B of the A site element to the B site element is preferably 0.94 to 1. If it is less than 0.94, a heterogeneous phase may occur and the degree of orientation may decrease. On the other hand, if it exceeds 1, the alkali metal component may segregate at the crystal grain boundaries and the insulation resistance may decrease. Also from this viewpoint, in the mixing step, as described above, a in the general formula (1) is 0.95 ≦ a ≦ 1.05, more preferably 0.97 ≦ a ≦ 1.03. It is preferable to mix the anisotropically shaped powder and the reaction raw material powder.

In the general formula (1), “y” represents the ratio of K and Na contained in the isotropic perovskite compound. In the compound represented by the general formula (1), 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 (1) 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 characteristics such as the piezoelectric g ₃₁ constant of the crystal-oriented ceramic can be improved.
The range of y in the general formula (1) can be 0 ≦ y <1.
In this case, K is an essential component in the compound represented by the general formula (1). Therefore, in this case, the piezoelectric characteristics such as the piezoelectric d ₃₁ constant of the crystal-oriented ceramic can be 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 (1), 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. Therefore, the crystal oriented ceramic is more suitable as a piezoelectric material. 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 (1) is more preferably 0 <x ≦ 0.2.
In this case, in the compound represented by the general formula (1), Li is an essential component. Therefore, the crystallographically-oriented ceramic can be more 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 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 (1) can be set to x = 0.
In this case, the general formula (1) is represented by _{(K 1-y Na y)} a (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 (1), 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 (1), if the value of z exceeds 0.4, the Curie temperature is lowered, and there is a possibility that it may be difficult to use it as a piezoelectric material for home appliances or automobiles.
The range of z in the general formula (1) 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.

In addition, the value of z in the general formula (1) can be set to z = 0.
In this case, the general formula (1) is represented by {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -w} Sb _w ) O ₃ . In this case, the compound represented by the general formula (1) does not contain Ta. Therefore, in this case, the compound represented by the general formula (1) can exhibit excellent piezoelectric characteristics without using an expensive Ta component at the time of production.
In the general formula (1), 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 (1) is 0 <w <= 0.2.
In this case, Sb is an essential component in the compound represented by the general formula (1). 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.

Moreover, the value of w in the general formula (1) can be set to w = 0. In this case, the general formula (1) is represented by {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (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 (1), the value of w is more preferably 0 ≦ w ≦ 0.15, and further preferably 0 ≦ w ≦ 0.10.

  In the above-mentioned crystallographically-oriented ceramic, the crystal phase changes from cubic to tetragonal (first crystal phase transition temperature = Curie temperature) and tetragonal to orthorhombic (second crystal phase transition temperature as the temperature changes from high to low. ), Rhombohedral to rhombohedral (third crystal phase transition temperature). In the temperature region higher than the first crystal phase transition temperature, the displacement characteristic disappears because it becomes a cubic crystal, and in the temperature region lower than the second crystal phase transition temperature, it becomes an orthorhombic crystal. The temperature dependence of the capacity increases. Therefore, it is desirable that the first crystal phase transition temperature is higher than the use temperature range, and the second crystal phase transition temperature is lower than the use temperature range so that the first crystal phase transition temperature is tetragonal over the entire use temperature range.

However, potassium sodium niobate (K _1-y Na _y NbO ₃ ), which is the basic composition of the above-mentioned crystal orientation ceramics, is the “Journal of American Ceramic Society”, USA, 1959. 42 [9] p. According to 438-442 and U.S. Pat. No. 2,976,246, the crystal phase is changed from cubic to tetragonal (first crystal phase transition temperature = Curie temperature), tetragonal to orthorhombic ( (Second crystal phase transition temperature), rhombic crystal → rhombohedral crystal (third crystal phase transition temperature). The first crystal phase transition temperature at “y = 0.5” is about 420 ° C., the second crystal phase transition temperature is about 190 ° C., and the third crystal phase transition temperature is about −150 ° C. Accordingly, the temperature range of tetragonal crystal is in the range of 190 to 420 ° C., which does not coincide with −40 to 160 ° C., which is a general industrial product use temperature range.
On the other hand, the above-mentioned crystallographic ceramics can be obtained by changing the amounts of Li, Ta, and Sb substitution elements with respect to potassium sodium niobate (K _1-y Na _y NbO ₃ ), which is the basic composition. The phase transition temperature as well as the second crystal phase transition temperature can be freely changed.

