JPH01122907A - Production of perovskite oxide powder - Google Patents

Abstract

PURPOSE:To efficiently produce the above powder having excellent quality at a low cost, by dispersing a specific metallic oxide in water or an organic solvent, adding a solution of a precipitate-forming agent and soluble metallic compound to the resultant dispersion and calcining the obtained precipitates. CONSTITUTION:A metallic oxide, consisting of amorphous fine particulate oxide (e.g., TiO2) having <=0.1mum particle diameter and insoluble in water or organic solvent is dispersed in water or an organic solvent so as to provide 1-1,000g/l concentration of the metallic oxide. A soluble of a precipitate-forming agent (e.g., NaOH) in an equiv. amount-10 times based on the above-mentioned oxide and a soluble metallic compound [e.g., Pb(NO3)2] containing a metallic element other than the afore-mentioned element in 0.005-10mol./l concentration is added to stir the resultant dispersion at >=0 deg.C for <=200hr and form precipitates. The obtained precipitates are then separated by filtration, washed, dried at 50-200 deg.C for 1-200hr and subsequently, calcined at 400-1,200 deg.C for 0.5-100hr in an oxidizing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a method for producing herovskite oxide powder. More specifically, the present invention 1i,
The present invention relates to a method for efficiently producing perovskite oxide powder, which is suitably used as a raw material for functional ceramics such as piezoelectrics, dielectrics, semiconductors, sensors, and optoelectronic materials, by firing at a relatively low temperature.

[Prior Art] Perovskite oxides have the general formula ABO3 (where A
is a 12-coordinated metal element of oxygen, and B is a 6-coordinated metal element of oxygen.
It is known to have optical effect properties, and these properties can be used to create piezoelectric and dielectric materials such as filters, ultrasonic vibrators, and resonators, as well as optoelectronic materials such as optical shutters and optical memories. are widely used as functional ceramics such as semiconductors and sensors.

Recently, components using such functional ceramics have become smaller and their applications have become more diverse, and therefore there is a demand for raw material powders that are excellent in quality, easy to sinter, and low in cost.

Conventionally, the method for manufacturing perovskite oxide powder is as follows:
Dry methods and wet methods are known. The former dry method is a method in which constituent raw material compounds (mainly oxides) are mixed using a ball mill or the like, and then fired at a high temperature.

However, with this method, it is difficult to obtain perovskite oxide powder with a uniform composition, and since the raw material compound is fired at a high temperature, the resulting powder inevitably becomes coarse, and sufficient sinterability cannot be obtained. There are drawbacks.

On the other hand, known wet methods include an alkoxide method, a coprecipitation method, and a powder dispersion precipitation method. In the alkoxide method, after mixing the constituent alkoxides of various metals,
This is a method of adding water to hydrolyze and then calcining the hydrolyzate (Japanese Unexamined Patent Publication No. 57-8Z120). However, in this method, the raw material alkoxide is extremely expensive. In addition to the inevitable increase in manufacturing costs, there are problems such as being dangerous to operate and causing large dimensional shrinkage due to sintering.

In addition, the coprecipitation method is a method in which a mixed solution containing all the constituent components is prepared, a precipitate is added to this to obtain a coprecipitate, and this coprecipitate is then dried and fired. Since the precipitate-forming ability of each component is not constant, it is difficult to obtain the desired composition, and the particles may coagulate during precipitate formation, drying, or calcination to form secondary particles. It has drawbacks such as being difficult to form and sintering easily.

Furthermore, in the powder dispersion precipitation method, a metal compound that is substantially insoluble in water or alcohol is dispersed in the solvent, and a solution containing a soluble metal compound containing metal elements other than those mentioned above is added to the dispersion to form a precipitate. This method involves adding a perovskite oxide powder with a perovskite oxide powder to obtain a precipitate, which is then fired, and is easy to sinter, has a low manufacturing cost, and can obtain a perovskite oxide powder that is uniform and has a high bulk density. , has attracted attention as a superior method compared to the above-mentioned methods (Japanese Patent Application Laid-Open No. 1983-
163118), however, in the conventional powder dispersion precipitation method, ・Since a crystalline metal compound is used as a metal compound that is substantially insoluble in water or alcohol, high temperatures are required for firing. This method was not necessarily completely satisfactory.

