JPS6052092B2 - Manufacturing method of perovskite-type lead-containing composite oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a perovskite-type lead-containing composite oxide, and more specifically, the present invention relates to a method for producing a perovskite-type lead-containing composite oxide, and more specifically, it relates to a method for producing a perovskite-type lead-containing composite oxide, and more specifically, a method for producing a perovskite-type lead-containing composite oxide.
Alternatively, the present invention relates to an improvement in a method for producing the above composite oxide by a hydrothermal reaction with hydrated zirconium acid.

In particular, the present invention relates to a method for producing a perovskite-type lead-containing composite oxide that has a high degree of crystallinity into a perovskite structure and has an excellent degree of pulverization, and is useful as a ceramic raw material. Lead titanate, lead zirconate, and lead zirconate titanate having a perovskite crystal structure are widely used in fields such as dielectric ceramics, piezoelectric ceramics, pyroelectric ceramics, resistor ceramics, and semiconductor ceramics.

The most common manufacturing method for synthesizing such lead-containing double oxides is the so-called oxide method, in which a lead oxide component and a titanium dioxide component are subjected to a solid phase reaction at high temperatures. However, when the product obtained by such a solid phase reaction is subjected to X-ray diffraction, in addition to the X-ray diffraction image peculiar to lead titanate, the It shows a line diffraction pattern and has the disadvantage of being extremely heterogeneous in composition. For this reason, in the case of composite oxides obtained by solid phase reaction, the complicated and expensive operations of pulverizing the product and calcining it again must be repeated. Furthermore, the double oxide obtained by this solid phase reaction method has a coarse particle size and lacks intimate miscibility with other raw materials and auxiliary raw materials due to the fact that it has been subjected to a thermal history at high temperatures. It also has the disadvantage of poor reactivity. In order to improve the above-mentioned drawbacks of the solid phase reaction method, it is already known to produce lead titanate by a solution method.

A typical method is to react titanyl nitrate, etc. with a water-soluble lead salt such as lead nitrate or lead acetate in an aqueous medium containing oxalic acid, as described in U.S. Patent No. 335,263. The method consists of forming an oxalate salt and thermally decomposing the complex oxalate at a temperature of 700° C. or higher to obtain lead titanate. This method has the disadvantage that when producing lead titanate, particle growth is promoted by heating at a high temperature of 700° C. or higher, resulting in coarsening and non-uniformity of the particle size of the target product. In addition, the special public service
In the publication, hydrogen peroxide is added to a solution containing a water-soluble titanium salt such as titanium tetrachloride or titanium nitrate, and a water-soluble lead salt such as lead nitrate, and an alkali such as ammonia is added. It is disclosed that a composite peroxide is precipitated by maintaining the pH at 3 or higher, and the composite peroxide is hydrolyzed at a temperature of 100° C. or higher to produce amorphous lead titanate.

This method achieves the advantage of obtaining relatively homogeneous amorphous lead titanate at relatively low temperatures, which amorphous lead titanate has a very porous gel morphology. It is still not fully satisfactory for use as a raw material for ceramics. stomach.

In other words, in order to make lead titanate into a ceramic, it is necessary to form a molded body in which lead titanate particles are densely packed, and for this purpose, lead titanate must be fine particles. , according to the oxide method mentioned above. The above-mentioned requirements are difficult to meet because those produced by the solution method tend to aggregate to form coarse particles even if the primary particle size is fine, and the grindability is poor.

Furthermore, all known lead titanate raw materials have the disadvantage that significant grain growth occurs during sintering into ceramics, and this grain growth destroys the compact.

Thus, in the production of conventional lead titanate ceramics, oxides such as manganese, zinc, lanthanum, etc. are blended as grain growth inhibitors to suppress the above-mentioned grain growth. The present inventors have discovered that when lead monoxide and hydrated titanic acid or hydrated zirconium acid are dispersed in an aqueous medium and subjected to a hydrothermal reaction with stirring, fine particle sizes and relatively large ratios can be obtained. A lead-containing composite oxide such as lead titanate having a surface area and a fine perovskite crystal structure can be obtained, and in this case, the degree of hydration is 1 or more and j is 7 or more as hydrated titanate or hydrated zirconium acid. By using small hydrated particles, it is possible to obtain a complex metal oxide that has a high degree of crystallinity into a perovskite structure and has excellent powderability, making it particularly useful as a raw material for sintering into ceramics. I found out.

According to the present invention, lead monoxide and at least one hydrate selected from the group consisting of hydrated titanic acid and hydrated zirconium acid are dispersed in an aqueous medium and subjected to a hydrothermal reaction with stirring. The method for producing perovskite-type lead titanate is characterized by using a fine hydrated hydrated titanic acid or hydrated zirconic acid having a degree of hydration of 1 or more and less than 7. A method is provided.

In the present invention, lead monoxide and at least one of hydrated titanic acid and hydrated zirconic acid react under hydrothermal conditions,
To provide a perovskite-type microcrystalline lead-containing composite oxide, and in this case, if a relatively small hydration degree of 1 or more and less than 7 is used as hydrated titanic acid or hydrated zirconium acid, crystallization will occur. This is based on the new knowledge that a remarkable improvement in the degree of oxidation and the degree of pulverization can be achieved.