The following formulas B1 and B2 show the results of multiple regression analysis of the substitution amounts of Li, Ta, and Sb and the actual measured values of the crystal phase transition temperature at y = 0.4 to 0.6 at which the piezoelectric characteristics become the largest. .
From formulas B1 and B2, it can be seen that the amount of Li substitution has the effect of increasing the first crystal phase transition temperature and decreasing the second crystal phase transition temperature. It can also be seen that Ta and Sb have the effect of lowering the first crystal phase transition temperature and lowering the second crystal phase transition temperature.
First crystal phase transition temperature = (388 + 9x−5z−17w) ± 50 [° C.] (formula B1)
Second crystal phase transition temperature = (190-18.9x-3.9z-5.8w) ± 50 [° C.] (formula B2)

  The first crystal phase transition temperature is a temperature at which the piezoelectricity completely disappears, and the dynamic capacity rapidly increases in the vicinity thereof. Therefore, the first crystal phase transition temperature is desirably (product use environment upper limit temperature + 60 ° C.) or higher. The second crystal phase transition temperature is simply the temperature at which the crystal phase transition occurs, and since the piezoelectricity does not disappear, it may be set within a range that does not adversely affect the temperature dependence of displacement or dynamic capacity. Environmental lower limit temperature + 40 ° C.) or less is desirable.

  On the other hand, the use environment upper limit temperature of a product changes with uses, and is 60 degreeC, 80 degreeC, 100 degreeC, 120 degreeC, 140 degreeC, 160 degreeC, etc. The use environment minimum temperature of a product is -30 degreeC, -40 degreeC, etc.

Therefore, since the first crystal phase transition temperature shown in the above formula B1 is desirably 120 ° C. or higher, it is desirable that “x”, “z”, and “w” satisfy (388 + 9x−5z−17w) + 50 ≧ 120. .
In addition, since the second crystal phase transition temperature represented by Formula B2 is desirably 10 ° C. or lower, “x”, “z”, and “w” are (190-18.9x-3.9z-5.8w) − It is desirable to satisfy 50 ≦ 10.
That is, it is preferable that the general formula (1) satisfies the relations 9x-5z-17w ≧ −318 and −18.9x−3.9z−5.8w ≦ −130.

Next, as the anisotropically shaped powder, the general formula (2) (Bi ₂ O ₂ ) ²⁺ {Bi _0.5 (K _u Na _1-u ) _m-1.5 (Nb _1-v Ta _v ) _m O _{3m + 1} } ^2- (where m is an integer of 2 or more, 0 ≦ u ≦ 0.8, 0 ≦ v ≦ 0.4) acid treatment of an anisotropically shaped starting material composed of a bismuth layered perovskite compound It is preferable to employ an acid-treated product obtained by doing this (claim 2).
In this case, the degree of orientation can be improved while further suppressing the decrease in density. That is, if the amount of liquid phase is reduced by adding Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder, the degree of orientation of the crystal-oriented ceramic can be improved, but the crystal-oriented ceramic may be difficult to sinter. The acid-treated body has many A-site defects (alkali metal element defects) and is excellent in reactivity with a liquid phase containing an alkali metal element derived from a reaction raw material at the time of sintering, so that the sinterability can be improved. it can.

For example, in the case of producing a crystallographically-oriented ceramic using a plate-like powder made of NaNbO ₃ or the like as an anisotropically shaped powder, the surface of the plate-like powder has a rough property, so that the orientation of the plate-like powder during molding is May decrease. On the other hand, when the acid-treated product is the anisotropically shaped powder, the surface of the plate-like powder is smooth, so that the orientation during molding can be improved. Therefore, a crystallographically-oriented ceramic with a higher degree of orientation can be obtained.

  When the value of u in the general formula (2) exceeds 0.8, the melting point of the anisotropically shaped powder is lowered, and when crystal oriented ceramics are produced using the anisotropically shaped powder, It may be difficult to obtain oriented ceramics. On the other hand, when v exceeds 0.4, when crystal oriented ceramics are produced using the anisotropically shaped powder, the Curie temperature of the obtained crystal oriented ceramics decreases, and piezoelectric materials for home appliances and automobiles, etc. May be difficult to use. On the other hand, if m is too large, non-anisotropically shaped fine particles of perovskite may be generated in addition to the anisotropically shaped powder of the bismuth layered perovskite type compound. Therefore, m is preferably an integer of 15 or less from the viewpoint of improving the yield of anisotropically shaped particles.

