JP4940825B2 - Method for producing piezoelectric ceramic composition - Google Patents

Description

  The present invention relates to a method for producing a piezoelectric ceramic composition.

Conventionally, PZT (PbTiO ₃ —PbZrO ₃ ) component ceramics containing lead have been used as piezoelectric ceramic compositions. This is because the PZT exhibits a large piezoelectricity and has a high mechanical quality factor, and can easily produce materials having various characteristics required for each application such as a sensor, an actuator, and a filter. Moreover, since the PZT has a high relative dielectric constant, it can also be used as a capacitor.

  However, the piezoelectric ceramic composition made of PZT has excellent characteristics, but contains lead as a constituent element, and therefore, harmful lead is eluted from industrial waste of products containing PZT, thereby preventing environmental pollution. There was a risk of causing it. The recent increase in awareness of environmental problems has made it difficult to manufacture products that can cause environmental pollution such as PZT.

Therefore, not containing lead in the composition formula _{{Li X (K 1-Y} Na Y) 1-X} is represented by _{(Nb 1-ZW Ta Z Sb} W) O 3, and x~w each Piezoelectric ceramic compositions based on compounds in the composition range of 0 <x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2 have been developed ( Patent Document 1).

A conventional method for producing such a piezoelectric ceramic composition is as follows, for example. The carbonates of Li, K, and Na and the oxides of Nb, Ta, and Sb are blended based on the stoichiometric ratio, and the blended raw materials are mixed in acetone for 24 hours using a ball mill and dried. Make it. This mixture is calcined, and the calcined mixture is further pulverized in acetone for 24 hours by a ball mill. Subsequently, a binder is added and pressure molding is performed. The molded body thus obtained is fired (main firing) to produce a fired body.
JP 2004-300012 A

  However, the piezoelectric ceramic composition manufactured by the above manufacturing method has a problem of low piezoelectric characteristics.

  As a result of intensive studies on the cause of low piezoelectric characteristics, the inventors have found the following.

  That is, each carbonate of Li, K, Na, etc. has high hygroscopicity or deliquescence, so when using a solvent containing water during wet grinding before mixing and mixing, the stoichiometry of the raw material It is difficult to maintain the ratio, and the piezoelectric characteristics of the piezoelectric ceramic composition produced by firing are reduced.

  Piezoelectric ceramics that are made by firing because the use of a low-polarity solvent that does not contain water, such as acetone, during wet pulverization after pre-firing causes poor pulverization efficiency and makes the composition after firing difficult to be uniform. The piezoelectric properties of the composition are reduced.

  The present invention has been made in view of the above problems, and aims to provide a method for producing a piezoelectric ceramic composition that does not contain lead, has good grinding and mixing efficiency, and has excellent piezoelectric characteristics. To do.

The above object of the present invention is achieved by the following configurations.
1. A method for producing a piezoelectric ceramic composition comprising as a main component a composition represented by the following general formula (1), comprising a compound containing each of Li, K, and Na and each of Nb, Ta, and Sb A method for producing a piezoelectric ceramic composition in which a compound is pulverized and mixed in a solvent that does not contain water and then calcined, and the calcined mixture is pulverized in a solvent that contains water and then calcined.
The compound containing each of Li, K, and Na is a carbonate of Li, K, and Na.
A method for producing a piezoelectric ceramic composition, wherein the composition represented by the general formula (1) is added so that the amount of BiFeO ₃ is less than 1 mol% with respect to the total amount of the composition after the addition. .
General formula (1)
_{{Li x (K 1-y} Na y) 1-x} (Nb 1-z-w Ta z Sb w) O 3
(Where 0 <x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2)
2. 2. The method for producing a piezoelectric ceramic composition according to 1 above, wherein the water-free solvent is an anhydrous alcohol solvent.

  According to the present invention, the stoichiometric ratio of the blended raw materials Li, K, and Na is not easily changed, and the pulverization and mixing efficiency is high and the composition is easily uniformed. This improves the piezoelectric characteristics. Since it does not contain lead, there is no risk of causing environmental pollution, and a piezoelectric ceramic composition with good piezoelectric characteristics can be produced efficiently.

  Below, one Embodiment of the manufacturing method of the piezoelectric ceramic composition which concerns on this invention is described.

