JPH0688793B2 - Manufacturing method of perovskite raw material powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a raw material powder of a perovskite structure compound and a solid solution thereof (hereinafter referred to as perovskite).

Perovskites are widely used as functional ceramics such as piezoelectric materials, dielectric materials, and dielectric filters. Recently, in order to improve the performance of the functional ceramics, there has been a demand for development of a technique capable of efficiently producing a raw material powder of perovskite which is easily sintered and has a uniform particle size.

Conventionally, as a method for producing a raw material powder of perovskite,
The dry method and coprecipitation method are known.

The dry method is a method in which the compounds of the constituent raw material components are dry mixed and calcined. However, according to this method, since it is difficult to obtain a raw material powder having a uniform composition, it is difficult to obtain a perovskite having excellent functionality, and the sinterability is not sufficient.

The coprecipitation method is a method in which a mixed solution in which all of its constituents are put together is added, a precipitation-forming solution such as Alikari is added to cause coprecipitation, and the coprecipitate is dried and calcined.

According to this coprecipitation method, it is difficult to obtain a powder with excellent uniformity,
There is a drawback that particles are condensed during the formation of a precipitate, during drying or during calcination to form secondary particles, which makes it difficult to sinter.

Further, in the coprecipitation method, when each component does not have the same precipitation-forming ability with respect to the precipitation-forming liquid, for example, a certain component is substantially 100%.
% Precipitates are formed, but it may be difficult to achieve a desired composition because the other components cannot substantially entirely precipitate.

On the other hand, JP-A-51-59400 and JP-B-54-31600 describe a method in which a suspension containing a precipitate by a coprecipitation method is hydrothermally reacted at 150 to 300 ° C.

[Object of the Invention] The present invention is to eliminate the drawbacks of the conventional method and to provide a method capable of efficiently producing a fine perovskite raw material powder which is easily sintered and has good uniformity.

[Structure of the Invention] The present inventors have accomplished the present invention as a result of earnest research to achieve the above object.

The present invention has the general formula X [A (B _a W _b ) O ₃ ] -y [A (B _c Nb _d ).
O ₃ ] (wherein A represents at least one element selected from Pb, Ba, Sr and Ca, and B represents at least one element selected from Mg, Zn, Ni, Co, Cu, Fe and Mn) , A,
b, c and d are values determined by the valence of each of the above elements,
x and y represent mol% and x + y = 100. In the production of the raw material powder of the perovskite-type production compound represented by the formula (4) and its solid solution (hereinafter referred to as perovskite), each solution and / or suspension of the compound containing the above-mentioned constituent elements is brought into contact with a precipitation forming liquid. The present invention relates to a method for producing a perovskite raw material powder, which is characterized in that precipitation of each component is successively produced, and then the pH of the precipitate-containing slurry is adjusted to 8.0 or higher and hydrothermal treatment is carried out at 130 to 300 ° C.

The perovskite raw material powder obtained by the method of the present invention is a fine powder that is easily sinterable and has good uniformity, and is also characterized in that a sintered body can be obtained at a firing temperature lower than that of the conventional method. .

The values of a, b, c, and d in the above general formula are selected so that the total valence of B and W and the total valence of B and Nb become tetravalent, for example, the atoms of W and Nb. Price is 6 and 5 respectively
In the case of valence, (1) when the valence of B element is 2, a = 1/2,
b = 1/2, c = 1/3, d = 2/3, and (2) when the valence of B element is 3, a = 2/3, b = 1/3, c = 1/2 , D = 1/2.

Further, the values of x and y in the above general formula can take various values depending on the use, but usually x is 5 to 95 mol% and y is 5 to 5 mol%.
It is preferable to select from the range of 95 mol%.

The component compound for preparing each solution and / or each suspension of the compound containing the constituent element of perovskite is not particularly limited, but hydroxides, oxides, carbonates, oxy salts, nitrates thereof Inorganic salts such as chlorides, organic salts such as acetates and oxalates, which can be easily removed by heat treatment, are desirable. Among these, hydroxides, oxides and nitrates are preferable. These are generally used as a water or ethanol solution, but hydroxides and liquids in which oxides are suspended are also used. When it is not soluble in water, alkali or acid may be added to make it soluble.

Examples of the precipitate-forming liquid include ammonia, ammonium carbonate, oxalates, amines, etc., which can be easily removed from the constituents.

In order to successively generate the precipitation of each component, the solution or suspension of each of the above-mentioned components may be added to the precipitation forming liquid while stirring the precipitation forming liquid, or vice versa. Good. It is preferable to add the solution while sufficiently stirring it.

When forming a precipitate, for example, after forming a precipitate of one component, washing with water to remove anions, dispersing the precipitate in fresh water, and further adding an aqueous solution of another component and a precipitate forming solution. May form a precipitate.