The acid treatment can be performed by bringing the starting material into contact with an acid such as hydrochloric acid.
Specifically, for example, a method of mixing starting material powder while heating in an acid can be employed.

  Further, as the reaction raw material powder, a powder that reacts with the anisotropically shaped powder by sintering together with the anisotropically shaped powder to produce a desired isotropic perovskite type compound is selected.

The reaction raw material powder preferably has a particle size of 1/3 or less of the anisotropically shaped powder.
When the particle size of the reaction raw material powder exceeds 1/3 of the particle size of the anisotropically shaped powder, the {100} plane of the anisotropically shaped powder is oriented in substantially the same direction in the molding step. Thus, 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 reaction raw material powder and the anisotropic shaped powder can be compared by comparing the average particle size of the reaction raw material powder with the average particle size of the anisotropic shaped powder. The particle diameter of the anisotropically shaped powder and the particle diameter of the reaction raw material powder both mean the longest diameter.

  The composition of the reaction raw material 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 (1) to be produced. Further, as the reaction raw material powder, for example, an oxide powder, a composite oxide powder, a hydroxide powder, a salt such as carbonate, nitrate, main acid salt, or an alkoxide can be used.

  As said reaction raw material powder, 1 or more types of calcined powder chosen 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.

Further, as the reaction raw material powders, the general formula _{(3) {Li p (K} 1-q Na q) 1-p} c (Nb 1-rs Ta r Sb s) O 3 ( where, 0 ≦ p ≦ 1 , 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, 0 ≦ s ≦ 1, 0.95 ≦ c ≦ 1.05) is preferably employed (preferably a powder composed of an isotropic perovskite type compound). Item 3).
In this case, it is possible to easily produce a high-density and highly oriented crystal-oriented ceramic.

Also in the above general formula (3), when this is applied to the compositional formula ABO ₃ of the perovskite structure, the composition ratio of the A site atom and the B site atom shifted to ± 5% with respect to 1: 1, respectively. It can be. 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 ≦ c ≦ 1.05 is preferable, and 0.97 ≦ c ≦ 1.03 is more preferable.
Similarly to the general formula (1), the general formula (3) also satisfies the relations of 9p-5q-17s ≧ −318 and −18.9p−3.9r−5.8s ≦ −130. It is preferable.

In the mixing step, the anisotropic shaped powder and the reaction raw material powder are blended in a stoichiometric ratio represented by the general formula (1). At this time, the blending ratio of the anisotropically shaped powder and the reaction raw material powder is a molar ratio, anisotropically shaped powder: reactive raw material powder = 0.02 to 0.10: 0.98 to 0.90 (however, The total of the anisotropically shaped powder and the reaction raw material is preferably 1 mol).
In the above blending ratio (molar ratio), when the anisotropically shaped powder is less than 0.02 or when the reaction raw material powder exceeds 0.98, Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added. Although the effect of improving the degree of orientation can be obtained, it may be difficult to increase the degree of orientation to a practically sufficient level for applications such as piezoelectric materials.
On the other hand, when the anisotropically shaped powder exceeds 0.10 or when the reaction raw material 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.

Further, in the mixing step, so that the amount added to said isotropic perovskite compound 1mol represented by the general formula (1) is 0.005~0.02mol, Nb ₂ O ₅ powder and / or Mix Ta ₂ O ₅ powder. When both Nb ₂ O ₅ powder and Ta ₂ O ₅ powder are used, the sum of these is 0.005 to 0.005 with respect to 1 mol of the isotropic perovskite compound represented by the general formula (1). It can add so that it may become 02 mol.
When the addition amount of Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is less than 0.005 mol, the above-mentioned degree of orientation can be increased by adding Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder. There is a possibility that the improvement effect cannot be obtained sufficiently. On the other hand, if it exceeds 0.02 mol, the degree of orientation may rather be reduced. More preferably, the addition amount of Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is 0.015 mol or less with respect to 1 mol of the isotropic perovskite compound represented by the general formula (1). Good.