Conventionally, in order to form a perovskite-type lead-containing composite oxide such as lead titanate, a crystallization temperature of 550° C. or higher has generally been required.

In other words, in the oxide method, lead monoxide and titanium oxide are heated at 600°C.
At the above temperature, a solid phase reaction occurs and at the same time crystallization into a perovskite crystal structure progresses. In addition, in the solution method, once formed amorphous lead titanate or lead titanate precursor is
It transforms to a perovskite crystal structure at a temperature of 50°C or higher. In contrast, in the present invention, lead monoxide, which is normally insoluble in water, and hydrated titanic acid or hydrated zirconium acid having a specific degree of hydration are mixed under hydrothermal conditions at a temperature of 110 to 200°C. It reacts at a relatively low temperature and provides a lead-containing composite oxide in the form of perovskite crystals.

In the present invention, the importance of hydrothermally reacting both raw materials will become clear by referring to the X-ray diffraction image shown in FIG. 1 of the accompanying drawings.

In FIG. 1, curve 1-A is the X-ray diffraction image of the starting raw material mixture, namely a mixture of lead monoxide and hydrated titanic acid, and curve 1-B is the X-ray diffraction image of the starting material mixture, i.e., a mixture of lead monoxide and hydrated titanic acid, and curve 1-B is the
curve 1-C is 1 atm (gauge) and curve 1-C is 1 atm (gauge).
-D is 2.5 atm (gauge), curve 1 is at 3.5 atm (gauge), and curve 1-F is at 4.5 atm (gauge). Show the image. Referring to these X-ray diffraction images, at a pressure and temperature as low as 1 atm, the X-ray diffraction peak characteristic of lead monoxide in the raw material mixture disappears, and at a pressure of 2.5 atm or higher, perovskite-type titanic acid Lead begins to form, and further 4.5
It is understood that under atmospheric pressure hydrothermal conditions (145 is C), the production of perovskite-type lead titanate is remarkable.
Furthermore, in the present invention, the importance of using hydrated titanic acid or hydrated zirconium acid having a degree of hydration of 1 or more and less than 7, particularly in the range of 3 to 6, is explained below. This will become clear by referring to Table 1.

That is, Table 1 below shows the pressure of 4.5 atm (gauge) when hydrated titanic acid with a hydration degree of 5.2 and hydrated titanic acid with a hydration degree of 7.5 are used as raw materials. A hydrothermally synthesized product under the conditions of 0.0. The apparent crystallinity (relative value) and crystallite size (values in brackets in Table 1) are shown for fired products obtained by time firing. Here, the crystallinity (%) is the diffraction peak of the plane index [101] plane of perovskite lead titanate (CuKα20=
31.40), and the size of the crystallite is also expressed as the thickness of the crystal (apparent crystal size) of the plane index [101) plane using the Scherrer formula described later.
DOOl) (AO). According to the results in Table 1 above, by using hydrated titanic acid whose degree of hydration is within the range specified by the present invention, the crystallinity of lead titanate produced by hydrothermal synthesis can be significantly improved. It can be seen that the degree of crystallinity of the fired product can be significantly improved.

This applies not only to hydrated titanic acid but also to the case where hydrated zirconic acid is used. As described above, the perovskite type composite oxide according to the present invention has the advantage of having a high degree of crystallinity and having little strain between crystallites.

Because of this characteristic, this composite metal oxide is less likely to condense even when subjected to thermal history such as firing, and has excellent powdering properties.This fact can be seen in the examples described below. It will become immediately obvious. In the present invention, lead monoxide used as one of the raw materials is a basic substance as shown by its aqueous suspension pH of 9.5 to 10.8.

The other raw materials, hydrated titanic acid and hydrated zirconium acid, are acids as obvious from their names, and thus the reaction in the present invention can be said to be a solid-phase acid-mono-alkali reaction under hydrothermal conditions. In the present invention, the hydrated titanic acid or hydrated leuconic acid used as a raw material is a formula in which M represents Ti or Zr, and n is a number greater than or equal to 1 and less than 7, particularly a number from 3 to 6. It is.

).

Here, the degree of hydration n is determined by the method described in Examples below. The above-mentioned hydrated titanic acid with a low degree of hydration can be obtained by the following method, although it is not limited thereto. That is, an aqueous slurry of an aqueous solution of a titanium salt such as titanium nitrate, titanyl sulfate, or titanium heptachloride and a heated hydrolysis product of an aqueous solution of titanium nitrate or titanyl sulfate is neutralized with ammonia at a high temperature, and hydrated titanic acid is prepared at a high temperature. Precipitate as a precipitate. In this case, the degree of hydration of hydrated titanic acid changes depending on the temperature at which the precipitate is precipitated; as the temperature increases, the degree of hydration decreases, and as the temperature decreases, the degree of hydration increases. Tend. In the present invention, the degree of hydration can be kept within the above range by adjusting the temperature during precipitation of hydrated titanic acid within the range of 60 to 98°C, particularly 70 to 85°C. When producing hydrated titanic acid, other points to be noted are that neutralization is performed so that the particle size of the hydrated titanic acid particles produced is 2 microns or less, especially 1 micron or less; The objective is to precipitate hydrated titanic acid particles in a state with good filterability.

