JPS61122124A - Production of piezoelectric ceramic powder - Google Patents

Abstract

PURPOSE:To produce the titled powder having fine particle size and giving a sintered material having excellent flexural strength, by adding Sb2O3 and ammonia water to a mixed aqueous solution of nitric acid containing lead nitrate, Ti, Zr, and Sn, separating the precipitated composite by filtration, and calcining the composite. CONSTITUTION:A nitric acid aqueous solution of titanium oxynitrate is prepared e.g. by adding an aqueous solution of nitric acid to titanium tetrapropoxide or titanium tetrabutoxide. The aqueous solution is further added with lead nitrate, zirconium oxynitrate and stannous acetate to obtain a mixed aqueous solution of nitric acid. Antimony oxide and a precipitant consisting of ammonia water are added to the aqueous solution to effect the coprecipitation of a composite composed of the elements of Pb, Ti, Zr and Sn. The precipitate is filtered, washed, dried, calcined at 550-800 deg.C, crushed, and dried to obtain the objective piezoelectric ceramic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing piezoelectric ceramic powder made of lead zirconate tin antimonate titanate and used for filters, spark plugs, etc.

Structure of the conventional example and its problems The conventional piezoelectric ceramic powder made of tin antimonate titanate lead zirconate has a P of 1 as shown in Fig. 1.
bo, Tie. , ZfO□, SnO2,5b
Various oxide powders of 203 are blended according to the target composition, mixed in a wet ball mill, dried in step 2, calcined in step 3 for solid phase reaction, pulverized in step 4 with a wet ball mill, and dried in step 5. Manufactured by The disadvantages of this method are that the degree of homogeneity of the composition is poor from a microscopic point of view, and the powder particle size is also relatively large, making it difficult to reduce the particle size to 1 μm or less. For this reason, when the sintered body was processed into a thin plate, the strength of the thin plate was insufficient.

However, when used as a filter, if the resonant frequency is in the fusion zone, thickness vertical vibration or thickness shear vibration is used. In this case, the resonant frequency is determined by the material constant and the thickness of the element, and the higher the resonant frequency, the thinner the element is required to be.

For example, for a material with a frequency constant of 9501-1z-m,
The element thickness is approximately 210μ to obtain a resonance frequency of 4.6-
m.

Therefore, homogeneous and fine-grained piezoelectric ceramic powder is required. The coprecipitation method and the alkoxide method are known as methods for producing homogeneous fine particles.

Although the synthesis of lead zirconate titanate and PLZT using the coprecipitation method is already known in the literature, the synthesis becomes more difficult as the number of components increases. Furthermore, in the alkoxide method, each component metal alkoxide must be synthesized once, making the production process complicated and impractical.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for producing piezoelectric ceramic powder made of lead zirconate tin antimonate titanate, which is homogeneous and has a small powder particle size, by a coprecipitation method.

Constitution of the Invention In order to achieve the above objects, the present invention provides lead nitrate, titanium oxynitrate, and zirconium oxynitrate.