Nb ₂ O ₅ powder and Ta ₂ O ₅ powder can constitute a part of the component elements of the isotropic perovskite compound after firing. Therefore, the composition of the crystallographically-oriented ceramic after the firing step is actually the Nb ₂ O ₅ powder and / or the Ta ₂ O from the target composition from the anisotropic shaped powder and the reaction raw material powder in the mixing step. _It is thought that it is shifted by the added amount of ₅ powders. In the present invention, the composition represented by the general formula (1) in the mixing step includes the anisotropic shaped powder not considering the addition of Nb ₂ O ₅ powder and Ta ₂ O ₅ powder, and the reaction raw material powder. In the mixing step, a predetermined amount of Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder is added as described above with respect to 1 mol of the composition.

Preferably, in the mixing step, it is preferable to add Nb ₂ O ₅ powder out of Nb ₂ O ₅ powder and Ta ₂ O ₅ powder.
In this case, the ratio of the composition change of the perovskite type compound due to the addition of Nb ₂ O ₅ powder can be reduced.

In the mixing step, the anisotropically shaped powder, the reaction raw material, the Nb ₂ O ₅ powder, and the Ta ₂ O ₅ powder may be mixed 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, one or more selected from a binder, a plasticizer, a dispersant, and the like can be added as necessary.

Next, in the molding step, the raw material mixture is molded so that the crystal plane {100} of the anisotropically shaped powder is oriented in substantially the same direction, thereby producing a molded body.
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 reaction raw material are reacted and sintered to obtain the crystal oriented ceramics. In the firing step, the compact is heated by heating the compact, and the crystal-oriented ceramic composed of a polycrystalline body having the isotropic perovskite compound as a main phase is produced. In the firing step, an excess component is also generated at the same time depending on the composition of the anisotropically shaped powder and the reaction raw material.

  The heating temperature in the firing step is an anisotropic powder to be used, a reaction raw material, 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 comprises a polycrystal having an isotropic perovskite compound as a main phase by performing a mixing step, a forming step, and a firing step, and the crystal plane {100} plane of the crystal grains constituting the polycrystal This is an example of producing a crystallographically-oriented ceramic in which is oriented.

In the mixing step, an anisotropically shaped powder comprising anisotropically oriented particles whose crystal plane {100} plane is oriented, and a reaction raw material powder that reacts with this anisotropically shaped powder to produce an isotropic perovskite type compound, To prepare a raw material mixture. Further, in the mixing step, after the post-baking step, the anisotropic shaped powder and the reaction raw material powder are represented by {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _1.020 (Nb _0.84 Ta _0.099 Sb _0.061 ) O _3. The anisotropic shaped powder and the reaction raw material powder are mixed at a stoichiometric ratio that produces the isotropic perovskite compound, and the addition amount with respect to 1 mol of the isotropic perovskite compound is 0.005 to 0.02 mol. Nb ₂ O ₅ powder is mixed.

In the forming step, the raw material mixture is formed so that the crystal plane {100} plane of the anisotropically shaped powder is oriented in substantially the same direction to produce a formed body.
In the firing step, by heating the compact, the anisotropically shaped powder and the reaction raw material powder are reacted and sintered to obtain crystal oriented ceramics.

Hereinafter, the manufacturing method of the crystallographically-oriented ceramic of this example will be described in detail.
First, an anisotropic shaped powder is produced. In this example, Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ (ie, (Bi ₂ O ₂ ) ²⁺ {(Bi _0.5 Na _3.5 ) (Nb _0.93 Ta _0.07 ) ₅ O is used as the anisotropically shaped powder. ₁₆ } Use an acid-treated product obtained by acid-treating an anisotropic starting material composed of a bismuth layered perovskite type compound represented by ^2- ).

That is, first, Bi ₂ O ₃ powder, NaHCO ₃ powder, Nb ₂ O ₅ powder, and Ta ₂ O ₅ powder with a stoichiometric ratio of Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ are used. Weighed and wet mixed. Next, 80 parts by weight of NaCl as a flux was added to 100 parts by weight of the obtained mixture, and dry mixed for 1 hour.
Next, the obtained mixture was heated in a platinum crucible at a temperature of 1100 ° C. for 2 hours to synthesize Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ . Heating was performed from room temperature to a temperature of 850 ° C. at a heating rate of 150 ° C./h, and from 850 ° C. to 1100 ° C. at a heating rate of 100 ° C./h. Then cooled at a cooling rate 0.99 ° C. / h, the reaction was removed flux hot water washing to obtain a _{Bi 2.5 Na 3.5 (Nb 0.93 Ta} 0.07) 5 O 18 powder. This Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) 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 _0.93 Ta _0.07 ) ₅ O ₁₈ powder was pulverized by a jet mill.
The Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ powder after pulverization had an average particle size of about 12 μm and an aspect ratio of about 10 to 20 μm.