That is, when the particle size of hydrated titanic acid is large, the reactivity with lead monoxide tends to be low, and the degree of crystallinity to form a perovskite-type composite oxide tends to be low. In addition, if the filtration properties of hydrated titanic acid are poor, it will be difficult to thoroughly remove contaminant ions, and the presence of such contaminant ions will cause the perovskite complex oxide to crystallize during hydrothermal synthesis. In addition, when the composite oxide is fired, it tends to agglomerate, which tends to significantly worsen the pulverization rate. As described above, in the production of hydrated titanic acid, there are contradictory demands to make the particles finer and to improve their filterability.

These contradictory demands can be met by rapidly stirring the mixture of the titanium salt solution and ammonia water within a range that satisfies the ammonia water addition time constant shown in Table 2 below.
You can be satisfied at the same time. That is, by mixing under rapid stirring, the hydrated titanic acid produced has a fine particle size, but
Furthermore, the particle size distribution becomes uniform, which results in good filterability. Any other hydrated titanic acid? Factors that affect the transient nature include the temperature during neutralization, the salt concentration in the reaction system, etc. That is, the higher the neutralization temperature, the better the filterability, and the higher the concentration of water-soluble salts present in the reaction system, the better the p-permeability of hydrated titanic acid obtained. In the present invention, the overload resistance is 0.4Tn. /Hr or more, especially 0.77TL/Hr
It is desirable to use the above hydrated titanic acid. The resulting hydrated titanic acid is thoroughly washed with water and used in hydrothermal synthesis in the form of a wet cake or aqueous slurry. Ru.

In the present invention, the hydrated zirconic acid used as a raw material is obtained in exactly the same manner as the hydrated titanic acid, except that an aqueous solution of zirconium oxychloride is used.

As the other raw material, lead monoxide, either a dry method or a wet method can be used. This lead monoxide may have a so-called surge type or mashikotsu type crystal structure, or may have a hydrous lead monoxide crystal structure. The lead monoxide produced by the dry method has a particle size of 1 to 1.
Particles in the range of 0 μm are suitable, but especially if the particle size is 7 μm.
When using lead monoxide classified to be less than μm,
A perovskite-type lead-containing composite oxide is obtained which is particularly suitable for use as a ceramic base. In the method of the present invention, it is particularly desirable to use lead monoxide produced by a wet method.

This wet process lead monoxide is 8.3 to 9.2y/C as described in U.S. Pat. No. 4,117,104.
True density of c, primary particle size less than 0.2 microns, wave number 1
Infrared absorption peak from 400 to 14100-1, and 9
It has a chromic anhydride reaction rate of 4% or more, and is excellent in fine particle size and reactivity. This lead monoxide raw material is produced by filling a rotating mill with granular metal lead, a liquid medium, and oxygen gas; at least a part of the granular metal lead moistened with the liquid medium is lower than the surface of the liquid medium The rotary mill is rotated under conditions in which the particles of lead metal are exposed to the upper gas phase and the particles of lead metal rub against each other in the liquid medium, whereby the ultrafine particles of lead oxide are exposed to the liquid medium. It is produced by forming a dispersion in which the metal lead is dispersed; separating said dispersion from the granules of metallic lead, and optionally recovering the lead monoxide formed from said dispersion in the form of a fine powder. The lead monoxide raw material and hydrated titanic acid or hydrated zirconium acid are
The reaction is carried out in an amount ratio capable of forming a perovskite type complex oxide, that is, in a substantially equimolar amount.

At this time, a part of the lead monoxide raw material, especially an amount of 20 mol% or less, is added to metal components such as calcium, magnesium, barium, strontium, lanthanium, etc. within the range that perovskite type composite oxide is formed. hydroxide can be used as a substitute, and a part of the titanic acid or zirconic acid raw material, especially an amount of 20 mol% or less, can be used as a substitute for manganic acid, niobic acid, tungstic acid, iridic acid, etc. be able to. According to the present invention, the above-mentioned raw materials are dispersed in an aqueous medium and a hydrothermal reaction is performed while stirring. The concentration of the raw materials to be dispersed in the aqueous medium is not particularly limited, but from the viewpoint of ease of stirring and capacity of the reactor, a range of 5 to 4 weight percent is appropriate. The hydrothermal reaction is
Aqueous dispersions of both raw materials were supplied into a pressure vessel and heated to 1000C.
temperature, particularly from 110 to 200°C, most preferably from 120 to 150'C. If the temperature is lower than the above-mentioned temperature, perovskite crystals will not be formed effectively, and if the temperature is too high, there will be no particular advantage, and the pressure will increase on the contrary, so it is advantageous to set the reaction temperature to 200°C or less. It is. The pressure during the reaction is the autogenous pressure of water, but if desired, it may be pressurized with air, nitrogen, etc. In the present invention, it is extremely important to stir the aqueous dispersion of both raw materials during this hydrothermal reaction. If stirring is not performed, the reaction will be non-uniform, resulting in the formation of perovskite crystals. rate decreases.

