JPH0457617B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a raw material powder of a piezoelectric composite perovskite structure compound and its solid solution (hereinafter referred to as perovskite). Piezoelectric perovskites are widely used as functional ceramics such as ceramic filters, piezoelectric acoustic devices, actuators, and ultrasonic devices. Recently, it has been desired to further improve this functionality, and it is possible to efficiently produce large quantities of perovskite raw material powder that is easy to sinter, has uniformity, has high bulk density, and is low cost to meet this demand. There is a need for the development of technology that can do this. (Prior Art and its Problems) Dry methods, coprecipitation methods, and multi-stage wet methods are conventionally known as methods for producing perovskite raw material powders. The dry method is a method in which compounds of constituent raw materials are mixed in a dry method and then calcined. However, with this method, it is difficult to obtain a raw material powder with a uniform composition, so it is difficult to obtain a perovskite with excellent functionality, and the sinterability is also not sufficient. The coprecipitation method is a method in which a mixed solution is prepared by combining all of the constituent components, a precipitate-forming liquid such as an alkali is added to the mixed solution to cause coprecipitation, and the coprecipitate is dried and calcined. According to this coprecipitation method, it is easy to obtain powder with excellent uniformity, but because of its uniformity, the particles coagulate to form secondary particles during precipitate formation, drying, or calcination, making it easy to sinter. I had a flaw that made it difficult to become sexually sensitive. In addition, in the coprecipitation method, if the precipitate forming ability of each component in the precipitate forming solution is not the same, for example, one component will form substantially 100% of the precipitate, while other components will form substantially all of the precipitate. In some cases, it may be difficult to obtain the desired composition, especially when the Mg component,
It was difficult to precipitate substantially 100% of the Zn component, Ni component, and Mn component. The multi-stage wet method is disclosed in JP-A No. 61-53113 and JP-A-Sho.
As described in Publication No. 61-53115, etc., the above-mentioned drawbacks of the coprecipitation method are solved by precipitating each component in stages. However, the perovskite obtained by this manufacturing method has a drawback in that it does not have sufficient piezoelectric properties. (Objective of the Invention) An object of the present invention is to provide a method for producing perovskite with excellent piezoelectric properties by improving the multi-stage wet method. Another object of the present invention is to provide a method for efficiently producing piezoelectric perovskite and its solid solution raw material powder that satisfies the four requirements of easy sinterability, uniformity, low cost, and high bulk density. It is. (Technical Means for Solving the Problems) The present inventors have conducted intensive research to achieve the above object, and as a result, have arrived at the present invention. The present invention uses the general formula x[Pb(Zn _1/3 Nb _2/3 )O ₃ ]-y
( _PbTiO3 )-z( _PbZrO3 )-a( _MnO2 )-b( _Al2
O ₃ ) (where x, y and z indicate mol%,
x+y+z=100, and a and b are x+y+
molar ratio to z=100, a=0.05 to 5,
b=0 to 5. ) Pb, Nb,
After contacting the solution of each component of Ti, Al and Zr with a precipitate forming solution to form a precipitate of each component in stages,
Adjust the concentration of ions generated from the precipitate-forming agent in the precipitate-containing liquid to 0.2 mol/or less, and then adjust the pH of the precipitate-containing liquid to 11.5 or less with the precipitate-forming liquid, and then add each component of Mn and Zn. The present invention relates to a method for producing an easily sinterable piezoelectric perovskite raw material powder, which is characterized by adding a solution, forming a precipitate of each component, and calcining the obtained precipitate. In the present invention, the term "solution" refers to a solution in which soluble substances are dissolved or a suspension in which insoluble substances are dispersed. The values of x, y and z in the above general formula can take various values depending on the use of the piezoelectric material, but usually x
is preferably selected from the range of 5 to 90, y of 5 to 80, and z of 5 to 80 mol%. If it is outside this range, the piezoelectric properties will deteriorate, which is not preferable. a and b are molar ratios to x + y + z = 100,
a ranges from 0.05 to 5, and b ranges from 0 to 5. Both Mn and Al have the effect of improving the mechanical quality factor Qm, but excessive addition is undesirable because it lowers the dielectric constant. Pb component, Nb component of perovskite
Component compounds for preparing solutions of compounds of Ti component, Al component, and Zr component are not particularly limited, but include their hydroxides, carbonates,
Inorganic salts such as oxysalts, sulfates, nitrates, chlorides,
Appropriate selection is made from organic acid salts such as acetate and oxalate, oxides, etc. Further, as compounds of Mn and Zn components, their nitrates, chlorides, hydroxides, etc. are used. These are generally used as an aqueous solution, but if they are not soluble in water, they can be made soluble by adding an acid, and insoluble raw materials may be used as a suspension solution. Examples of the precipitate-forming liquid include solutions of ammonia, ammonium carbonate, caustic alkali, amine, oxalic acid, alkylamine, and the like. Examples of alkylamines include primary amines having a lower alkyl group such as methylamine, ethylamine, propylamine, and butylamine, primary amines having a lower alkyl group such as cyclohexylamine, secondary amines having a lower alkyl group such as dimethylamine and diethylamine, and triethylamine. Mention may be made of tertiary amines having lower alkyl groups such as To form a precipitate of the constituent components, an aqueous solution of each constituent component may be added to the precipitate forming liquid while stirring the precipitate forming liquid, or vice versa.