Then, 6N HCl was added at a rate of 30 ml to 1 g of this starting material powder (Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ powder) in a beaker, and the mixture was stirred at a temperature of 60 ° C. for 24 hours. Thereafter, suction filtration was performed. This acid washing step was repeated twice to obtain an acid-treated product of Bi _2.5 Na _3.5 (Nb _0.93 Ta _0.07 ) ₅ O ₁₈ powder.

As a result of component analysis using an energy dispersive X-ray apparatus (EDX) and identification of a crystal phase using an X-ray diffractometer (XRD), the anisotropic shaped powder is Na _0.5 ( Nb _0.93 Ta _0.07 ) O ₃ powder was found as the main component, and it was found that this structure had both a structure composed of a perovskite compound and a structure composed of a bismuth layered compound. This anisotropically shaped powder was a plate-like powder having an average particle size of about 12 μm and an aspect ratio of about 10 to 20 μm.

Next, a reaction raw material powder was produced as follows.
First, from 1 mol of {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _1.020 (Nb _0.84 Ta _0.099 Sb _0.061 ) O ₃ , Na _0.5 (Nb _0.93 Ta _0.07 ) O ₃ 0.05 mol used as anisotropically shaped powder The commercially available NaHCO ₃ powder, KHCO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and NaSbO ₃ powder were weighed so as to obtain a composition obtained by subtracting.
Specifically, it was weighed so as to have a stoichiometric composition of {Li _0.06 (K _0.45 Na _0.55 ) _0.94 } _1.047 (Nb _0.835 Ta _0.1 Sb _0.065 ) O ₃ .
Thereafter, wet mixing was performed for 20 hours with a ZrO ₂ ball using an organic solvent as a medium. Next, calcined for 5 hours at 750 ° C., and further wet pulverized for 20 hours with a ZrO ₂ ball using an organic solvent as a medium to obtain a calcined powder (reaction raw material powder) having an average particle size of about 0.5 μm. .

The anisotropically shaped powder and the reaction raw material powder produced as described above are weighed in a stoichiometric ratio such that {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _1.020 (Nb _0.84 Ta _0.099 Sb _0.061 ) O _3. Further, Nb ₂ O ₅ powder as an additive was added to obtain a raw material mixture (mixing step). Specifically, the anisotropic shaped powder and the reaction raw material powder are weighed so as to have a molar ratio of 0.05: 0.95 (anisotropic shaped powder: reactive raw material powder), and further Nb ₂ O as an additive. ₅ powder 0.01 mol was added.
After weighing, a raw material mixture slurry was obtained by performing wet mixing with a ZrO ₂ ball for 20 hours using an organic solvent as a medium. Thereafter, a binder (polyvinyl butyral) and a plasticizer (dibutyl phthalate) were added to the slurry and further mixed. The binder and plasticizer were added in an amount of 8.0 g (binder) and 4.0 g (plasticizer) to 100 g of the raw material mixture (powder component), respectively. In this way, a slurry-like raw material mixture was obtained.

  Next, using a doctor blade device, the mixed slurry-like raw material mixture is formed into a tape having a thickness of 100 μm, and the resulting tape is laminated and pressure-bonded, whereby a laminated body having a thickness of 1.2 mm is formed. (Molding process). At this time, the anisotropically shaped powder can be oriented in substantially the same direction in the molded body due to shear stress acting on the anisotropically shaped powder.

  Next, the molded body was degreased by heating in the atmosphere at a temperature of 400 ° C. The degreased compact was placed on a Pt plate in a magnesia pot, fired by heating in the atmosphere at a temperature of 1120 ° C. for 2 hours, and then cooled to obtain crystal-oriented ceramics (firing step). This is designated as Sample E1. Heating and cooling were performed at a heating rate of 200 ° C./h, a cooling rate of 10 ° C./h between 1120 ° C. and 1000 ° C., and a heating rate of 1000 ° C. or lower was 200 ° C./h.