The reaction time varies somewhat depending on the type of raw material, but generally a relatively short time of about 3 to 5 hours is sufficient.

The reaction can be carried out either in a Baltic or continuous manner; in the former case, for example, an autoclave with a stirrer is used, and in the latter case, a vibrator continuous reactor with stirring blades or multiple distribution plates is used. can do.

Thus, according to the present invention, it is possible to directly form a lead-containing composite oxide consisting of perovskite-type microcrystals with extremely fine grain size, large specific surface area, and high crystallinity through a hydrothermal reaction. can.

Moreover, according to the present invention, the raw materials used are entirely composed of reactive components such as lead monoxide and titanic acid and/or zirconic acid, and do not contain any soluble ions such as alkali metal ions, ammonium ions, and acid ions. This has the advantage that it is possible to prevent the product from being contaminated with these ions and that there is no need for any purification operations such as washing. The obtained composite oxide is dried if necessary,
Alternatively, it can be fired at a temperature of up to 850°C and used for various purposes.

The microcrystalline perovskite-type lead-containing composite oxide according to the present invention has several novel features compared to those conventionally used as ceramic bases.

That is, the lead-containing composite oxide according to the present invention substantially consists of perovskite-type microcrystals having a composition represented by the following formula, where M represents Tl and Zr,
The half width of the strongest diffraction line in the CU-KaX single-line diffraction peak is 0.30 degrees or more at the diffraction angle Δ(2θ), and has a primary particle size of 0.5 microns or less and a BET specific surface area of 5 i/y or more. ing.

Figures 2-A and 2-B of the attached drawings are X-ray diffraction images of microcrystalline lead titanate, a lead-containing composite oxide according to the present invention,
The (2-A) figure shows the dried product at 120℃ and (2-B)
The figure shows an X-ray diffraction image of the calcined material at 750°C.

From this X-ray diffraction image, it is understood that the lead-containing composite oxide according to the present invention has a perovskite crystal structure. Generally, the finer the crystallites, the lower the height of the X-line diffraction peak, and the half-width Δ(20
) is known to increase. Therefore, the lead-containing composite oxide according to the present invention has a half-width Δ
The fact that (20) is greater than 0.30 degrees indicates that the crystallites are extremely fine although the crystals are quite developed. Furthermore, it is believed that the lead-containing composite oxide according to the present invention contains almost no amorphous composite oxide and is substantially entirely composed of perovskite-type microcrystals.

That is, the titanium-lead composite oxide system according to the conventional method has a
Whereas lead titanate as obtained by hydrothermal synthesis according to the present invention shows an exothermic peak at 520'C due to crystallization, such an exothermic peak is not observed at all, and the crystallites are almost It is understood that it is fully formed. These facts are explained in the third section, which shows the relationship between the crystallite size and the calcination temperature, which will be described later using the Scherrer equation.
As shown in the figure, the following can be understood from the degree of crystal development at each plane index when microcrystalline lead titanate powder is exposed to various temperatures.

That is, in the lead-containing composite oxide according to the present invention, the perovskite-type crystallization reaction is substantially completed, whereas in the conventional method, no crystal development is generally observed at temperatures below 500°C. , especially in the method of the present invention, 5
It is well understood that crystal growth progresses sequentially even at temperatures below 00°C. The lead-containing composite oxide as obtained by the hydrothermal reaction has a half-width Δ(20) of 0.7 degrees or more at the diffraction peak.

Moreover, according to a scanning electron micrograph of the lead-containing composite oxide according to the present invention, the lead-containing composite oxide according to the present invention has the above-mentioned perovskite type microcrystals, and has a particle size of 0.5 microns or less. BET ratio surface is 5 i/
It has the characteristic of being at least V, especially at least 10 d/V.

With known methods, it is extremely difficult to obtain perovskite-type oxides with particle sizes smaller than 1 micron, and even if they are amorphous or have a relatively large specific surface in the case of precursors, perovskite-type oxides cannot be obtained. When converted into a type crystal,
Its specific surface area is much smaller than 5i/f.
On the other hand, the lead-containing composite oxide according to the present invention has a remarkable feature that, although it is a crystal, it has a large specific surface area of 5Tr1/y or more, particularly 10w1/y or more.
Since the lead-containing composite oxide according to the present invention has the above-mentioned properties, it exhibits unexpected and remarkable effects when used in the production of ceramics.