Furthermore, after the precipitation of Nb, W, A component and / or B component is formed, the precipitation of a compound containing a metal element other than the above is also formed by appropriately selecting the type and concentration of the precipitation forming liquid. Good.

The pH of the precipitate-containing slurry obtained by the above method was adjusted to 8.0.
Or more, preferably adjusted to 8.5 or more, then 130 ~ 300 ℃
Treat with water. The pH can be adjusted with a basic substance such as aqueous ammonia or ammonium carbonate.

An autoclave is generally used as the method for hydrothermal treatment.

By this treatment, the precipitate becomes perovskite precursor particles having a desired metal atom ratio, and uniform crystal particles are obtained.
If the heating (hydrothermal) treatment temperature is too low, crystallization does not proceed sufficiently, making it difficult to obtain a perovskite precursor suitable for sintering, and if too high, it is not economical and The particles have a large particle size. Therefore, it is necessary to carry out the hydrothermal treatment at a temperature of 130 to 300 ° C., and by this heat treatment, a perovskite precursor having uniform crystal particles of 0.025 to 0.30 μm suitable for sintering can be obtained. Hydrothermal treatment time is 1-10
Time is good.

After hydrothermal treatment, when containing a metal element such as Mg, Zn, Ni, or Co, it is preferable to dry as it is because the compound containing the metal element is slightly dissolved in the precipitate-containing slurry. .

By drying the crystal-precipitated particles thus obtained, a compositionally uniform and easily sinterable raw material powder of perovskite having a uniform particle size is produced with good reproducibility. The powder thus obtained has a temperature of 80% compared to the conventional sintering temperature of 850-900 ° C.
Sintering can be performed sufficiently at around 0 to 830 ° C. Further, it is possible to manufacture a perovskite of a multi-component element having a desired metal element composition.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 19 [Pb (Zn _1/3 Nb _2/3 O ₃ ] -29 [Pb (Fe _2/3 W _1/3 ) O ₃ ] -52
[Pb (Fe _1/2 Nb _1/2 O ₃ ] 8.460 g of niobium hydroxide [Nb (OH ₅ )] and tungsten oxide [WO
₃ ] 2.756 g of powder was dispersed in 100 ml of water, and 100 ml of 6N-ammonia water was added thereto, followed by sufficient stirring. Further dissolve the suspension lead nitrate [pb (NO _{3) 2]} solution and iron nitrate which was dissolved in water _{200ml 40.738g [Fe (No 3)} 3 · 9H 2 O] 22.527g of water 200ml solution and zinc nitrate _{[Zn (NO 3) 2 ·} 6H 2 O] 2.317
A solution of g in 100 ml of water was gradually added to form a precipitate. The pH of the precipitate-containing slurry was 11.

After removing the supernatant, the precipitate slurry was hydrothermally treated at 150 ° C. for 4 hours in an autoclave and then evaporated to dryness at 200 ° C.
When the composition of the obtained powder was analyzed, it was the same as the charged elemental composition.

When X-ray diffraction was measured, it had a perovskite structure as shown in FIG.

On the other hand, according to the observation of the transmission electron micrograph, the particle size is
It was uniform at 0.2 μm or less. Although 0.2% of poly beer alcohol was added to this powder and pressure molding was performed, it could be easily molded. When this was baked at 800 ° C for 2 hours, the density was
It was close to the theoretical density of 8.51 g / cm ^3, and could be fired at a firing temperature lower by 50 ° C than in the case of the dry method.

Comparative Example 1 Niobium oxide (Nb ₂ O ₅ ) 1 having the same composition as in Example 1 was used.
5.469g, tungsten oxide (WO ₃ ) 5.562g, zinc oxide (Z
nO) 1.248 g, lead oxide (PbO) 54.882 g, and iron oxide (Fe
₂ O ₃ ) 8,937 g and a small amount of water were added, and the mixture was thoroughly crushed and mixed, and then dried. This was calcined at 700 ° C. for 2 hours. The particles at that time were non-uniform when observed on a transmission electron micrograph and were about 1 to 2 μm.

After 0.2% polyvinyl alcohol was added to this product and pressure-molded, it was baked at 850 ° C for 2 hours, and the density was 8.3.
It was 0 g / cc.

Example _{2 20 [Pb (Zn 1/3 Nb} 2/3 O 3] -25 [Pb (Fe 2/3 W 1/3) O 3] -55
[Pb (Mg _1/3 W _2/3 ) O ₃ ] Niobium hydroxide [Nb (OH) ₅ powder 2.917
g and 12.830 g of tungsten oxide [WO ₃ ] powder were dispersed in 100 ml of water, and 100 ml of 6N-ammonia water was added thereto, followed by sufficient stirring.