The composition of the obtained crystallographically-oriented ceramic (sample E1) is finally {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } from the composition and blending ratio of the anisotropic shaped powder, the reaction raw material powder, and the Nb ₂ O ₅ powder. Nb _0.843 Ta _0.097 Sb _0.06 ) O ₃ .
Composition of anisotropic shaped powder and reaction raw material powder used for preparation of sample E1, addition amount of Nb ₂ O ₅ powder, target composition at the time of mixing anisotropic shaped powder and reaction raw material powder in mixing step, after firing The composition of the perovskite type compound is shown in Table 1 below.

Further, the bulk density of the crystal oriented ceramic of the sample E1 was measured.
Specifically, first, the weight (dry weight) at the time of drying of the crystal oriented ceramics was measured. Next, the crystallographically-oriented ceramic was immersed in water to allow water to penetrate into the opening, and then the weight of the crystal-oriented ceramic (water content) was measured. Next, the volume of open pores present in the crystal-oriented ceramic was calculated from the difference between the moisture content and the dry weight. Further, the volume of the portion excluding the open pores was measured for the crystallographically-oriented ceramic by the Archimedes method. Next, the bulk density of the crystal-oriented ceramics was calculated by dividing the dry weight of the crystal-oriented ceramics by the total volume (the sum of the volume of open pores and the volume of the portion excluding the open pores). The results are shown in Table 1 below.

Moreover, the degree of orientation inside the crystal-oriented ceramic of the sample E1 was measured.
Specifically, first, a surface parallel to the tape surface was polished from the surface to a depth of 150 μm. With respect to this polished surface, the average orientation degree F (100) of {100} planes by the Lotgering method was calculated using the above equation (1). The results are shown in Table 1 below.

Further, in this example, as a comparison with the sample E1, the crystal-oriented ceramic (sample C1) is obtained by performing a mixing step without adding the Nb ₂ O ₅ powder when mixing the anisotropic shaped powder and the reaction raw material powder. Produced. In the preparation of the sample C1, the reaction raw material composition was changed from the case of E1 so that the A-site / B-site ratio of the finally obtained crystal-oriented ceramic was the same as the sample E1 (A site / B site = 1). changed.

That is, in producing the sample C1, first, an anisotropic shaped powder was produced in the same manner as in the case of the sample E1.
Further, commercially available NaHCO ₃ powder, KHCO ₃ powder, Li ₂ CO ₃ powder, so as to have a stoichiometric composition of {Li _0.06 (K _0.45 Na _0.55 ) _0.94 } _1.026 (Nb _0.835 Ta _0.1 Sb _0.065 ) O ₃ , Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and NaSbO ₃ powder were weighed. Thereafter, as in the case of the sample E1, wet mixing was performed for 20 hours with a ZrO ₂ ball using an organic solvent as a medium. Next, calcined for 5 hours at 750 ° C., and further wet pulverized for 20 hours with a ZrO ₂ ball using an organic solvent as a medium to obtain a calcined powder (reaction raw material powder) having an average particle size of about 0.5 μm. .

Subsequently, similarly to the sample E1, the anisotropically shaped powder and the reaction raw material powder were weighed so that the molar ratio was 0.05: 0.95 (anisotropically shaped powder: reactive raw material powder).
After weighing, in the same manner as the sample E1, wet mixing was performed using an organic solvent as a medium, and a binder and a plasticizer were added and further mixed to obtain a slurry-like raw material mixture.

Further, in the same manner as the sample E1, the raw material mixture is formed into a tape shape, and further laminated and pressed to produce a laminated body having a thickness of 1.2 mm, and then degreased and fired. A crystallographically oriented ceramic was obtained. This is designated as Sample C1.
Composition of anisotropic shaped powder and reaction raw material powder used for preparation of sample C1, addition amount of Nb ₂ O ₅ powder, target composition at the time of mixing anisotropic shaped powder and reaction raw material powder in mixing process, perovskite after firing The composition of the mold compound is shown in Table 1 below.
For sample C1, the composition after firing, the bulk density, and the average degree of orientation were measured in the same manner as in sample E1. The results are shown in Table 1.