First of all, this composite oxide has a fine primary particle size and high surface activity, so it exists in the form of secondary particles in which the primary particles are softly aggregated. It can be easily formed into a ceramic structure of a desired shape by the following means. Moreover, this lead-containing composite oxide has a fine primary particle size, high surface activity, and has a perovskite-type crystal structure.
It can be sintered at a low temperature of 1000° C. to 1000° C., and a perovskite ceramic body that is dense and has excellent mechanical strength can be formed by sintering at such a low temperature. The ceramic body formed from the lead-containing composite oxide according to the present invention has a density of 96% to 98.5% of the theoretical density. Furthermore, the lead-containing composite oxide according to the present invention has the above-mentioned excellent sintering properties and can be sintered at low temperatures, so grain growth during sintering is significantly suppressed, such as A perovskite ceramic body with excellent properties can be obtained without adding a grain growth inhibitor. Although the lead-containing composite oxide according to the present invention is a perovskite crystal, it has fine particle size and high surface activity, and can be used for applications other than ceramics, such as exhaust gas purification catalysts and electrode catalysts. It can also be advantageously used in such fields.

The invention is illustrated by the following example.

Example Lead monoxide and finely divided hydrated titanic acid and hydrated zirconium acid having a specified degree of hydration are dispersed in an aqueous medium,
A method for producing an ultrafine-crystalline perovskite-type lead-containing composite oxide that maintains unique physical properties through a hydrothermal reaction under stirring and its physical properties will be explained.

Raw materials for hydrated titanic acid include titanium nitric acid solutions prepared by the methods described in JP-A-54-54914 and JP-A-54-80297, and commercially available titanium sulfate and titanium tetrachloride acids. The solution and the aqueous slurry of heated hydrolysis products of titanium nitrate and titanium sulfate are each maintained under heating and stirring, and an ammonia aqueous solution is added thereto to form fine particles with a specified degree of hydration. We selected hydrated titanic acid.

The preparation conditions for the hydrated titanic acid selected here are as follows.
The properties are shown in Table 3.

The raw material hydrated zirconium acid is disclosed in JP-A-54-54914.
A nitric acid solution of zirconium prepared by the method described in the published patent application and an acid solution of zirconium oxychloride (ZrOCf2), a commercially available reagent, were mixed in a predetermined ratio into each of the titanium acid solutions described above, or a single solution was added, respectively. By keeping the mixture under warm stirring and adding an ammonia aqueous solution to it, we prepared hydrated zirconium acid, which has superior permeability similar to hydrated titanic acid and has a specified degree of hydration. is expressed as (Δ), and the hydrochloride system is expressed as (ZC),
The characteristics of each hydrated zirconium acid are shown in Table 4 below.

As the raw material lead monoxide, lead monoxide prepared by the wet mill method described in the specification of U.S. Patent No. 4117104 and lead monoxide prepared by the dry method described in the specification of Japanese Patent Publication No. 37-11801 were selected. .

The physical properties shown in Tables 1 to 4 were measured according to the following methods.

1) Edge resistance (m/Hr) The generated hydrated titanic acid and hydrated zirconium acid slurry are
O. Using 5A Okigami paper, filter with a porcelain filter with an inner diameter of 11cm at a reduced pressure of 500TW1Hg, and the filter cake thickness is approximately 2C77! It was defined as the linear velocity (m/Hr) of the deepwater liquid calculated from the filtration rate (d/Hr) of the offshore liquid per unit p overarea (a) when

2) Degree of hydration (n) The degree of hydration (n) in the MO-NH2O formula is the degree of vacuum 500T.
The ignition loss of the reduced pressure alcoholic cake in nInHg is expressed as MO
It is expressed and defined as the number of moles of water per number of moles.

3) Particle size (μm) Maximum particle size measured by microscopy, and magnesium (Mg) and calcium (Ca) as raw materials for other metal components coexisting in perovskite-type lead titanate or lead zirconate titanate. , barium (Ba),
Each nitrate of strontium (Sr), manganese (Mn), tungsten (W), indium (In), lanthanum (La), and niobium (Nb) was selected from commercially available reagents, and each was added to the specified amount ratio shown in Table 6. In advance, a solution of each titanium dissolved in an acid solution or a mixed acid solution of each titanium-zirconium or a single solution is maintained under heating and stirring, and an ammonia aqueous solution is poured into this. Fine particle hydrates of hydrated titanic acid or hydrated titanic acid zirconium acid with excellent p-porosity containing the desired metal components, and fine particle hydrates of the desired metal components, respectively. Prepared.

Each perovskite type lead titanate and lead zirconate titanate were produced according to the following method.

Table 5 lists the components in each sample as lead titanate component (PT), lead zirconate component (PZ), and composite perovskite component (P(B)) corresponding to each perovskite crystal composition.
1, B2)), and a lead titanate component ((PA)T) obtained by partially replacing the lead component of PT with another component. The manufacturing conditions can be arbitrarily selected within the range shown in Table 6.

As for the specific production method of perovskite-type lead-containing composite oxide, each of the above-mentioned fine particulate hydrates prepared according to the molar ratio of perovskite-type component species shown in Table 7 was ion-exchanged with 2e. Pour into a stainless steel container (inner volume: 5 f) with water and a stirrer, and let it stand for 5 minutes at room temperature without heating.
A homogeneous fine-grained hydrate slurry is prepared under high-speed stirring at 00 r'Pm or higher, while the lead monoxide slurry (L
W-1, LW-2, LW-3) or lead monoxide powder (
A lead monoxide slurry having a concentration of 400 f/e was prepared in advance by dispersing LD-1) in water.

