JPH0648734A - Production of crystalline titanic acid based perovskite-type fine particle - Google Patents

Abstract

PURPOSE:To obtain the subject fine particles by mixing a Ba compound or an Sr compound in a solution state with a Ti compound in a solution state or a slurry state at a temperature higher than starting temperature of the reaction. CONSTITUTION:As raw material compounds, hydroxides, oxides, salts, alkoxides of Ti and Ba or Sr, preferably hydroxides thereof are used. The Ba compound and the Sr compound may be used ringly or jointly. The atom ratio of Ba or Sr to Ti in mixing is 1.0-50 and the initial concentration of the reaction of Ba or Sr is 0.3-3.5mol/kg water. The mixing temperature is 60-120 deg.C and as the mixing means, an inline mixer is preferably used. The reaction time is preferably normally about 30min to 5hr, though the reaction time is not especially limited. By this reaction, the object fine particles having <=0.05mum average particle diameter and narrow particle size distribution is obtained. Furthermore, a coprecipitate obtained by dissolving a salt of rare-earth element (e.g. Y or La) in an aqueous solution of titanium salt and hydrolyzing them may be added to the reactional system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine particles of crystalline titanate-based perovskite compound, which is preferably used as a material for electronic parts such as dielectrics and piezoelectrics.

[0002]

2. Description of the Related Art Heretofore, the following methods (1) to (4) have been adopted for producing fine particles of a crystalline perovskite titanate compound such as barium titanate, strontium titanate and barium strontium titanate.

A solid-state reaction method in which a mixture of barium or strontium carbonate or oxide and titanium oxide is heated at high temperature. By reacting the salt of each component element with oxalic acid,
Oxalic acid method in which each oxalate is co-precipitated and heated at high temperature. An alkoxide method in which alkoxides of each component element are mixed and hydrolyzed. Hydrothermal synthesis method in which hydroxides of each element are mixed and hydrothermally reacted in a solution.

[0004]

However, the solid-phase reaction method and the oxalic acid method described above require a step of firing at a high temperature, and since viscous growth and fusion between particles occur during the high-temperature firing, It is difficult to obtain fine particles having an average particle diameter of less than 1 μm, that is, so-called submicron-sized fine particles, and the obtained particles have a crushed shape, resulting in poor filling properties.

Further, in the above alkoxide method, since the raw material alkoxide is expensive, it is economically disadvantageous for industrial application.

Therefore, by adopting the hydrothermal synthesis method as described above and performing hydrothermal reaction in an autoclave at 120 to 300 ° C., the average particle diameter is 1 μm or less and 0.01 μm.
It has been proposed to obtain fine particles of the above submicron size (JP-A-61-31345).

However, in the method described in the above publication, in the hydrothermal reaction for synthesizing the perovskite compound represented by the general formula ABO ₃ (where A is barium or strontium and B is titanium),
A method of mixing the hydroxide of the group A component element with the hydroxide of the group B component element, particularly the mixing temperature has not been sufficiently examined, and an expensive pressure vessel such as an autoclave must be used. There was a problem.

[0008]

The present inventors have manufactured crystalline titanate-based perovskite compound fine particles having a base material composition represented by (Ba _1-x Sr _x ) TiO ₃ (0 ≦ x ≦ 1). In doing so, by mixing the barium compound or strontium compound in a solution state and the titanium compound in a solution state or a slurry state at a temperature at which the reaction starts or more, the average particle size is 0.05 μm or less, and the particle size distribution is The inventors have found that narrow crystalline titanate-based perovskite compound fine particles can be obtained, and have completed the present invention.

That is, according to the present invention, the crystalline titanate-based perovskite compound fine particles having a base material composition represented by (Ba _1-x Sr _x ) Ti ₃ O (0 ≦ x ≦ 1) are produced by a wet reaction. By mixing a barium compound or strontium compound in a solution state and a titanium compound in a solution state or a slurry state at a temperature above the temperature at which the reaction starts, the concentration gradient and temperature distribution in the reaction system are made uniform, and instantly. By allowing the reaction to proceed, it is possible to prevent non-uniform agglomeration of fine particles to be produced, and to make the average particle diameter 0.0
It was made possible to obtain crystalline titanate-based perovskite compound fine particles having a particle size distribution of 5 μm or less and a narrow particle size distribution.