As is known from Table 1, sample E1 prepared by adding Nb ₂ O ₅ powder in addition to the anisotropically shaped powder and reaction raw material powder in the mixing step is sample C1 prepared without using Nb ₂ O ₅ powder. The degree of orientation is improved compared to. Moreover, each sample showed a comparable density.
Therefore, it can be seen that by adding Nb ₂ O ₅ powder in the mixing step, the degree of orientation of the crystal-oriented ceramic can be improved without reducing the density.
In the present example, Nb ₂ O ₅ powder for the sample E1 and Nb ₂ O ₅ powder sample C1 not blended were blended, the ratio of the A site and the B site composition substantially the same are the same (A / B = 1) Crystal oriented ceramics were produced. Nevertheless, there was a difference in the degree of orientation between the two, and the degree of orientation of sample E1 blended with Nb ₂ O ₅ powder was improved as compared to sample C1 (see Table 1). Therefore, it improves the effect of the orientation degree by blending a Nb ₂ O ₅ powder, the ratio of the results A site and B site blended with this not due to the change, which is Nb ₂ O ₅ powder formulation It turns out that it is by itself.

(Example 2)
This example is an example in which a crystal-oriented ceramic is produced by mixing an anisotropically shaped powder and a reaction raw material powder with a composition different from those of the sample E1 and the sample C1 of Example 1. In this example, in the mixing step, the anisotropically shaped powder and the reaction raw material powder are mixed at a stoichiometric ratio of {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _0.975 (Nb _0.84 Ta _0.099 Sb _0.061 ) O _3. To do.
Specifically, first, an anisotropic shaped powder (Na _0.5 (Nb _0.93 Ta _0.07 ) O ₃ powder) was prepared in the same manner as in Example 1. Next, the composition of {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _0.975 (Nb _0.84 Ta _0.099 Sb _0.061 ) O ₃ is used as an anisotropically shaped powder, and the Na _0.5 (Nb _0.93 Ta _0.07 ) O ₃ powder 0.05 Commercially available NaHCO ₃ powder, KHCO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and NaSbO ₃ powder were weighed so as to obtain a composition with moles subtracted. Specifically, NaHCO ₃ powder, KHCO ₃ powder, Li ₂ CO ₃ powder, Nb so as to have a stoichiometric composition of {Li _0.06 (K _0.45 Na _0.55 ) _0.94 } (Nb _0.835 Ta _0.1 Sb _0.065 ) O _{3 2} O ₅ powder, Ta ₂ O ₅ powder, and NaSbO ₃ powder were weighed.
Thereafter, in the same manner as in Example 1, calcination and wet pulverization were performed to obtain a calcined powder (reaction raw material powder) having an average particle diameter of about 0.5 μm.

Next, the anisotropically shaped powder obtained as described above and the reaction raw material are chemically _converted into {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _0.975 (Nb _0.84 Ta _0.099 Sb _0.061 ) O _3. Weighed in a stoichiometric ratio, and Nb ₂ O ₅ powder as an additive was further added. Specifically, the anisotropically shaped powder and the reaction raw material are weighed so as to have a molar ratio of 0.05: 0.95 (anisotropically shaped powder: reactive raw material), and further Nb ₂ O ₅ powder as an additive 0.005 mol was added.

After weighing, in the same manner as in Example 1, wet mixing was performed using an organic solvent as a medium, and a binder and a plasticizer were added and further mixed to obtain a slurry-like raw material mixture.
Further, in the same manner as in Example 1, the raw material mixture was formed into a tape shape, and further laminated and pressure-bonded to produce a laminated body having a thickness of 1.2 mm, followed by degreasing and firing. A crystallographically oriented ceramic was obtained. This is designated as Sample E2.

The composition of the obtained crystallographically-oriented ceramic (sample E2) is finally {Li _0.059 (K _0.438 Na _0.562 ) _0.941 } _0.965 from the composition and blending ratio of the anisotropic shaped powder, the reaction raw material powder, and the Nb ₂ O ₅ powder. It is considered that (Nb _0.841 Ta _0.098 Sb _0.061 ) O ₃ .
Composition of anisotropic shaped powder and reaction raw material powder used for preparation of sample E2, amount of Nb ₂ O ₅ powder added, target composition at the time of mixing anisotropic shaped powder and reaction raw material powder in mixing step, after firing The composition of the perovskite type compound is shown in Table 2 below.