The method for producing a piezoelectric ceramic composition according to the present invention is a method for producing a piezoelectric ceramic composition containing as a main component a composition represented by the following general formula (1), and contains each of Li, K, and Na. The compound containing Nb, Ta, and Sb and the compound containing each of Nb, Ta, and Sb are pulverized and mixed in a solvent that does not contain water, and then calcined. It is characterized by firing.
General formula (1)
_{{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)
As a result of diligent research to improve the efficiency of pulverization and mixing in the method for manufacturing a piezoelectric ceramic composition disclosed in Japanese Patent Application Laid-Open No. 2004-300012, the present inventors have a high polarity during wet pulverization and mixing. It has been found that the use of a solvent improves the efficiency of pulverization and mixing compared to the case of using a less polar solvent. It is difficult to maintain the stoichiometric ratio of the raw material when water is used as a solvent at the time of pulverization and mixing before calcination, but after calcination, even if a solvent containing water is used, the blended raw materials Li, K, The present inventors have found that the stoichiometric ratio of Na hardly changes, and thus completed the present invention.

  When using a solvent that does not contain water at the time of pulverization and mixing, the efficiency of pulverization and mixing is reduced. However, the degree of decrease is slight and it is in the usable range. It has been found that the degree of reduction in the efficiency of pulverization and mixing due to moisture absorption and deliquescence of carbonate and the like due to is much greater. On the other hand, after calcination, by using a solvent containing water, the efficiency of pulverization is improved, and even when calcination is insufficient and unreacted alkali metal carbonate or the like remains, this calcination Prior to the treatment, unreacted alkali metal carbonate and the like can be sufficiently removed with a solvent containing water. It is better to first add an excess of alkali metal carbonate, etc., fly to some extent by calcination, and wash the remaining part.

In addition, the composition represented by the above general formula (1) is a main component, and the composition represented by the following general formula (2) is less than 1 mol% with respect to the total composition after addition. When added in this manner, the amount of polarization of the obtained piezoelectric ceramic composition is increased and the relative dielectric constant is improved, whereby a piezoelectric ceramic composition having excellent piezoelectric characteristics can be obtained.
General formula (2)
ABO ₃
(In the formula, A represents Bi, and B represents at least one of Fe, In, Sc, Y, and Mn)
In the present invention, the main component represented by the general formula (1) has a perovskite structure (ABO ₃ ), the element configuration of the A site corresponds to K, Na, Li, and the element configuration of the B site is It corresponds to Nb, Ta, Sb. By adding the composition represented by the general formula (2) as a subcomponent in a combination represented by BiBO ₃ (Bi corresponds to an element at the A site) having a perovskite structure, a piezoelectric obtained The remanent polarization of the porcelain composition can be significantly increased to improve the piezoelectric characteristics. The reason why the piezoelectric properties are improved is that Bi is added to Bi ₂ O ₃ alone and becomes +5 valent, and is easily replaced with the B site, but a combination of BiBO ₃ (for example, BiFeO ₃ ) known to have a perovskite structure. This is considered to be because it becomes +3 valence and is easily replaced with the A site.

  In this invention, the piezoelectric ceramic composition which has as a main component the composition represented by the said General formula (1) is manufactured as follows.

As raw materials, Li-containing compounds include Li ₂ CO ₃ , Li ₂ O, LiNO ₃ , LiOH and the like, and Na-containing compounds include Na ₂ CO ₃ , NaHCO ₃ , NaNO _{3 and the} like, including K. the compound, a _{K 2 NO 3, KNO 3,} KNbO 3, KTaO 3 , etc., Examples of the compound containing _{Nb, Nb 2 O 5, Nb} 2 O 3, NbO 2 , etc., as a compound containing Ta Sb ₂ O ₅ , Sb ₂ O ₃ , Sb ₂ O _4, etc. are prepared as compounds containing Sb, such as Ta ₂ O ₅ .

Here, the compound containing each of Li, K, and Na is preferably a carbonate of Li, K, and Na. That is, as the compound containing Li, a compound containing Li ₂ CO _3, Na Examples of the compound containing Na ₂ CO _3, K, preferably K ₂ C O _3. Since it contains only Li, K, Na and volatile components, the stoichiometric ratio after firing can be easily determined when the raw materials are blended.

  The raw materials are sufficiently dried, each dried raw material is weighed based on the stoichiometric ratio, and mixed and dried in a solvent not containing water by a ball mill or the like. When water is used as a solvent during pulverization and mixing before calcination, it is difficult to maintain the stoichiometric ratio of the raw materials. Therefore, a solvent that does not contain water is used. The solvent not containing water is preferably an organic solvent, and examples of the organic solvent include alcohol solvents, polyhydric alcohol solvents, ether solvents, ketone solvents, ester solvents, and the like.