The starting compounds used in the present invention and the reaction conditions adopted will be described in detail below.

The raw material compounds usable in the present invention include hydroxides, oxides, salts and alkoxides of titanium and barium or strontium.

[0012] In particular, hydroxide is less contaminated with impurities, and titanium hydroxide is water-insoluble, which is convenient for controlling the particle size and particle size distribution of the obtained product. It is preferable to use an oxide.

That is, the particle size and particle size distribution of titanium hydroxide affect the particle size and particle size distribution of the obtained product, and by controlling the particle size and particle size distribution of this titanium hydroxide, Since the particle size and particle size distribution of the product can be controlled, it is preferable to use a hydroxide in controlling the particle size and particle size distribution of the resulting crystalline titanate-based perovskite compound particles.

As the titanium hydroxide, it is preferable to use those obtained by hydrolyzing titanium salts such as titanium chloride and titanium sulfate, and organic titanium such as titanium alkoxide, filtering and washing with water.

That is, in the titanium hydroxide obtained by the above-mentioned hydrolysis, the particle size and the particle size distribution can be controlled depending on the conditions at the time of the hydrolysis, so that the obtained crystalline titanate-based perovskite is obtained. This is because it helps control the particle size and particle size distribution of the compound particles.

Examples of barium hydroxide include barium hydroxide and barium hydroxide octahydrate, and examples of strontium hydroxide include strontium hydroxide and strontium hydroxide octahydrate. Are used.

These hydroxides, barium compounds and strontium compounds may be used alone or in combination.

As described above, in the case of using barium hydroxide or strontium hydroxide, if they remain in a solid state, even if they are mixed even at the reaction starting temperature or more, even if they are uniformly mixed. Since the dissolution equilibrium of barium hydroxide and strontium hydroxide is an endothermic equilibrium, a local temperature drop may occur, which may adversely affect the particle size distribution and particle size (particularly atomization) of the obtained product.

Therefore, the water-soluble hydroxides such as barium hydroxide and strontium hydroxide are completely dissolved, and the water-insoluble hydroxides of titanium hydroxide are uniformly slurried. Therefore, it is preferable to mix both.

When a titanium alkoxide is used as a raw material compound, the titanium alkoxide may be made into an alcohol solution and directly mixed with an aqueous solution of a barium compound or an aqueous solution of a strontium compound for reaction.

Further, when titanium hydroxide is obtained by hydrolysis of titanium salt, the salt of the semiconducting element is dissolved in an aqueous solution of titanium salt, and the coprecipitate obtained by hydrolysis is dissolved into a barium compound or It may be used for the reaction with the strontium compound.

The semiconducting element that can be used is (Ba
_{In the} perovskite type crystal structure represented by _1-x Sr _x ) TiO ₃ , a trivalent or pentavalent element which is semiconductive by substituting an atom of Ba, Sr or Ti, for example,
Rare earth elements such as Y, La, Ce, Pr and Nd, Nb and S
At least one selected from the group consisting of elements such as b, Ta, Bi, B, and W can be given.

The amount of these semiconducting elements added is
(Ba _1-x Sr _x ) TiO ₃ is appropriately contained in the range necessary to cause semiconductivity by being contained in 0.05 to 2 atomic% with respect to titanium. is there.

Therefore, not only barium titanate, strontium titanate, and barium strontium titanate can be used as the titanate-based perovskite compound in the present invention, but a part of them can be used as a base material for semiconductivity as described above. Those substituted with elements are also included.

Next, the reaction conditions adopted in the present invention will be described in detail.

