JPH0712932B2 - Method for producing perovskite compound containing Pb - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perovskite compound represented by PbMO ₃ (where M is at least one of transition metals) or a composite thereof, which is suitable for piezoelectric ceramic materials and dielectric ceramic materials. {Pb (Fe _1/2 Nb _1/2 ) O ₃ } _x − {Pb (Fe _2/3 W _1/3 ) O ₃ } (
_1-x ) and a method for producing a composite perovskite compound.

[Prior art and its problems]

This kind of compound is a solid solution of Pb oxide and M oxide. Conventionally, it is necessary to mix crushed products of these oxides or crush the mixed product and then sinter. Was manufactured by. However, the pulverization degree of PbO is poor, and the particle size of PbO is about 1.5μ, whereas the other oxides have a particle size of about 0.2μ, so the solid solution state is difficult to be uniform. For this reason, for example, pyrochlores (compounds with a pyrochlore structure) such as PbNb ₂ O ₆ exist, and these pyrochlores do not disappear even when fired at a high temperature of 1000 ° C or higher, and therefore those with a high dielectric constant can be reproducibly reproduced. It was difficult to manufacture. In addition, since a firing temperature of 1000 ° C or higher is required, expensive palladium has to be used as an internal electrode when manufacturing a capacitor, for example.

Therefore, an object of the present invention is to obtain a Pb-containing perovskite compound or a composite compound in which a compound such as pyrochlore does not exist, a solid solution state is uniform, a firing temperature is low, and a high dielectric constant is obtained with good reproducibility. A method of producing a perovskite compound is provided.

[Means for solving problems]

The present invention achieves the above object by using Pb alkoxide without using PbO as a Pb raw material.

That is, the first invention is a method for producing a perovskite compound represented by PbMO ₃ (where M is at least one of transition metals), wherein the oxide of M and the Pb alkoxide are in a molar ratio.
Mix so that M: Pb becomes 1: 1 and crush and add water,
This is a method for producing a Pb-containing perovskite compound by hydrolyzing a Pb alkoxide, filtering and drying the resulting powder, and then calcining the powder.

The second invention is a composite containing Pb by mixing a plurality of oxide powders and a Pb alkoxide, adding water to hydrolyze the Pb alkoxide, filtering and drying, and molding and firing the powder. It is a method for producing a perovskite compound.

Examples of the present invention will be described below.

First, Pb alkoxide, which is one of the starting materials, was obtained by reacting lead nitrate with ethylene glycol, or Na metal was reacted with alcohol to obtain Na alkoxide. The one obtained by reacting with and is used, but the former is more preferable.

Example 1 Pb alkoxide, Fe ₂ O ₃ and Nb ₂ O ₅ were used in a molar ratio of Pb: F
A mixture was prepared by mixing so that e: Nb = 2: 1: 1. Separately, Pb alkoxide, Fe ₂ O ₃ and WO ₃ were added in a molar ratio of Pb: F
A mixture B was prepared by mixing so that e: W was 3: 2: 1.

Subsequently, the mixture A and the mixture B were mixed in predetermined amounts. If the A mixture is x when the whole is 1, then the B mixture is (1-
x). Here, x = 0.67; the B mixture was 0.33.

The mixture is put in a crusher and the temperature is about 2 to 50 at about 40 to 50 ° C.
While pulverizing and stirring for 3 hours, an appropriate amount of distilled water (decarboxylated) was added to hydrolyze the Pb alkoxide. A solid was separated from the solution after the hydrolysis by filtration and washed, and pulverized to obtain a fine powder.

After mixing the fine powder binder obtained, the particles were sized, formed into a single plate, and baked in the air at 900 ° C to produce a composite perovskite {Pb (Fe
Was obtained _{{Pb (Fe 2/3 W 1/3)} O 3} 0.33 - 1/2 Nb 1/2) O 3} 0.67. The density of the obtained fired plate was measured, and a silver electrode was baked again to measure the dielectric constant, dielectric loss and specific resistance. The obtained characteristics are shown in Table 1 together with the characteristics obtained by the conventional method.