  Examples of alcohol solvents include methanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, and methylcyclohexanol.

  Examples of the polyhydric alcohol solvent include ethylene glycol monomethyl ether, ethylene glycol monoacetate, diethylene glycol monomethyl ether, diethylene glycol monoacetate, propylene glycol monoethyl ether, propylene glycol monoacetate, dipropylene glycol monoethyl ether, propylene glycol monomethyl ether, Mention may be made of propylene glycol monopropyl ether, methoxybutanol, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol propyl ether, dipropylene glycol monobutyl ether and the like.

  Examples of ether solvents include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane, dioxane and the like.

  Ketone solvents include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonyl acetone, dimethyl oxide, phorone, cyclohexanone, diacetone. Alcohol etc. can be mentioned.

  Ester solvents include ethyl formate, methyl acetate, ethyl acetate, butyl acetate, cyclohexyl acetate, methyl propionate, ethyl butyrate, ethyl oxyisobutyrate, ethyl acetoacetate, ethyl lactate, methoxybutyl acetate, diethyl oxalate, diethyl malonate Etc.

  1 type may be used for said solvent and it can also be used in combination of 2 or more type.

  Among these organic solvents, highly polar solvents are preferable, and alcohol solvents are particularly preferable. By using an anhydrous alcohol solvent as an organic solvent that does not contain water in this way, the efficiency of pulverization and mixing is further improved, so that the piezoelectric ceramic composition piezoelectric material produced by further pulverization and mixing time reduction and firing is further improved. The characteristics can be improved. Of anhydrous alcohol solvents, anhydrous methanol, anhydrous ethanol, and anhydrous propanol are particularly preferable.

  Subsequently, the mixture is calcined at about 700 to 800 ° C. to decompose the raw material and form a solid solution by solid phase thermochemical reaction. The obtained mixture after calcination is pulverized in a solvent containing water into fine particles having a center particle diameter of about 5 μm and dried to obtain a calcination powder.

  As a solvent containing water, pure water is preferable, but it may be mixed with an organic solvent compatible with water.

  An organic binder (binder, etc.) is added to the calcined powder, granulated, and pressed. In the pressure molding, it is preferable that a granulated pulverized product is molded into a pellet by uniaxial press molding or the like and further remolded by cold isostatic pressing (CIP) or the like.

  The molded body thus obtained is fired (mainly fired) at about 1000 to 1300 ° C. to produce a fired body. The obtained fired body is cut into a predetermined size and subjected to parallel polishing, and then electrodes are formed on both surfaces of the sample by sputtering or the like. Then, a direct current voltage of 1 to 6 kV / mm is applied between the electrodes in a silicone oil of about 80 to 150 ° C., and polarization is applied in the thickness direction to produce a piezoelectric ceramic composition.

Furthermore, the composition represented by the following general formula (2) General formula (2)
ABO ₃
(In the formula, A represents Bi, and B represents at least one of Fe, In, Sc, Y, and Mn)
Is added as follows.

Secondary component represented by the general formula (2) is preferably added to the main component compounds constituting the BiBO ₃ type perovskite compound, and BiBO ₃ type perovskite compound in the step of mixing a main component It is good also as adding combining a raw material.

When a compound constituting a BiBO ₃ type perovskite compound is added to the main component, for example, BiFeO ₃ , BiMnO ₃ , BiYO ₃ or the like is prepared as an additive. Specifically, as a raw material of the additive, for example, Bi ₂ O ₃ as a compound containing Bi, In ₂ O ₃ as a compound containing In, Sc ₂ O ₃ , Fe as a compound containing Sc Fe ₂ O ₃ as a compound containing, as the compound containing Y prepare Mn ₂ O ₃ as a compound containing Y ₂ O _3, Mn, thoroughly dried, generally each raw material after drying Weigh based on the stoichiometric ratio such that the formula BiBO ₃ is obtained, and wet mix to obtain additive mixed powder.

  The additive mixed powder and the main component calcined powder obtained by the above method are less than 1 mol% with respect to the total amount of powder after the addition mixed powder (main component calcined powder + additive mixed powder). Blend as follows. The blended material is sufficiently mixed and dried by a ball mill or the like to prepare a mixture. And after calcining the obtained mixture at about 700-800 degreeC, it grind | pulverizes in a pure water.

  The obtained calcined powder is subjected to molding, firing (main firing), electrode formation, and polarization in the same manner as described above to produce a piezoelectric ceramic composition.