[Problems to be Solved by the Invention] The present invention improves the drawbacks of the conventional method for producing perovskite oxide powder, and produces perovskite oxide powder that is easy to sinter and has excellent quality. This was done with the aim of providing a method of manufacturing efficiently at low cost and at a low firing temperature.

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors found that in the powder dispersion precipitation method, metals that are substantially insoluble in water or organic solvents The inventors have discovered that by using amorphous fine particles of metal oxide as the compound, the firing temperature can be lowered, thereby achieving the objective, and based on this knowledge, the present invention has been completed.

That is, in the present invention, a metal oxide substantially insoluble in water or an organic solvent is dispersed in the solvent, and then a precipitant and a soluble metal containing a metal element other than the above are added to the dispersion. A perovskite characterized in that an amorphous fine particle oxide is used as the metal oxide in producing a perovskite oxide powder by adding a solution containing a compound to form a precipitate and then firing the precipitate. A method for producing oxide powder is provided.

The present invention will be explained in detail below.

The perovskite oxide powder obtained by the method of the present invention is represented by the general formula: A B Os ...N) (in the formula, A is a 12-coordination metal element of oxygen, and B is a 6-coordination metal element of oxygen). It is a metal oxide powder with a perovskite structure.

Examples of the oxygen 12-coordination metal element of the A component in the general formula (1) include Pb, Ba, Ca, Sr, and L.
Examples include rare earth elements such as a. The A component may contain one type of these metal elements,
Two or more types may be contained. Further, as the oxygen hexacoordination metal element of the B component, for example, Ti, Zr, HH, S
c, Hf, Tb, Il, Nb, Ta, Cr,
No, Mn, Fe, Co, Ni, Zn, Cd,
^1. Examples include Sn, ^s, Bi, etc. The B component may contain one type of these metal elements, or may contain two or more types of these metal elements.

The combination of two or more elements of the B component in the perovskite oxide is a combination of equivalent elements such as the combination of Ti'' and Zr'°, and the combination of ( The same applies to the case of the A component), and for example, 1/
2 Fe” and 1/2 Nb”, 2/3 Fe3+ and 1
/3 W”, 1/2 Hg”° and 2/3 Nb”
Furthermore, it may have an excess or deficiency of charge at the position of the A component or the position of the B component, and these charges may be compensated for by the generation of cation defects and anion defects, for example. B component Ti4°+
Combination of H@+ (cation defect compensation), Ti'°
and ^13° (anion defect compensation), A component La'° and B
a” (cation defect compensation), etc. The perovskite oxide obtained by the present invention may be
It also includes non-stoichiometric ones in which the molar ratio of the A component and the B component is shifted to a value higher or lower than 1.0 to introduce holes at the B position or the A position.

In the method of the present invention, water or methanol,
A dispersion liquid is prepared by selecting a metal oxide that is substantially insoluble in an alcohol such as ethanol or an organic solvent such as acetone and dispersing it in the solvent, but it is possible to use an amorphous fine particle oxide as the metal oxide. is necessary. Examples of such materials include TiOx, Zr0t, N
Examples include b2O, Hg01Sn02, Ta205, and composite oxides thereof. These metal oxides are X-ray amorphous, and their particle size is usually 0.1 μm.
The following are preferably used. If a crystalline oxide is used as the metal oxide instead of such an amorphous fine particle oxide, the effect of lowering the firing temperature will not be obtained, and the object of the present invention will not be achieved.

In addition, the slurry concentration in the dispersion is 1 to 100.
A range of 0 g/l is preferable; if the concentration is less than 1 g/l, productivity will be low, and if it exceeds 1000 g/l, a product with a non-uniform composition will tend to be obtained, which is not preferable.

On the other hand, from among the compounds of perovskite constituents A and B, a soluble metallized food containing a metal element other than the metal element of the metal oxide is selected, and water or an organic solvent such as alcohol such as methanol or ethanol or acetone is used. Prepare a solution by dissolving it in Examples of the soluble metal compound include pb, Zr, La, Sr, Ba, Ca,
Examples include nitrates such as Hg, chlorides, alkoxides, and organic acid salts. Among these metal compounds, those that are easily decomposed during the firing process and do not easily leave anionic groups are preferred, such as nitrates and alkoxides.