In the present invention, it is preferable to employ a normal pressure heating reaction method as the wet reaction. That is, according to the present invention, since the reaction can proceed without requiring pressurization as in the conventional case, when the atmospheric pressure heating reaction method that can be carried out under atmospheric pressure is adopted as the reaction mode, its characteristics are Particularly remarkable. However, it is also possible to adopt the hydrothermal pressure method.

The above-mentioned normal temperature heating reaction method means that the reaction proceeds in a mixed aqueous solution or slurry of each component element compound.
It means a method of heating reaction under H (usually pH 10 or more) under normal pressure.

The temperature at which the reaction starts is the minimum temperature at which the X-ray diffraction peak of the crystalline titanate perovskite compound can be detected by the reaction aging within 3 hours in the above-mentioned wet reaction, that is, about 5 with respect to the raw material. % Refers to the lowest temperature at which a crystalline titanate-based perovskite compound is formed. For example, in the case of barium titanate, it is usually about 50 ° C., although there are some differences depending on the reaction conditions.

In the present invention, as a mixing means of the barium compound or strontium compound and the titanium compound, each compound in a solution state or a slurry state fed by a liquid feeding device such as a pump is placed in a reaction vessel equipped with a stirrer. Automatically drop, mix in liquid transfer line,
A method such as mixing with an in-line mixer can be adopted, but in order to achieve instantaneous and uniform mixing, it is preferable to use an in-line mixer.

In the present invention, the factors affecting the particle size of the crystalline titanate-based perovskite compound particles obtained are as follows:

(1) Mixing temperature (2) Atomic ratio of barium or strontium to titanium when starting materials are mixed (3) Initial reaction concentration of barium or strontium, etc.

The above-mentioned mixing temperature is the temperature at which the solution-state barium compound or strontium compound is mixed with the solution-state or slurry-state titanium compound. In the present invention, this temperature is several hours. Aged
Since the wet reaction is completed, the mixing temperature usually means the reaction temperature.

However, when the reaction is not completed only by aging for several hours at the above temperature, the reaction may be completed by raising the temperature after aging.

The mixing temperature is usually 60 ° C. or higher at which the reaction can proceed smoothly. The higher the mixing temperature, that is, the reaction temperature, the higher the reaction rate and the smaller the particle size of the product.
Above 0 ° C., this tendency disappears and grain growth begins.

Therefore, the preferable mixing temperature is 6
The range of 0 to 120 ° C. is preferable, and in order to shorten the reaction time, simplify the equipment, and better achieve atomization of the product, the temperature is preferably 80 ° C. or higher and lower than the boiling point of the mixed slurry at normal pressure.

Further, in order to obtain fine particles of crystalline titanic acid-based perovskite compound having an average particle size of 0.01 μm or less in the atmospheric pressure heating reaction method, it is preferable to mix at the boiling point of the slurry and then to reflux and age.

Upon mixing, the aqueous solution of barium compound, the aqueous solution of strontium compound, and the aqueous solution or slurry of titanium compound are preferably kept at the same temperature or higher than the mixing temperature.

As the atomic ratio of barium or strontium to titanium (A / B atomic ratio, where A is barium or strontium and B is titanium) when the raw material compounds are mixed, no unreacted titanium compound remains. Such a ratio is preferable, and if too much barium compound is added, a side reaction may occur and it is not economically preferable.

Therefore, the A / B atomic ratio is 1.0 to 50.
In order to further improve the reactivity and obtain crystalline titanate-based perovskite compound fine particles having an average particle diameter of 0.03 μm or less, the A / B atomic ratio is 1.2 to 5
The range of 0 is preferable, and the average particle diameter is 0.01 μm.
In order to obtain the following crystalline titanate-based perovskite compound fine particles, the A / B atomic ratio is preferably in the range of 3.0 to 50.

However, when a strong alkali such as sodium hydroxide or potassium hydroxide for improving the reactivity may be allowed to coexist, for example, even if the A / B atomic ratio is 1.0, the above-mentioned strong Coexistence of alkali makes it possible to obtain fine particles having a smaller particle size.