Further, in this example, four types of crystal-oriented ceramics with different addition amounts of Nb ₂ O ₅ powder added at the time of mixing the anisotropically shaped powder and the reaction raw material powder were prepared (sample E3). Sample E4, Sample C2, and Sample C3).
These were prepared in the same manner as Sample E2 except that the amount of Nb ₂ O ₅ powder added was different.
Composition of anisotropic shaped powder and reaction raw material powder used for preparation of each sample (sample E2 to sample E4, sample C2, and sample C3), addition amount of Nb ₂ O ₅ powder, anisotropic shaped powder and reaction in mixing step The target composition at the time of mixing with the raw material powder and the composition of the perovskite type compound after firing are shown in Table 2 below.
For each of these samples, the composition after firing, the bulk density, and the average degree of orientation were measured in the same manner as in Example 1. The results are shown in Table 2.

As is known from Table 2, even when crystal-oriented ceramics having a composition different from that of Example 1 is produced, Nb ₂ O ₅ powder is added in an amount of 0.005 to 0.005 mol when the anisotropically shaped powder and the reaction raw material powder are mixed. The crystal orientation ceramics (samples E2 to E4) added with 02 mol have an improved degree of orientation as compared with the sample C2 prepared without using the Nb ₂ O ₅ powder. Further, it showed a high density equivalent to or higher than that of the sample C2.
On the other hand, the crystal orientation ceramic (sample C3) produced by adding a relatively large amount (0.04 mol) of Nb ₂ O ₅ powder had rather a low degree of orientation.
Therefore, it can be seen that the amount of Nb ₂ O ₅ powder added is preferably 0.005 to 0.02 mol with respect to 1 mol of the isotropic perovskite compound. More preferably, 0.005-0.015 mol is good.

Claims (4)

A method for producing a crystallographically-oriented ceramic comprising a polycrystal having an isotropic perovskite type compound as a main phase, wherein a crystal plane {100} plane of crystal grains constituting the polycrystal is oriented,
Mixing an anisotropically shaped powder composed of anisotropically oriented particles having a crystal plane {100} plane oriented and a reaction raw material powder that reacts with the anisotropically shaped powder to produce the isotropic perovskite compound. A mixing step of preparing a raw material mixture by:
A molding step of molding the raw material mixture to produce a molded body such that the crystal plane {100} plane of the anisotropically shaped powder is oriented in substantially the same direction;
A heating step of reacting and sintering the anisotropically shaped powder and the reaction raw material powder by heating the molded body to obtain the crystal-oriented ceramics,
In the mixing step, the general formula (1) {Li _x (K _{1 -y} Na _y ) _1-x } _a (Nb _{1 -zw} Ta _z ) is obtained from the anisotropic shaped powder and the reaction raw material powder after the firing step. 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) The anisotropically shaped powder and the reaction raw material powder are mixed at a stoichiometric ratio that produces the isotropic perovskite compound represented by (05), and the above-described general formula (1) is further mixed. Nb ₂ O ₅ powder and / or Ta ₂ O ₅ powder are mixed so that the amount added per mole of isotropic perovskite compound is 0.005 to 0.02 mol. . According to claim 1, said as the anisotropically-shaped powder, the general formula _{(2) (Bi 2 O 2} ) 2+ {Bi 0.5 (K u Na 1-u) m-1.5 (Nb 1-v Ta v) m O _{3m + 1} } ²⁻ (where m is an integer of 2 or more, 0 ≦ u ≦ 0.8, 0 ≦ v ≦ 0.4), and an anisotropic starting material composed of a bismuth layered perovskite type compound A method for producing a crystallographically-oriented ceramic, characterized by employing an acid-treated product obtained by acid treatment. According to claim 1 or 2, as the reaction raw material powders, the general formula _{(3) {Li p (K} 1-q Na q) 1-p} c (Nb 1-rs Ta r Sb s) O 3 ( where, 0 ≦ p ≦ 1, 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, 0 ≦ s ≦ 1, 0.95 ≦ c ≦ 1.05), and a powder made of an isotropic perovskite compound is employed. A method for producing a crystallographic ceramic mix characterized by the above.   In any one of Claims 1-3, the said General formula (1) satisfies the relationship of 9x-5z-17w> = 318 and -18.9x-3.9z-5.8w <=-130. A method for producing a crystallographically-oriented ceramic.