In addition, the concentration of the metal compound in the solution is 0.005
The range of ~10 mol/1 is preferable, and this concentration is 0.00
If it is 505 mol/1, the productivity is low, and if it exceeds 10 mol/1, a product with a non-uniform composition is likely to be obtained, which is not preferable.

Examples of the precipitating agent used in the present invention include alkalis such as ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate, and organic acids such as oxalic acid and citric acid. Examples include acids. Among these precipitating agents, those that are easily decomposed during the firing process and are difficult to remain are preferred, such as ammonia and oxalic acid. These precipitants are usually used in the form of an aqueous solution, and the amount used is preferably selected from an equivalent to 10 times the amount.

In the method of the present invention, a precipitate is added to a dispersion containing a metal oxide prepared as described above, and a solution containing a soluble metal compound is added to form a precipitate. There is no particular restriction on the order in which the soluble metal compound-containing solution is added; for example, the precipitant may be added to the dispersion, and then the soluble metal compound-containing solution may be added, or the dispersion may first be added with the soluble metal compound-containing solution. The soluble metal compound-containing solution may be added and then the precipitate forming agent may be added. Note that the addition is preferably carried out while stirring the liquid.

The formation of the precipitate is usually carried out at a temperature ranging from 0° C. to the boiling point, and the formation time is usually sufficient within 200 hours.

Further, in the present invention, precipitation can also be formed in multiple stages. For example, after forming a precipitate of a certain component,
In order to remove anions that would interfere with subsequent steps, the precipitate is removed by means such as filtration, and then the precipitate containing the amorphous fine particle oxide is dispersed in fresh water or an organic solvent, and then in this dispersion, a precipitant,
A solution containing the remaining metal components may be added to form a precipitate. Furthermore, when forming a precipitate in multiple stages in a dispersion containing the same amorphous fine particle oxide, after forming a certain precipitate, The type and concentration of the precipitant may be appropriately selected and adjusted to be suitable for forming a precipitate of the remaining components.

Next, the precipitate thus formed is thoroughly washed with water or an organic solvent to remove attached anions, filtered, dried, and fired. Drying is
1 to 20 at a temperature usually in the range of 50 to 100°C.
The firing is preferably carried out in an oxidizing atmosphere, for example in air, at a temperature usually in the range of 400 to 1200°C for about 0.5 to 100 hours. If the calcination temperature is too low, the solid phase reaction rate will be slow; if the calcination temperature is too high, particle growth may occur. On the other hand, if the calcination time is too short, no solid phase reaction occurs, and if the calcination time is too long, particle growth tends to occur.

In the present invention, trace components can be added as desired in order to control the sinterability and properties of the perovskite. This trace component may be added when preparing a dispersion or solution of the component, or
Further, after the perovskite oxide powder is produced, it may be added to the powder in a dry or wet manner.

[Effects of the Invention] According to the method of the present invention, in the production of perovskite oxide powder by the powder dispersion precipitation method, when preparing a dispersion of a metal oxide that is substantially insoluble in water or an organic solvent, the metal oxide is By using amorphous fine particle oxide, the firing temperature can be lowered compared to conventional methods, which is economically advantageous.

The perovskite oxide powder obtained by the method of the present invention has excellent characteristics such as easy sinterability, uniform composition, and high bulk density.
It is suitably used as a raw material for functional ceramics such as semiconductors, sensors, and optoelectronic materials.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

(1) Production of lead zirconate titanate (PZT) powder (Example 1) TiJ36, which is X-ray amorphous and has an average particle size of 0.02 μm, produced by the method described in JP-A-61-201604.
．． 75 g was dispersed in 0.5N ammonia water 101 (liquid A> was prepared).

On the other hand, lead nitrate 321.2. and zirconium oxynitrate 2
Water salt 144.3. 61 in ion-exchanged water, (B
) solution was prepared. Next, while stirring liquid A at room temperature,
Solution (B) was added at a rate of 0.5//win, and after the addition was completed, stirring was continued for an additional hour.