It is preferable that the addition be carried out while sufficiently stirring the liquid. A specific method of contacting a solution of each component of Pb, Nb, Ti, Al, and Zr with a precipitate forming solution to form a precipitate of each component in a stepwise manner is as follows: (1) Zr, Al
A method in which a precipitate of each component is generated using a precipitation forming solution from a solution in which a compound of Ti and Nb is dissolved or dispersed, and a solution of a compound of Ti and Nb, or (2) a solution in which a compound of Nb is dissolved or dispersed. From the dispersed solution and the solutions of the Pb compound, Zr compound, and Al compound, a precipitate is used to form a precipitate of the Nb component, Pb component, Zr component, and Al component, and then the Ti compound is precipitated. Preferred examples include a method in which a solution is added to form a precipitate of the Ti component. In the method (1) or (2) above, Pb
In order to generate precipitates of Nb component, Ti component, Al component and Zr component, each component solution may be added to the precipitate forming liquid while stirring the precipitate forming liquid, or vice versa. You may. Further, each component solution may be brought into contact with the precipitate forming solution in multiple stages or alternately as necessary. The precipitate obtained by the above method is washed with water or the like by a normal washing method such as a decantation method to reduce the concentration of ions generated from the precipitate forming agent in the precipitate-containing liquid.
Adjust so that it is 0.2 mol/or less. By setting the concentration of ions generated from the precipitant to 0.2 mol/or less, Cl ^- and NO ^- ₃ ions in the solution, which are undesirable impurities, can be removed. Next, the pH of the precipitate-containing solution is adjusted to 11.5 or higher, preferably 12.0 to 12.5, using a precipitate-forming solution, and solutions of Mn and Zn components are added to form precipitates of these components. The precipitate obtained by the above method can be filtered, dried, and then calcined without any washing. According to this method, it is possible to prevent the elution of precipitates of Mn and Zn components due to washing, which has been a problem in the past, and it is possible to obtain a perovskite raw material powder having a desired composition. The precipitate may be dried under atmospheric pressure or under reduced pressure. If the calcination temperature is too low, the dehydration and thermal decomposition of the precipitate will be insufficient, and if it is too high, the powder will become coarse, so the calcination temperature is usually 500 to 900.
A range of 0.degree. C. is preferred. (Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below. Example 1 25 [Pb (Zn _1/3 Nb _2/3 ) O ₃ ] −40 (PbTiO ₃ ) −35
( _PbZrO3 )-2( _MnO2 )-0.5( _Al2O3 ) 4.34g of niobium pentoxide ( _Nb2O5 ) powder was dispersed in 500ml of _{a 4.5N} ammonia aqueous solution. Next, 64.92 g of lead nitrate [Pb(NO ₃ ) ₂ ] was added to this suspension.
and zirconyl nitrate [ZrO(NO ₃ ) ₂・2H ₂ O] 18.34
g and aluminum nitrate [Al(NO ₃ ) ₃・9H ₂ O]
A solution prepared by dissolving 3.75 g of titanium tetrachloride (TiCl 4 ) in 1 part of water was added dropwise, and then a solution prepared by dissolving 14.87 g of titanium tetrachloride (TiCl ₄ ) in 300 ml of water was added dropwise. Next, the formed precipitate was repeatedly decanted with water,
Wash and reduce ammonium ion concentration to 0.1 mol/
and then add 200ml of an aqueous solution containing 20ml of diethylamine.
ml was added to adjust the pH to 12.0. A solution of 4.84 g of zinc nitrate [Zn( _{NO 3} ) _{2.6H 2} O] and 1.15 g of manganese nitrate [Mn(NO ₃ ) 2.6H ₂ O] dissolved in 300 ml of water was gradually added to this solution to precipitate it. generated. This precipitate was separated by filtration without washing, dried, and then analyzed for composition, and the elemental composition was found to be the same as that of the initial precipitate. Further, this precipitate was calcined at 750°C for 2 hours. The particle diameter of the obtained calcined powder was 0.21 μm or less and uniform, as observed by TEM photography. After adding 0.2% polyvinyl alcohol to this calcined powder and molding it into a disk of 1mmt x 16mmφ,
It was baked at ℃ for 2 hours. The density of the obtained sintered body was measured by the Archimedes method and was found to be 7.93 g/cm ³ , which is close to the theoretical density. After baking Ag electrodes on both sides of the disk of this sintered body and polarizing it with an electric field of 10 kV/cm at 140°C, the piezoelectric properties were measured.