The initial reaction concentration of barium or strontium is preferably 0.3 to 3.5 mol / kg water. When the initial reaction concentration is lower than 0.3 mol / kg water, the reaction does not proceed smoothly, the dispersibility of the product is deteriorated, and only aggregated particles are obtained. The initial reaction concentration is 3.
When it is higher than 5 mol / kg water, the solubility of barium hydroxide or strontium hydroxide in water is limited and the reaction becomes difficult to proceed, which is not preferable.

The reactivity is further improved and the average particle size is 0.0
In order to obtain crystalline titanate-based perovskite compound fine particles having a particle size of 3 μm or less, the initial reaction concentration of barium or strontium is preferably 0.5 to 3.5 mol / kg of water, and the average particle size is 0.01 μm or less. In order to obtain the crystalline titanate-based perovskite compound fine particles, the initial reaction concentration of barium or strontium is preferably in the range of 1.5 to 3.5 mol / kg water.

The particle size of the crystalline titanate-based perovskite compound fine particles obtained in the present invention is higher as the mixing temperature is higher and the A / B atomic ratio at the time of mixing the raw material compounds is higher.
The higher the initial reaction concentration of barium or strontium, the smaller the tendency tends to be. Therefore, it is possible to control the average particle size of the obtained crystalline titanic acid-based perovskite compound particles to an arbitrary particle size within the range of 0.01 to 0.05 μm by setting the reaction conditions in consideration of these. it can.

The setting of reaction conditions is complicated because the above three factors interact with each other, but when expressed numerically from the viewpoint of reaction rate, the reaction rate is 9 hours or less within 3 hours.
By setting the system so as to reach about 5%, it is possible to obtain crystalline titanate-based perovskite compound fine particles having an average particle diameter of 0.05 μm or less.

The reaction time is not particularly limited as long as it is sufficient to complete the reaction under the above conditions, but is usually 30.
Minutes to 5 hours is preferable.

After the reaction was completed under the above conditions, the obtained product was filtered, washed with water, dried and calcined according to a conventional method to give a crystalline titanic acid-based perovskite compound in a fine powder state. Fine particles are obtained.

[0047]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to only those examples. In the following,% indicating concentration is% by weight unless otherwise specified.

Example 1 Titanium tetrachloride aqueous solution (containing 16.4% of titanium)
2.86 kg was added to 11.5 kg of pure water and stirred for 1 hour. 10.0 kg of 5% ammonia water in this aqueous solution
Was added dropwise to obtain a white slurry having a pH of 7.8.

The slurry was filtered, washed with water, reslurried, and heated to 60 ° C., acetic acid was added to adjust the pH.
Aged for 40 minutes at 6.0. After aging, filtration and washing with water gave a cake of hydrous titanium hydroxide gel having a solid content of 11%.

Cake 2 of the obtained hydrous titanium hydroxide gel
14 g of pure water in 74 g (containing 0.38 mol of titanium)
0 g was added and boiled, and 100% of barita water (barium hydroxide aqueous solution) with a concentration of 30% prepared and boiled in a nitrogen atmosphere was kept at 100 ° C. After mixing through the in-line mixer, the mixture was refluxed for 4 hours for aging.
After aging, the slurry was filtered, washed with water, and dried.

The product obtained as described above was confirmed by analysis by X-ray diffraction to be crystalline barium titanate, and the average particle diameter observed by an electron microscope was 0.01 μm. It was

FIG. 1 is an X-ray diffraction diagram showing the crystal structure of barium titanate produced in Example 1. As shown in FIG. 1, diffraction by the (110) plane, (111) plane, and (200) plane, which is a characteristic of barium titanate, at 2θ = 31.0 °, 38.0 °, and 44.5 °. A peak is recognized, and it can be seen that the product obtained in this Example 1 is barium titanate.