Next, in a stainless steel stirring type autoclave with a steam jacket (inner volume: 5'), the above fine particulate hydrate slurry and lead monoxide slurry were mixed with stirring, heated to 145°C, and hydrothermally treated for 1 hour. Eleven kinds of reaction product slurries of lead-containing complex oxides of perovskite type crystals with excellent p-permeability were prepared by performing an interfacial solid phase reaction.

The product slurry thus obtained was then recovered as a cake by filtration, and then each was evaporated at the temperature shown in Table 7 to 0. Drying and calcining took a long time to obtain a fine powder type of each perovskite-type microcrystalline lead-containing composite oxide. In order to clarify the present invention, a lead-containing compound was prepared by the following method and used as a comparative example.

Comparative Example H-1: Based on the method described in the specification of Japanese Patent Publication No. 54-106514, the raw materials of lead oxide and titanium oxide powder (raw material number T-H1) were mixed by a wet pulverization method, and then PbO
/TiO2 in a molar ratio of 1 was calcined at the temperature shown in Table 7 to obtain perovskite-type lead titanate crystals.

Comparative Example H-2: Based on the method described in the specification of Japanese Patent Publication No. 54-18679, lead nitrate (raw material number P-H1) and titanium nitrate (raw material number T-H2) were used as raw materials, and further 10
Hydrogen peroxide equivalent to f8 molar amount and aqueous ammonia equivalent to equivalent molar amount were added to form an amorphous titanium and lead composite peroxide, and then dried at 150°C (sample number H). -2A) and a perovskite crystal material (sample number H-2B) calcined at 600°C.

Comparative Example H-3: Titanium hydrate (raw material number TN-5, T
N-6) was used as a titanium raw material, and subjected to hydrothermal treatment in an autoclave in the same manner as sample number 1-1 in the example, resulting in sample number (H-3A) and sample number (H-3B), respectively. did.

Comparative Example H-4: Fine particulate titanium hydrate (raw material number TN-1
), hydrothermal treatment in an autoclave using lead monoxide slurry (sample number LW-1) and zirconium hydroxide (raw material numbers ZC-3, ZC-4) in the same manner as in the case of sample numbers 1-10 in the example. were given sample numbers (H-4A) and sample numbers (H-4B), respectively.

Comparative Example H-5: U.S. Patent No. 335263? A composite oxalate is coprecipitated from ammonium oxalate or oxalic acid using lead nitric acid, titanium oxynitrate, and zirconium oxynitrate (raw material number Z-H1) as raw materials according to the method described in the specification, and the resulting coprecipitation The material was thermally decomposed at 850°C to form a perovskite crystal.

Comparative Example H-6: Raw materials include lead monoxide (raw material number LD-1) and hydrated titanium (raw material number TN-4) with a degree of hydration (n = 7.5).
) was subjected to hydrothermal treatment in an autoclave in the same manner as sample number 1-1 in the example, and the obtained lead titanate was designated as sample number (H-6).

The following physical properties were measured for each of the perovskite-type lead-containing composite oxide powders prepared here, and the results are also shown in Table 7.

In the table, the symbols used to represent the crystal forms are perovskite crystal (Cp), amorphous form (Am), and mixture other than Cp (Mx). Furthermore, from among the perovskite-type lead-containing composite oxide powders obtained here, one type was selected, and as an example of a specific application, in order to apply it to ferroelectric ceramics, it was molded by the following method and then The physical properties shown below were measured for the molded bodies sintered under the sintering conditions shown in the table, and the results are also shown in Table 8. The molding method uses approximately 1 piece of each lead-containing composite oxide powder (powder).
Uniaxial molding with a press pressure of 000k9/d,
Diameter 20W! 11 Pellets (molded bodies) having a thickness of 2 gourds were prepared.

1. Uniformity of composition by chemical analysis, 2. Particle size of powder and sintered body measured under a scanning electron microscope, crystal shape by 3X single-line diffraction, half-width of (101) plane, apparent crystallinity and Crystallite size, 4 Degree of pulverization, 5 Specific surface area of powder by BET method, 6 Bulk density of compacts and sintered bodies, 7 Hardness of sintered bodies, 8 Dielectric properties of sintered bodies 8 items Each was measured by the measurement method shown below.

1 Compositional homogeneity Approximately 2 f from 4 points each for each reaction product wet cake
A sample is collected, the Ti content is dissolved with ammonium sulfate and sulfuric acid, the Tl content is analyzed by a conventional metal A1 reduction method, and the Zr content is analyzed by a conventional EDTA method.