Further lead nitrate to the suspension [Pb (No _{3) 2]} solution and iron nitrate which was dissolved in water _{200ml 40.738g [Fe (No 3)} 3 · 9H 2 O] 8.281g
Dissolved in 200 ml of water and magnesium nitrate [Mg (No
_{3) 2} · 6H ₂ O] solution and zinc nitrate were dissolved in 200ml of water and 5.781g [Zn (No ₃₎ the ₂ · 6H ₂ O] _2.440g added slowly a solution was dissolved in water 100ml a precipitate Let The pH of this precipitate slurry was 11. After removing the supernatant liquid, the precipitate slurry was hydrothermally synthesized at 150 ° C in an autoclave and then 2
Evaporated to dryness at 00 ° C. When the composition analysis of the obtained powder was performed, it was the same as the charged elemental composition. On the other hand, according to the observation of the transmission electron micrograph, the particle diameter was 0.2 μm or less and uniform. When 0.4% of polyvinyl alcohol was added to this powder and molded, it was fired at 820 ° C for 2 hours. The density was 8.55 g / cm ^3, which was close to the theoretical density, and the firing temperature was 70 ° C lower than that of the dry method. I was able to bake.

Example 3 Instead of 100 ml of 6N-ammonia water in Example 1, 6N-N was used.
The same operation as in Example 1 was performed except that 100 ml of an aOH aqueous solution was used, and hydrothermal synthesis at 150 ° C. was performed at 250 ° C.

The obtained particle size was 0.2 μm or less, which was very uniform.

When 0.4% of polyvinyl alcohol was added to the powder to form the powder, the powder was fired at 800 ° C. for 2 hours to obtain a sintered body close to the theoretical density.

Example 4 Instead of 40.738 g of lead nitrate [Pb (No ₃ ) ₂ ] in Example 1, 36.433 g of lead nitrate [Pb (No ₃ ) ₂ and strontium nitrate [Sr (No
₃ ) ₂ ] 2.751 g and the hydrothermal temperature was changed from 150 ° C. to 200 ° C., and the same operation as in Example 1 was carried out.

The obtained particle size was 0.2 μm or less, which was well uniform. When this powder was molded and fired at 800 ° C. for 2 hours, a sintered body close to the theoretical density was obtained.

Example 5 2 [Pb _1/2 Ca _1/2 (Zn _1/3 Nb _2/3 ] -3 [Pb (Cu _1/2 W _1/2 ))
O ₃ ] −95 [Pb _1/2 Nb _1/2 ) O _{3 In} Example 1, lead nitrate [Pb _1/2
b (No ₃ ) ₂ ] 40.738g instead of lead nitrate [Pb (No ₃ ) ₂ ] 40.33g
And the calcium nitrate _{[Ca (No 3) 2 ·} 4H 2 O] 0.290g, zinc nitrate _{[Zn (No 3) 2 ·} 6H 2 O] 0.244g, niobium hydroxide _{[Nb (OH) 5] 10.686g} , nitrate copper _{[Cu (No 3) 2 ·} 3H 2 O] 0.4
46 g, tungsten oxide [WO ₃ ] 0.428 g and iron nitrate [Fe
_{(No 3) 3 · 9H 2} O] except that the addition of 23.595g was operated in the same manner as in Example 1.

The obtained particle size was 0.2 μm and the particle size was relatively uniform.

When 0.6% of polyvinyl alcohol was added to this powder and formed, it was baked at 810 ° C for 2 hours, and the density was 8.45 g.
/ cm ³ and close to the theoretical density, 60 ° C. than when produced by a dry process
It could be fired at a low firing temperature.

[Effect of the Invention] According to the present invention, in the production of the perovskite raw material powder,
By contacting each solution and / or each suspension of the compound containing the constituent element of the perovskite with the precipitation-forming solution, the precipitation of each component is successively produced, and then hydrothermal treatment is performed to obtain fine particles (sub It is possible to reproducibly produce a uniform raw material powder of easily sinterable perovskite having a narrow particle size distribution. Further, according to the present invention, there is a feature that a sintered body having a lower firing temperature and good dispersibility can be obtained as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the perovskite raw material powder obtained in Example 1.

Claims (1)

[Claims] 1. A general formula X [A (B _a W _b ) O ₃ ] -y [A (B _c Nb _d ) O.
₃ ] (However, A represents at least one element selected from Pb, Ba, Sr and Ca, B represents at least one element selected from Mg, Zn, Ni, Co, Cu, Fe and Mn, a,
b, c and d are values determined by the valence of each of the above elements,
x and y represent mol% and x + y = 100. In the production of the raw material powder of the perovskite structure compound represented by the formula (4) and its solid solution (hereinafter referred to as perovskite), each solution and / or each suspension of the compound containing the above-mentioned constituent elements is brought into contact with a precipitation forming liquid. A method for producing a perovskite raw material powder, which comprises successively producing a precipitate of each component in a stepwise manner, and then subjecting the slurry containing the precipitate to a pH of 8.0 or more and performing a hydrothermal treatment at 130 to 300 ° C.