FIG. 2 is an electron micrograph showing the particle structure of barium titanate produced in Example 1 at a magnification of 300,000. As shown in FIG. 2, barium titanate produced according to Example 1 is ultrafine particles dispersed in primary particle units, and the average particle size thereof is 0.0 as described above.
It was 1 μm.

Comparative Example 1 Cake 545 of hydrous titanium hydroxide gel similar to that of Example 1
430 g of pure water in g (containing 0.75 mol of titanium)
284 g of barium hydroxide octahydrate (containing 0.90 mol as a barium content) was added to the slurry prepared by adding the above in a nitrogen atmosphere at room temperature (20 ° C.).

This slurry was charged into an autoclave and heated to 150 ° C. for 90 minutes while stirring to 150 ° C.
It was hydrothermally treated at 4 ° C. for 4 hours. After the reaction, the slurry was filtered, washed with water and dried.

The product obtained as described above was confirmed by analysis by X-ray diffraction to be crystalline barium titanate, but the average particle size observed by an electron microscope was 0.06 μm. Met.

FIG. 3 is an electron micrograph at 150,000 times showing the particle structure of barium titanate produced in Comparative Example 1. Although the magnification in FIG. 3 is 1/2 of that in FIG. 2, the barium titanate produced in Comparative Example 1 is the barium titanate produced in Example 1 even if such a difference in magnification is ignored. The particle size was larger, and the average particle size was 0.06 μm as described above.

Comparative Example 2 Cake 545 of hydrous titanium hydroxide gel similar to that of Example 1
430 g of pure water in g (containing 0.75 mol of titanium)
284 g (containing 0.90 mol as a barium content) of barium hydroxide octahydrate was added to the slurry which had been boiled after the addition of and was refluxed for 4 hours. After the reflux, the slurry was filtered, washed with water and dried.

The product obtained as described above was confirmed by analysis by X-ray diffraction to be crystalline barium titanate, but the average particle diameter observed by an electron microscope was 0.07 μm. Met.

Examples 2 to 12 and Comparative Examples 3 to 5 Examples were carried out except that the Ba / Ti atomic ratio, the initial concentration of barium reaction, the mixing temperature, the reaction time, and the like when the starting compounds were mixed were changed. The reaction was carried out in the same manner as in 1.

Table 1 shows the reaction conditions in each Example and Comparative Example, the average particle size of the obtained barium titanate observed by an electron microscope, and the presence or absence of crystallinity as judged from the analysis by X-ray diffraction. Table 1 also shows the cases of Example 1 and Comparative Examples 1 and 2. Regarding the comparative example, the above items are shown in a simplified manner.

[0062]

[Table 1]

* 1 A mixed slurry of hydrous titanium hydroxide and barium hydroxide prepared at room temperature and hydrothermally treated. * 2 Barium hydroxide octahydrate added to boiling slurry of hydrous titanium hydroxide and refluxed.

As is clear from the values shown in Table 1, the higher the Ba / Ti atomic ratio at the time of mixing the raw material compounds, the higher the barium reaction initial concentration, and the higher the mixing temperature, the more titanic acid obtained. The average particle size of barium tends to be small, and the average particle size of barium titanate produced is controlled to 0.0 by controlling the reaction conditions.
It can be seen that it is possible to control arbitrarily within the range of 5 to 0.005 μm.

Examples 1 to 12 and Comparative Examples 1 to 5
Number particle size distribution of barium titanate produced in Example 8 and Comparative Example 1 (the number of extracted particles = 3,000)
Is shown in FIGS. 4 and 5.

As shown in FIG. 4, most of the barium titanate produced in Example 8 had a particle size of 0.02 to 0.02.
Although it was within the range of 0.04 μm, as shown in FIG. 5, the barium titanate produced in Comparative Example 1 had a particle size distribution in a wide range of 0.02 μm to 0.10 μm.

As is clear from FIGS. 4 and 5, barium titanate obtained by the present invention is fine particles and has a narrow particle size distribution width.