On the other hand, the Pb content is converted into PbSO4 precipitate, and after Okibetsu CH3C
Dissolve with OONH4 and analyze the Pb content using the conventional EDTM method. From this analysis value, calculate the molar ratio of PlO and TlO2, and from this molar ratio value, calculate the average deviation rate (%) of the molar ratio of each sample defined by the following three formulas, and use this value to determine the uniformity of the composition. was evaluated. ^-V-'Vζ-'14 2 Particle size of powder and sintered body The particle size of the dried and calcined powder of each sample and the particle size of the sintered body formed and sintered using these powders. The sintered particle size etc. were observed and measured under a scanning electron microscope and a metallurgical microscope.

Crystallinity and Crystallite Size by 3X One-Line Diffraction X-line diffraction was performed using the powder method on powder samples that had been dried and calcined after being held at a specified temperature for 0.2 hours to examine the crystal form of each sample and determine its CU. The relative value of the height of the diffraction line of the Miller index (101) plane was determined from -KαX one-line diffraction, and the apparent crystallinity of each sample was evaluated.

Further, X-line diffraction was performed using the Si (220) diffraction line as an internal standard according to Warren's method.

The width at half maximum (β) of all the detected diffraction lines (β) is corrected according to the following formula 1, and the following 2 formulas (Wllll
The crystallite size D (AO) was determined from the intercept obtained by plotting the relationship between 2sin0/λ and βCOsθ/λ in the two equations using the equation lamsOn.

Furthermore, when the lattice strain η = 0 can be considered in Equation 2,
Scherrer's equation 3 is obtained, and using this, the thickness of the crystal (apparent crystal size) Dhk at each plane index
I(AO) was calculated. β: Spreading of the diffraction line purely due to crystallite size and lattice strain (Rad) corrected using equation 1 θ: Bra angle λ: Wavelength of CLlKα line (AO) D: Crystallite size ( AO) η; Lattice strain 4 Degree of pulverization (Pw%) After drying each sample and crushing 20y of the calcined body in a mortar, it was sieved for 1 minute on a 200rT1eSh stainless steel sieve using a brush. The weight of the powder obtained (W)
The weight percent (50W) of the passing powder was calculated from y, and the degree of powderization was evaluated from the magnitude of this value.

5 Specific surface area by BET method The BET specific surface of each powder sample was measured for drying and calcined powder, and the surface activity of the powder on sintering was evaluated from the value as an example of the usefulness of each powder. .

6 Bulk density of compacts and sintered bodies After covering the surfaces of the compacts and sintered bodies of each powder sample with parine, the bulk densities (ρ) and (ρ
s) was measured, and then the density ratio (ρ/ρc<)) and sintering degree (ρs/ρ00) of each molded body were calculated and evaluated from the ratio with the theoretical density (ρ00) of each sample.

7 Hardness of the sintered body After polishing the surface of the sintered body well using sandpaper,
Load 5 using KASHI micro Vickers hardness tester
The hardness of the sintered body at 00y was measured.

Dielectric properties of 8 sintered bodies Each sintered body is 1T! After polishing to R1n thickness, EIK on both sides
A coating device made by O was used to evaporate A metal as an electrode, and a copper lead wire was attached using silver paste.

Next, using a vector impedance meter manufactured by HEWLET-PACKERD,
The dielectric constant, dielectric loss, Curie point, etc. were measured at a temperature range of 20 to 550°C. Furthermore, the resistivity of the sintered body was measured using a current measurement method in which a direct current of 1 KV was applied in silicone oil. As is clear from the above results, Tables 7 and 8,
Conventional general manufacturing methods for lead-containing composite oxides include the oxide method (sample number H-1A of Comparative Example-1) and the coprecipitation method (sample numbers H-2A and H-2B1 of Comparative Example-2). Sample number H-5 of Comparative Example-5 and sample number H-6 of Comparative Example-6) and Comparative Examples 3 and 4 used hydrated titanic acid and hydrated zirconium acid, which are unsuitable as raw materials for the present invention. It has been found that the production method of the present invention can produce a fine powder of a perovskite-type microcrystalline lead-containing composite oxide that retains unique physical properties that cannot be obtained by any production method including the comparative examples used. .

This is because the characteristics of the raw materials used in the present invention are that the generalized lead is finely granulated, and the titanium that is the M component in the HO/MO2 formula is finely hydrated titanic acid.
It is mainly composed of amorphous titanic acid, and it is also possible to produce lead-containing perovskite crystals consisting of components other than titanium and zirconium listed in Table 4, similar to fine-grained hydrated zirconium acid. Each fine-grained hydrate is
All of these are highly reactive raw materials with a degree of hydration (n) in the range of 1 to 7, and as a result, MO2/NH
This seems to be because the PbO component a and the MO2 component are active hydrated raw materials sufficient to contribute to the hydrothermal reaction as a solid base component and a solid acid component, respectively, while the 2O component undergoes dehydration.