This slurry was washed with water, filtered, and dried at 120°C overnight, and then the dried product was calcined at 500 to 900°C for 2 hours to obtain lead zirconate titanate powder. The crystal phase of this product was identified by X-ray diffraction. FIG. 1 shows the X-ray diffraction pattern of the fired product at each firing temperature.

In addition, in the figure (here, ma is the diffraction peak of PZT.

(Comparative Examples 1 to 4) In Example 1, instead of amorphous TiO2, rutile type particles with an average particle size of 0.3 μm (Comparative Example 1) and 0.05 μm were used.
m (Comparative Example 2), 0.0:bzm (Comparative Example 3)
Lead zirconate titanate powder was obtained in the same manner as in Example 1, except that TiO2 of 0.0158 m (Comparative Example 4) was used.

The X-ray diffraction patterns are shown in FIGS. 2 to 5.

As is clear from Figures 1 to 5, when X-ray amorphous Ti0z is used, the temperature is 200°C lower (700°C) than in Toya using crystalline Ti12. A single phase lead zirconate titanate is formed.

(2) Production of lead titanate (PT) powder (Example 2) Ti0279 that is X-ray amorphous and has an average particle size of 0.02 μm produced by the method described in JP-A-61-201604.
．． 90g of Shu M138.8. ethanol containing 1
01 to prepare solution (C). On the other hand, lead nitrate 3
24.6° and 4.723 g of calcium nitrate tetrahydrate were dissolved in a mixed solvent 61 of ethanol/water (50150') to prepare solution (D).

Next, while stirring the solution (C) at room temperature, add the solution (D) to 0.
．． The mixture was added at a rate of 517w1n, and stirring was continued for an additional hour after the addition was complete. This slurry was washed with water, filtered,
After drying at ℃ overnight, dry the dried product at 500-900℃ for 2 hours.
Calcinate for an hour to obtain lead titanate powder.

The crystal phase of this product was identified by X-ray diffraction.

Note that calcium nitrate tetrahydrate is an additive for improving the piezoelectric properties of lead titanate.

(Comparative Example 5.6) Rutile-type average particle size 0.3 μm (Comparative Example 5), 0.03
Example 2 except that Tie of μm (Comparative Example 6) was used.
A fired product was obtained in the same manner as above. Furthermore, the crystal phase of the fired product was identified by X-ray diffraction.

From the comparison between Example 2 and Comparative Examples 5 and 6, when using X-ray amorphous TiO A single phase of lead titanate was formed.

(3) Production of PZT powder Tie2, which is X-ray amorphous and has an average particle size of 0.03 μm, was produced by the method described in JP-A-61-201604.
/Zr0z (45/55 molar ratio) 103.73F
I was dispersed in 0.5N ammonia water 51, and (A
) solution was prepared. On the other hand, lead nitrate 331.2. was dissolved in ion-exchanged water of No. 21 to prepare solution (B).

At room temperature, while stirring liquid (A), liquid (B) was heated to 0.
The mixture was added at a rate of 31/sin, and stirring was continued for an additional hour after the addition was completed. This slurry was washed with water, filtered, and heated to 120°C.
After drying overnight, the dried product was calcined at 500 to 900°C for 2 hours to obtain PZT powder. The crystal phases of these were identified by X-ray diffraction.

From the comparison between Example 3 and Comparative Examples 1 to 4, when X-ray amorphous TiO□/ZrO2 is used, crystalline TiO
Single-phase lead zirconate titanate was produced at a temperature about 200°C lower (680°C) than when using z.

[Brief explanation of the drawing]

Figure 1 shows the X-ray diffraction patterns of the fired product at each firing temperature in Example 1, and Figures 2, 3, 4 and 5.
The figures are X-ray diffraction patterns of the fired products at each firing temperature of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, respectively. In each figure, the square indicates the diffraction peak of PZT.

Claims (1)

[Claims] (1) After dispersing a metal oxide that is substantially insoluble in water or an organic solvent, this dispersion contains a precipitant and a soluble metal compound containing a metal element other than the above. A perovskite oxide powder, characterized in that an amorphous fine particle oxide is used as the metal oxide in producing the perovskite oxide powder by adding a solution of manufacturing method.