Example 13 The reaction was carried out under the same conditions as in Example 1 except that the reaction time was changed, and the relationship between the amount of barium titanate produced and the reaction time was examined. The result is shown in FIG. The amount of barium titanate produced was calculated from the peak area of the (110) plane by X-ray diffraction.

As shown in FIG. 6, in the case of Example 13, the reaction time was about 20 minutes, and the production amount of barium titanate reached almost 100%, indicating that the reaction proceeded very rapidly. Recognize.

Further, when the barium titanate produced when the reaction time was 30 minutes and 5 hours was observed by an electron micrograph, both had an average particle diameter of 0.01 μm, and even if the reaction time was as short as 30 minutes, the objective The fine particles to be obtained were obtained.

Example 14 The reaction was carried out under the same conditions as in Example 9 except that the reaction time was changed. As in Example 13, the relationship between the amount of barium titanate produced and the reaction time was shown. Examined. The results are shown in FIG. 6 together with the case of Example 13. The method for calculating the amount of barium titanate produced is the same as in Example 13.

As shown in FIG. 6, in the case of Example 14, the reaction time was about 4 hours, and the production amount of barium titanate reached almost 100%.
It can be seen that the reaction rate decreases as the Ti atomic ratio and the initial reaction concentration of barium decrease.

That is, in Example 13, the Ba / Ti atomic ratio was 4.5, and the initial reaction concentration of barium was 1.7 mol.
In Example 14, the Ba / Ti atomic ratio is 1.2, and the initial reaction concentration of barium is 0.43 m.
It was ol / kg water, which was lower than that of Example 13, and as a result, the reaction rate decreased as described above.

When barium titanate produced when the reaction time was 5 hours was observed by an electron micrograph, the average particle diameter was 0.03 μm.

Comparative Example 6 The reaction was carried out under the same conditions as in Comparative Example 3 except that the reaction time was changed, and in the same manner as in Example 13, the relationship between the amount of barium titanate produced and the reaction time was shown. Examined. The results are shown in FIG. 6 together with the cases of Examples 13 to 14. The method for calculating the amount of barium titanate produced is the same as in Example 13.

As shown in FIG. 6, in the case of Comparative Example 6, even if the reaction time exceeded 5 hours, the amount of barium titanate produced was only about 95%, and the reaction rate was slow.

Further, when barium titanate produced when the reaction time was 5 hours was observed by an electron micrograph, the average particle diameter was 0.2 μm, and it was found that the reaction rate slowed down as described above. It can be seen that the obtained barium titanate particles are aggregates of primary particles.

Example 15 Hydrous titanium hydroxide gel cake 274 similar to that of Example 1
104 g of pure water per g (containing 0.38 mol of titanium)
Was added and boiled, and 1034 g of a strontium hydroxide aqueous solution having a concentration of 20% prepared and boiled under a nitrogen atmosphere (containing 1.7 mol as a strontium content) was kept at 100 ° C in-line. After mixing through a mixer, the mixture was refluxed for 4 hours for aging. After aging, the slurry was filtered, washed with water, and dried.

The product obtained as described above was confirmed by analysis by X-ray diffraction to be crystalline strontium titanate, and the average particle diameter observed by an electron microscope was 0.01 μm. It was

Examples 16 to 21 The reaction was carried out in the same manner as in Example 15 except that the conditions such as the Sr / Ti atomic ratio when the raw material compounds were mixed, the initial reaction concentration of strontium, and the mixing temperature were changed.

Table 2 shows the reaction conditions in each example, the average particle diameter of the obtained strontium titanate observed by an electron microscope, and the presence or absence of crystallinity determined by the analysis by X-ray diffraction.

[0082]

[Table 2]

As is clear from the values shown in Table 2, the higher the Sr / Ti atomic ratio when the raw material compounds are mixed, the higher the initial concentration of strontium in the reaction, and the higher the mixing temperature, the more titanic acid obtained. The average particle size of strontium tends to be small, and by controlling these reaction conditions, the average particle size of the produced strontium titanate can be arbitrarily controlled between 0.05 and 0.005 μm. I know there is.