Hereinafter, the present invention will be described in detail by experimental examples.
Sample 1.
First, high purity Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ and Sb ₂ O ₅ with a purity of 99% or more were prepared. These raw materials are sufficiently dried, and in the general formula {Li _x (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ , x = 0.04, y = 0. 52, z = 0.1, w = 0.06, that is, the general formula is {Li _0.04 (K _0.48 Na _0.52 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.06 ) O ₃ The stoichiometric ratio was blended. The blended raw materials were pulverized in absolute ethanol for 24 hours by a ball mill, mixed and dried to prepare a mixture. Subsequently, the mixture was calcined at 750 ° C. for 5 hours, and the calcined mixture was pulverized in pure water with a ball mill for 24 hours.

Subsequently, polyvinyl butyral was added as a binder, granulated, and subjected to pressure molding. In the pressure molding, the granulated pulverized product was molded into a pellet by uniaxial press molding, and further remolded at a pressure of 1 ton / cm ² by cold isostatic pressing (CIP).

  The molded body thus obtained was fired at 1000 to 1300 ° C. for 1 hour (main firing) to produce a fired body. In addition, the temperature which becomes the maximum density between 1000-1300 degreeC was selected for the calcination temperature at this time.

The obtained fired body was cut into a predetermined size and subjected to parallel polishing, and then electrodes were formed on both surfaces of the sample by sputtering. Then, a DC voltage of 5 kV / mm was applied between the electrodes in 100 ° C. silicone oil, and polarization was applied in the thickness direction to produce a piezoelectric ceramic composition.
Samples 2-5.
A piezoelectric ceramic composition was prepared in the same manner as Sample 1 except that the raw materials were pulverized and mixed in the solvent shown in Table 1A, and the mixture after calcination was pulverized in the solvent shown in Table 1B. .
Sample 6
High purity Bi ₂ O ₃ and Fe ₂ O ₃ having a purity of 99% or more were prepared. These raw materials were blended at a stoichiometric ratio so as to be BiFeO ₃ to obtain an additive mixed powder. The mixture after calcining obtained by the same method as Sample 1 so that the added powder mixture is 0.6 mol% with respect to the total amount of powder after addition (main component calcined powder + added powder mixture) The mixture was mixed and pulverized in pure water with a ball mill for 24 hours. Next, this mixture was calcined at 700 to 800 ° C. for 5 hours, and this calcined mixture was pulverized in pure water for 24 hours by a ball mill. Subsequently, pressure molding and firing (main firing) were performed in the same manner as Sample 1, and electrode formation and polarization treatment were performed to prepare a piezoelectric ceramic composition.

Next, sample No. 1-No. For No. 6, the piezoelectric d ₃₁ constant and the relative dielectric constant εr were measured. Here, the piezoelectric d ₃₁ constant was measured by a resonance-antiresonance method using an impedance analyzer (4294A manufactured by Agilent Technologies). The relative dielectric constant εr was measured at a measurement frequency of 100 kHz using an impedance analyzer (4294A manufactured by Agilent Technologies). The results are shown in Table 1.

As is apparent from Table 1, the piezoelectric ceramic composition (sample 6 ) produced by the method of the present invention is more than the piezoelectric ceramic composition (samples 3, 4, and 5) produced by a conventionally known method. It was confirmed that the piezoelectric d ₃₁ constant was improved. According to the method of the present invention, a piezoelectric ceramic composition excellent in piezoelectric characteristics could be produced in a piezoelectric ceramic composition that does not contain lead and therefore does not cause environmental pollution.

  In Sample 6, a piezoelectric ceramic composition with improved relative dielectric constant and excellent piezoelectric characteristics could be produced.

Claims (2)

A method for producing a piezoelectric ceramic composition comprising as a main component a composition represented by the following general formula (1), comprising a compound containing each of Li, K, and Na and each of Nb, Ta, and Sb A method for producing a piezoelectric ceramic composition in which a compound is pulverized and mixed in a solvent that does not contain water and then calcined, and the calcined mixture is pulverized in a solvent that contains water and then calcined.
The compound containing each of Li, K, and Na is a carbonate of Li, K, and Na.
A method for producing a piezoelectric ceramic composition, wherein the composition represented by the general formula (1) is added so that the amount of BiFeO ₃ is less than 1 mol% with respect to the total amount of the composition after the addition. .
General formula (1)
_{{Li x (K 1-y} Na y) 1-x} (Nb 1-z-w Ta z Sb w) O 3
(Where 0 <x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2)   The method for producing a piezoelectric ceramic composition according to claim 1, wherein the water-free solvent is an anhydrous alcohol solvent.