The following results were obtained. Relative dielectric constant ε ₃₃ /ε ₀ 752 Electromechanical coupling coefficient Kp 38% Mechanical quality factor Qm 3250 Example 2 In Example 1, niobium pentachloride (NbCl ₅ ) was used instead of niobium pentoxide as the niobium source. Perovskite powder was produced in the same manner as in Example 1 except that the firing temperature was changed from 750°C to 700°C. The obtained calcined powder was a uniform powder with a particle size of about 0.1 μm. The density of the sintered body is 7.96g/cm ³
The piezoelectric properties were as follows: dielectric constant ε ₃₃ /ε ₀ 823 electromechanical coupling coefficient Kp 40% mechanical quality coefficient Qm 3380. Examples 3 to 6 Perovskite powders were manufactured using the manufacturing method of Example 1 except that the ratios of the constituent elements were changed as shown in Table 1. Table 2 shows the average particle diameter of the calcined powder, the density of the sintered body, and the piezoelectric properties.

【table】

[Table] Comparative example 1 25 [Pb (Zn _1/3 Nb _2/3 ) O ₃ ] −40 (PbTiO ₃ ) −35
(PbZrO3 ₎ -2( _MnO2 )-0.5( _Al2O3 ) Niobium pentoxide ( _Nb2O5 ) _22.2g , lead oxide (PbO) 223.2g, _titanium oxide ( _TiO2 ) 32.0g, zirconium oxide ( ZrO ₂ ) 43.1g, zinc oxide (ZnO) 3.4g, aluminum oxide (Al ₂ O ₃ ) 0.51
g, 1.7 g of manganese oxide (MnO ₂ ) and a small amount of water were added, thoroughly crushed and mixed, and then dried. This was calcined at 750°C for 2 hours. The composition ratio of the obtained calcined powder was the same as in Example 1, but the particle
A TEM photograph showed that the particle size was 1 to 2 μm and nonuniform. Add 0.2% polyvinyl alcohol to this calcined powder.
% was added and molded, and then fired at 1100° C. for 2 hours, and the density of the sintered body was 7.46 g/cm ³ . Although polarization treatment was performed in the same manner as in Example 1, polarization could not be achieved. Comparative Example 2 The calcined powder obtained in Comparative Example 1 was molded by the same treatment and then calcined at 1300° C. for 2 hours. The density of the sintered body was 7.71 g/cm ³ . When we measured the piezoelectric properties after polarization treatment, we found that the electromechanical coupling coefficient was
Kp was 31%. Mechanical quality factor Qm is 2380
It was hot. (Effect of the invention) General formula x[Pb(Zn _1/3 Nb _2/3 )O ₃ ]−y(PbTiO ₃ )−
z( _PbZrO3 ) _-a ( _MnO2 )-b( _Al2O3 ) (however,
x, y and z indicate mol%, x+y+z=
100, a and b are molar ratios to x+y+z=100, a=0.05-5, b=0-5. ) When producing the raw material powder of piezoelectric composite perovskite represented by
Precipitates of Pb, Nb, Ti, Al and Zr components are generated in a sequential stepwise manner, and then, after regulating the concentration and pH of ions generated from the precipitant in the precipitate-containing liquid, Mn and Zn components are precipitated. In order to
It is possible to completely precipitate components that were difficult to precipitate 100% using the coprecipitation method, and as a result of obtaining a precipitate in which two or more phases are highly interdispersed, coagulation and coagulation occur during precipitate formation. Alternatively, it is possible to produce piezoelectric powder with high bulk density and easy sintering properties with good reproducibility and which does not easily cause aggregation during drying and calcining.
Furthermore, compared to powder produced by the widely used dry method, the sintering temperature is lowered by 150 to 250°C, making it very advantageous from an industrial perspective. Furthermore, the piezoelectric properties are also good. In addition, in this process, each phase is highly mutually dispersed, so that the calcined material achieves sufficient uniformity. Further, since the process is simple, it has excellent effects such as being able to obtain easily sinterable powder with good reproducibility and at low cost.

Claims (1)

[Claims] 1 General formula x[Pb(Zn _1/3 Nb _2/3 )O ₃ ]-y(PbTiO ₃ )
-z( _PbZrO3 )-a( _MnO2 )-b( _{Al2O3 )} (where x, y and z indicate mol%, x+y+z
=100, a and b are molar ratios to x+y+z=100, a=0.05-5, b=0-5. ) When producing the raw material powder of the piezoelectric composite perovskite structure compound and its solid solution, solutions of each component of Pb, Nb, Ti, Al, and Zr are brought into contact with a precipitation forming solution to precipitate each component in stages. After the precipitate-containing liquid is produced, the concentration of ions generated from the precipitate-forming agent in the precipitate-containing liquid is adjusted to 0.2 mol/or less, and then the PH of the precipitate-containing liquid is adjusted to 11.5 or less with the precipitate-containing liquid. A method for producing an easily sinterable piezoelectric perovskite powder, which comprises adding solutions of each of Mn and Zn, forming a precipitate of these components, and calcining the obtained precipitate.