Example 22 Hydrous titanium hydroxide gel cake 274 similar to that of Example 1
104 g of pure water per g (containing 0.38 mol of titanium)
Was added and boiled, and 984 g of a barium hydroxide-strontium hydroxide aqueous solution having a concentration of 28% prepared and boiled under a nitrogen atmosphere (1.3 barium content was used).
6 mol and 0.34 mol as strontium content) were mixed through an in-line mixer kept at 100 ° C. and then refluxed for 4 hours for aging. After aging,
The slurry was filtered, washed with water, and dried.

The product obtained as described above was confirmed to be crystalline barium strontium titanate as a result of X-ray diffraction analysis, and the Ba / Sr atom was measured as a result of fluorescent X-ray diffraction measurement. Since the ratio was 4.0, it was confirmed that the rational formula was Ba _0.8 Sr _0.2 TiO ₃ . Furthermore, the average particle size observed by an electron microscope was 0.01 μm.

Examples 23 to 29 Reactions were carried out in the same manner as in Example 22 except that the conditions such as (Ba + Sr) / Ti atomic ratio at the time of mixing the raw material compounds, the initial reaction concentration of barium and strontium, and the mixing temperature were changed. I went.

Table 3 shows the reaction conditions in each example, the average particle size of the obtained barium strontium titanate observed by an electron microscope, and the presence or absence of crystallinity determined by the analysis by X-ray diffraction. Table 3 also shows the case of the twenty-second embodiment.

[0088]

[Table 3]

As is clear from the values shown in Table 3, even in the case of barium strontium titanate, the reaction conditions such as the (Ba + Sr) / Ti atomic ratio at the time of mixing the raw material compounds, the initial reaction concentration of barium and strontium, and the mixing temperature. The average particle size of the produced barium strontium titanate is controlled to 0.05 to 0.005 by controlling
It is understood that it is possible to control arbitrarily within μm.

Example 29 Titanium tetrachloride aqueous solution (containing 16.4% of titanium)
2.86 kg was added to 11.5 kg of pure water, and an aqueous solution of niobium pentachloride in hydrochloric acid (containing 3.5% of niobium) 5
3 g was added and stirred for 1 hour. To this aqueous solution, 10.0 kg of 5% ammonia water was added dropwise to obtain a white slurry having a pH of 7.7.

The slurry was filtered and washed with water, then reslurried, and then heated to 60 ° C., acetic acid was added to adjust the pH.
Aged for 40 minutes at 6.0. After aging, it was filtered and washed with water to obtain a cake of hydrous titanium hydroxide gel containing 0.2 atom% of niobium and having a solid content of 11.4%.

264 g of the obtained niobium-containing hydrous titanium hydroxide gel cake (containing 0.38 mol of titanium)
Slurry boiled after adding 104 g of pure water to boiled water and barita water with a concentration of 30% prepared in a nitrogen atmosphere and boiled 9
71 g (containing 1.7 mol as a barium component) and 10
After mixing through an in-line mixer kept at 0 ° C, the mixture was refluxed for 4 hours for aging. After aging, the slurry was filtered, washed with water, and dried.

The product obtained as described above was confirmed to be crystalline barium titanate as a result of X-ray diffraction analysis, and was also measured as a result of ICP (inductively coupled plasma) emission analysis. It was confirmed that the content rate of niobium was 0.2 atomic%. Furthermore, the average particle size observed by an electron microscope was 0.01 μm.

Examples 30 to 33 Reactions were carried out in the same manner as in Example 29 except that the Ba / Ti atomic ratio at the time of mixing the raw material compounds, the initial reaction concentration of barium, the mixing temperature and other conditions were changed.

Table 4 shows the reaction conditions in each example, the average particle size of the obtained niobium-containing barium titanate observed by an electron microscope, and the presence or absence of crystallinity determined by analysis by X-ray diffraction. Table 4 also shows the case of Example 29.