In the process of co-precipitating a composite consisting of the elements Pb, Ti, Zt, and Sn from a mixed nitric acid aqueous solution of stannous acetate using an ammonia aqueous solution as a precipitant, antimony oxide was added and mixed to remove the precipitate. After the formation, the precipitate is passed through,
This is a method for producing piezoelectric ceramic powder, which is characterized by washing, drying, and calcining at sso'c to aOO°C. Titanium oxynitrate is prepared by adding an aqueous nitric acid solution to titanium tetraproboxoxide or titanium tetrabutoxide, or by converting titanium tetrachloride into titanium hydroxide with aqueous ammonia and adding an aqueous nitric acid solution thereto.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the flowchart shown in FIG. 2. Starting materials are weighed so as to have the desired composition and subjected to the following treatment. At 6 in Fig. 2, lead nitrate Pb(NO3)2 and t -? Zirconium nitrate zrO(NO3)21
12H2° was dissolved in pure water, mixed with a 6-fold diluted nitric acid aqueous solution of titanium tetraproboxoxide T I (QC3H7)4 to form a titanium oxynitrate Ti0(NO3)2 solution, and stannous acetate was diluted 6-fold. Dissolve in aqueous nitric acid solution. These are added to a nitric acid aqueous solution and stirred to obtain a mixed nitric acid aqueous solution for coprecipitation. The pH of this aqueous solution is approximately 1. As shown in T, the desired composition of antimony oxide 5b203 was weighed out. Using a mixer in the reaction tank,
Add diluted ammonia water 8 and add antimony oxide powder while stirring strongly, and as shown in 9, mix the mixed nitric acid aqueous solution for coprecipitation and the ammonia water bath solution as a precipitant until the pH of the liquid in the reaction tank is 7. Add while adjusting it so that it is in the range of ~8. The precipitate obtained in this operation was filtered and washed as shown in 10, then dispersed in pure water and spray-dried as shown in 11. This powder was calcined at a temperature of 600°C for 2 hours as shown in 12, pulverized in a wet ball mill as shown in 13, and dried as shown in 14. Ceramic powder was produced. The particles of the precipitate produced by this method are very fine particles, on the order of 100 particles, except for the antimony oxide added in the form of powder. Therefore, the reactivity is good, and it was confirmed by X-ray analysis that a single-phase crystal structure of perovskite is formed at a calcination temperature of around 550''C. The calcination temperature was approximately 860°C.The average particle size of the powder was also 0.8 μm, which was smaller than 1.6 μm in the conventional method.

Next, using the method of the present invention and the conventional method, powders of lead zirconate tin antimonate titanate were made with different compositions, and thin plates were sliced to a thickness of 200 pm from these sintered bodies. The bending strengths were compared. The results are shown in the table below. When the powder produced by the method of the present invention is used, the bending strength of the sintered body is improved.

Result of bending strength measurement Composition Pb(Sn, ASbH)xTi, Zr2O3(z
+y+z=1) In the method of the present invention, antimony is added in the form of oxide powder, but the melting point of antimony oxide is 666
It was added in the form of an oxide, noting that since it is as low as 10°C, it is easy to react even at a relatively low temperature during calcination.

In this example, titanium oxynitrate Tio(NO3)2
was made from titanium tetraproboxoxide, but similar results can be obtained by adding a nitric acid aqueous solution to titanium tetrabutoxide, or by making titanium tetrachloride into titanium hydroxide with ammonia water and adding a nitric acid aqueous solution to this. It will be done. In addition, if the calcination temperature is lower than 550"C, the reaction due to calcination will not be sufficient, and if it is higher than 800"C, the particle size will grow large, the reactivity will decrease, and fine particles will be formed by the coprecipitation method. It becomes unsuitable for that purpose.

Effects of the Invention As mentioned above, the tin antimonate titanate lead zirconate powder produced by the method of the present invention is fine particles, and the sintered body obtained from it has a higher bending strength than that of the conventional method. It is strong and highly effective for applications where it is used as a thin plate such as high frequency filters.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the manufacturing process of piezoelectric ceramic powder according to a conventional method, and FIG. 2 is a flowchart showing the manufacturing process of piezoelectric ceramic powder according to an embodiment of the present invention.

Claims (2)

[Claims] (1) Using an aqueous ammonia solution as a precipitant, Pb, Ti, Zt,
In the process of co-precipitating a composite consisting of each element of Sn, antimony oxide is added and mixed to form a precipitate, then the precipitate is filtered, washed, dried, and calcined at 550°C to 800°C. A method for producing piezoelectric ceramic powder, characterized by: (2) Titanium oxynitrate is made by adding a nitric acid aqueous solution to titanium tetraproboxoxide or titanium tetrabutoxide, or titanium tetrachloride is made into titanium hydroxide with aqueous ammonia, and a nitric acid aqueous solution is added thereto. A method for producing piezoelectric ceramic powder according to claim (1).