In Table 1, the actual density is the theoretical density (8.55
It is the 100-percentage divided by g / cm ³ ).

As is clear from Table 1, the method of the present invention has a higher density than the conventional method. This indicates that the obtained fine powder is uniform and fine.
In addition, due to the high density, mechanical strength (flexural strength, hardness) increases, and intragranular pores decrease, and as shown in Table 1, the dielectric constant, dielectric loss, and specific resistance are also higher than those of the conventional method. Are better.

The fine powder obtained by filtering, washing, and drying as described above was molded into a single plate in the same manner as above, and was fired at 850 ° C. The crystal structures of this fired plate and the above-mentioned 900 ° C. fired plate were examined by X-ray diffraction. The results are shown in FIGS. 1 and 2.

In Fig. 1 for the one fired at 850 ° C, the peak B indicating the pyrochlore appears near the peak value A indicating the perovskite crystal structure, but in Fig. 2 for the one fired at 900 ° C. The mountain indicating pyrochlore does not appear, and the mountain A indicating perovskite appears higher. That is, it indicates that pyrochlore disappears at 900 ° C.

In FIGS. 1 and 2, the peaks other than A and B are the same compounds as A, but those having different crystal planes appear out of phase.

Example 2 Only the A mixture in Example 1 (that is, without mixing with the B mixture) was pulverized, stirred, hydrolyzed, filtered, washed and dried in the same manner as in Example 1 to obtain a fine powder. As in the example, this was molded into a single plate and fired at 900 ° C. Thus, Pb (Fe _1/2 Nb _1/2 ) O ₃ perovskite veneer was obtained. The same characteristics as in Example 1 were measured for this perovskite veneer. The measurement results are shown in Table 2 while being compared with those obtained by the conventional method.

As is clear from Table 2, according to the method of the present invention, it is possible to produce a perovskite compound having a higher density than that of the conventional method and thus a uniform solid solution of uniform oxide particles at a low sintering temperature. Characteristics are also good.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a perovskite compound and a complex perovskite compound which have a uniform solid solution state, a high density, and a pyrochlore-free high dielectric constant.

[Brief description of drawings]

FIG. 1 shows the X-ray diffraction pattern of the fired plate when the firing temperature was 850 ° C., and FIG. 2 shows the X-ray diffraction diagram when the firing temperature was 900 ° C.

Claims (5)

[Claims] 1. A process for producing a perovskite compound represented by PbMO ₃ (where M is at least one of transition metals), wherein the oxide of M and the Pb alkoxide are in a molar ratio of M: Pb of 1 :.
A method for producing a perovskite compound containing Pb by mixing Pb alkoxide with water after mixing so as to be 1, hydrolyzing the Pb alkoxide, filtering and drying the resulting powder, and baking. 2. The method according to claim 1, wherein Pb
A method characterized in that an alkoxide obtained by reacting lead nitrate with ethylene glycol is used. 3. A method for producing a composite perovskite compound containing Pb by mixing a plurality of oxide powders with Pb alkoxide, hydrolyzing the mixture, filtering the precipitate, and drying the powder obtained by molding and firing. 4. The method according to claim 3, wherein the amount of Pb, Fe, Nb, W is {Pb (Fe _1/2 Nb _1/2 ) O ₃ } x− {Pb
Pb alkoxide, Fe ₂ O ₃ , Nb ₂ O ₅ and WO ₃ were mixed so as to satisfy (Fe _2/3 W _1/3 ) O ₃ } ( _1-X ) (where 0 <x <1). A method for producing a composite perovskite compound containing Pb as described above, which comprises hydrolyzing, filtering a precipitate, drying and powdering the obtained powder. 5. The method according to claim 3, wherein Pb
A method characterized in that an alkoxide obtained by reacting lead nitrate with ethylene glycol is used.