[0096]

[Table 4]

As is clear from the values shown in Table 4, even when a semiconducting agent such as niobium was added, the Ba / Ti atomic ratio at the time of mixing the raw material compounds, the initial reaction concentration of barium, the mixing temperature, etc. By controlling the reaction conditions,
It is understood that it is possible to arbitrarily control the average particle diameter of the niobium-containing barium titanate to be produced within the range of 0.05 to 0.005 μm.

[0098]

According to the present invention, a barium compound or strontium compound in a solution state and a titanium compound in a solution state or a slurry state are mixed at a temperature not lower than the temperature at which the reaction is started, whereby the concentration gradient in the reaction system is increased. By making the temperature distribution uniform and making the reaction proceed instantaneously, it becomes possible to produce crystalline titanate-based perovskite compound fine particles having an average particle size of 0.05 μm or less and a narrow particle size distribution.

Further, according to the present invention, all of the starting materials are compounds that can be stably supplied, and since no expensive equipment such as an autoclave is required in the manufacturing process, a very simple line can be used. It can be manufactured.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram showing a crystal structure of barium titanate produced according to Example 1 of the present invention.

FIG. 2 is an electron micrograph showing the particle structure of barium titanate produced according to Example 1 of the present invention at a magnification of 300,000.

3 is an electron micrograph at 150,000 times showing the particle structure of barium titanate produced in Comparative Example 1. FIG.

FIG. 4 is a graph showing the number particle size distribution of barium titanate produced in Example 8.

5 is a graph showing the number particle size distribution of barium titanate produced in Comparative Example 1. FIG.

6 is a graph showing the relationship between the production amount of barium titanate and the reaction time in Examples 13, 14 and Comparative Example 6. FIG.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Osamu Kobayashi 1-3-47 Funamachi, Taisho-ku, Osaka

Claims (6)

[Claims] 1. A crystalline titanic acid having a base material composition represented by (Ba _1-X Sr _X ) TiO ₃ (0 ≦ x ≦ 1) by wet-reacting a barium compound or a strontium compound with a titanium compound. In producing the perovskite-based compound fine particles, a crystalline titanate-based perovskite characterized by mixing a barium compound or strontium compound in a solution state and a titanium compound in a solution state or a slurry state at a temperature at which the reaction starts or higher. Method for producing compound fine particles. 2. The barium compound is a hydroxide or oxide of barium, the strontium compound is a hydroxide or oxide of strontium, and the titanium compound is a hydroxide or oxide of titanium. The method for producing fine particles of crystalline titanic acid-based perovskite compound according to claim 1. 3. The mixing temperature is 60 to 120 ° C., the atomic ratio of barium or strontium to titanium during mixing is 1.0 to 50, and the initial reaction concentration of barium or strontium is 0.3 to 3.5 mol. 2. The method for producing crystalline titanic acid-based perovskite compound particles according to claim 1, wherein the average particle size of the crystalline titanic acid-based perovskite compound particles obtained is 0.05 μm or less. 4. The mixing temperature is 80 to 120 ° C., the atomic ratio of barium or strontium to titanium at the time of mixing is 1.2 to 50, and the initial reaction concentration of barium or strontium is 0.5 to 3.5 mol. 2. The method for producing crystalline titanate-based perovskite compound fine particles according to claim 1, wherein the average particle diameter of the crystalline titanate-based perovskite compound fine particles obtained is 0.03 μm or less. 5. The mixing temperature is 100 to 120 ° C., the atomic ratio of barium or strontium to titanium during mixing is 3.0 to 50, and the initial reaction concentration of barium or strontium is 1.5 to 3.5 mol. 2. The method for producing crystalline titanic acid-based perovskite compound fine particles according to claim 1, wherein the average particle diameter of the resulting crystalline titanic acid-based perovskite compound fine particles is 0.01 μm or less. 6. The method for producing crystalline titanate-based perovskite compound fine particles according to claim 1, wherein the mixing means is an in-line mixer.