Moreover, the production method of the present invention involves dispersing both of these components in an aqueous medium, and then causing an interfacial solid-phase reaction in which both components come into contact with each other under a hydrothermal reaction under stirring (see the X-ray diffraction diagram in Figure 1). reference)
Moreover, considering that the crystalline reaction products formed are sequentially peeled off and dispersed in the aqueous medium, and at the same time new similar reactions proceed one after another, solid-phase reactions do not occur under thermal history as in conventional methods. Since this is different from a reaction that continues to proceed in a fixed state and crystallizes all at once, it is also a feature of the present invention that the crystallite size obtained from the WiIIIamsOn formula of the reactant is obtained as extremely fine crystals of 400A0 or less. .

As shown in Table 6, the half width of the strongest diffraction line in the CU-Kα ) It is well understood that the value is larger than that of crystalline products, and it is also well understood that it is coarse because it eliminates the strong coagulation caused by hydrates that tends to be seen in amorphous dried products of conventional coprecipitation methods. A characteristic feature of the perovskite-type lead-containing composite oxide according to the present invention is that it has no visible grains and is highly pulverizable, so it easily turns into fine powder crystals even after thermal history. The crystalline material obtained by the invention includes:
There is no unreacted hydrate that condenses during drying, and the powder has a higher degree of pulverization (Pw) after drying depending on the degree of hydration (n) of the titanium raw material used. This indicates that the resulting reaction product is likely to consist of an almost anhydrous perovskite crystal, and therefore the solid phase reaction of the present invention proceeds completely.
This can be easily understood from the extremely high values of Mq, which indicates the homogeneity of the composition of the reactants, shown in Table 7. Furthermore, as is clear from Table 7 showing the physical properties of the molded body and the sintered body obtained using the fine powder of the perovskite-type microcrystalline lead-containing composite oxide obtained by the present invention, the moldability is high. Due to its density, high degree of sintering, fineness of sintered particles, high Vickers hardness, etc., the powder obtained by the present invention has extremely excellent formability, and by using this powder, extremely dense It is well understood that a sintered body with a high quality can be obtained.

This means that the powder obtained by the present invention is a perovskite-type lead-containing composite oxide with excellent sinterability that could not be produced by any conventional method, and that in the sintering process, Is it possible to create dense products at low temperatures of 1000℃ or less without using additives as grain growth inhibitors that are commonly used in the past? This is surprising and would not have been possible with powders produced using conventional methods.

More specifically, the calcined powder of a conventional oxide (Sample No. H-1A of Comparative Example 1) and the amorphous material (Sample No. H-2A) of the coprecipitation method (Comparative Example 12) and its temporary Burnt powder (sample number H-
2B) etc. and the powder of Example-1 (sample numbers 1-1, 1-2
, 1-3, 1-4, 1-5, and 1-6), it is clear from the results in Table 7, the X-ray diffraction diagram in FIG. 2, and FIG. Lead titanate consists of extremely fine crystal particles, and unlike conventional lead titanate powder, which undergoes a solid phase reaction for the first time under thermal history conditions and becomes completely crystalline at once, it is Figure 1 shows that the fine perovskite crystals are already fine crystals under the reaction conditions, and during the subsequent thermal history process, these fine perovskite crystals grow gradually and have not yet reached grain growth. It is well understood from the X-ray diffraction diagram and the half-width of its diffraction line peaks that, unlike any powder produced by conventional methods, the specific surface area of the powder is extremely small even in the calcination temperature range of 900°C or less. It is clear from Table 7 that this is high.

As is clear from the sintering results in Table 8, these powder characteristics are different from conventional lead titanate powders (Comparative Examples 1, 2, 3, 4,
It has almost no characteristics as a sinterable powder that are not found in 5 and 6).

[Brief explanation of drawings]

FIG. 1 shows a mixture of lead monoxide and hydrated titanic acid, and an X-ray diffraction image when the mixture is hydrothermally treated under predetermined conditions.
FIG. 2 is an X-ray diffraction image of microcrystalline lead titanate, a lead-containing composite oxide according to the present invention, and FIG. 3 is a diagram showing the relationship between crystallite size and calcination temperature.

Claims (1)

[Claims] 1. Lead monoxide and at least one hydrate selected from the group consisting of hydrated titanic acid and hydrated zirconium acid are dispersed in an aqueous medium and heated under stirring under hydrothermal treatment. A method for producing a perovskite-type lead-containing composite oxide comprising a reaction, characterized in that a fine particulate hydrate with a degree of hydration of 1 or more and less than 7 is used as hydrated titanic acid or hydrated zirconium acid. How to do it. 2. The method according to claim 1, wherein the hydrothermal reaction is carried out at a temperature of 110 to 200° C. and under autogenous pressure. 3. The method according to claim 1, wherein lead monoxide and the hydrate are reacted in substantially equimolar amounts. 4. The method of claim 1, wherein the lead monoxide is lead monoxide having a particle size of 0.01 to 10 microns. 5. The method according to claim 1, wherein the hydrated titanic acid or hydrated zirconium acid has a degree of hydration of 3 to 6. 6. The method according to claim 1, wherein the hydrated titanic acid or hydrated zirconic acid has a particle size of 2 microns or less. 7. The method according to claim 1, wherein the hydrated titanic acid or hydrated zirconic acid is amorphous.