JP3154509B2 - Barium titanate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to barium titanate and a method for producing the same.

[0002]

2. Description of the Related Art Barium titanate is used as a capacitor, PT
It is used as a dielectric material for electronic components such as C thermistors. Recently, barium titanate has been required to be able to control the particle size according to the purpose and to have high dispersibility. It has become.

For example, regarding a capacitor, in order to obtain a capacitor having a high dielectric constant and excellent temperature characteristics, niobium and cobalt are added to tetragonal barium titanate.
A so-called core-shell sintered body is obtained by changing the crystal structure of tetragonal barium titanate from the grain boundaries of the ceramic toward the inside of the grain, but in order to obtain a material having good characteristics, the particle size of the ceramic must be 0. It is necessary that the particle diameter is 5 to 1 μm and the particle diameter is uniform. In order to obtain such ceramics, barium titanate as a raw material is required to have a particle size of 0.5 to 1 μm and a narrow particle size distribution.

In a high dielectric constant type multilayer capacitor, the thickness of the dielectric ceramic layer is reduced to improve the capacitance of the capacitor and to reduce the size of the capacitor. In order to obtain a layer, barium titanate having a particle size of 0.2 to 1 μm, a narrow particle size distribution and good dispersibility is required.

Further, semiconductor capacitors, PTC thermistors having positive temperature characteristics, and the like are devices that use the electrical characteristics of the grain boundaries of ceramics. It is said that the particles have a uniform particle diameter. Therefore,
Also in these devices, in order to obtain good characteristics, it is necessary that barium titanate used as a raw material has a particle size of 1 to 5 μm and a narrow particle size distribution.

However, barium titanate produced by the conventional method cannot sufficiently meet the above demand.

That is, in the conventional method for producing barium titanate, barium titanate is produced by mixing and firing a titanium compound and a barium compound to cause a solid-phase reaction. In the case of the reaction, the barium titanate obtained has a large particle size due to the reaction at a high temperature, and the particle size does not decrease even after mechanical pulverization, and the particle size distribution is wide, so that the particle size can be controlled. However, since the shape was not uniform and the shape was not constant, the dispersibility was poor, and the above-mentioned demand could not be met at all.

In order to solve this problem, it has been proposed to produce barium titanate by a wet method. For example, JP-A-61-31345 proposes a method for producing barium titanate by a hydrothermal method or an alkoxide method.

However, these methods have the disadvantage that only fine barium titanate can be obtained, and that the particles have irregular shapes or particles are associated with each other. Therefore, even with these methods, it was not possible to obtain barium titanate with good dispersibility, which was controlled to the target particle diameter, in the particle diameter range of 0.2 μm to 5 μm.

Further, the barium titanate used for the core-shell sintered body must be of a tetragonal type. However, not only when the tetragonal barium titanate obtained by the solid phase method is calcined, but also by the wet method. Even in the case where the obtained pseudo-cubic barium titanate is calcined to obtain tetragonal barium titanate, particle growth occurs unevenly, and sintering between particles is severe, so that the particle size distribution is widened. Nevertheless, it was unable to meet the above demand.

[0011]

As described above, the conventional barium titanate cannot control the particle diameter sufficiently, has poor dispersibility, and has a disadvantage in the use of capacitors, PTs, and the like.
There has been a problem that it is not possible to sufficiently meet the demands for miniaturization and high performance of electronic components such as C thermistors.

Accordingly, an object of the present invention is to provide barium titanate which can be controlled to a particle diameter according to the purpose and has high dispersibility.

[0013]

Means for Solving the Problems The present inventors have conducted various studies to control the particle size and shape of barium titanate, and as a result, produced barium titanate by a wet reaction between a titanium compound and a barium compound. By using hydrogen peroxide, a spherical barium titanate whose particle diameter can be arbitrarily controlled can be obtained, thereby finding that the above object can be easily achieved, and completing the present invention. I have to do it.

That is, the barium titanate of the present invention comprises:
This is a spherical barium titanate having a narrow particle size distribution in which primary particles of fine barium titanate having a particle diameter of 0.005 to 0.1 μm are firmly coherently bonded in a spherical shape and having a narrow particle size of 0.2 to 5 μm. Barium titanate is obtained by performing a wet reaction between a titanium compound and a barium compound using hydrogen peroxide.

In the above-mentioned wet reaction between the titanium compound and the barium compound, hydrogen peroxide causes the formation reaction of barium titanate to proceed slowly, and the reaction proceeds to a particle size of 0.005 to 0.005.
It is considered that primary particles of barium titanate having a particle diameter of 0.2 to 5 μm in which 0.1 μm primary particles of barium titanate are aggregated in a true sphere form a spherical particle having a narrow particle size distribution.

[0016] The barium titanate in the form of spherical particles is formed by strongly aggregating the primary particles of barium titanate, and does not collapse in the handling operation during the production of electronic components such as capacitors and PTC thermistors. It is considered that the primary particles of barium titanate are not only physically aggregated but also form a kind of chemical bond.

The particle size of the obtained barium titanate can be arbitrarily controlled by changing the reaction conditions of the wet reaction.

The spherical barium titanate thus obtained can be used as a raw material for electronic components such as capacitors and PTC thermistors, that is, a raw material for electroceramics. Can be changed to cubic or tetragonal to obtain a more preferable electroceramic raw material in which the particle shape and grain boundary of the ceramic can be more easily controlled.

That is, when the above-mentioned spherical barium titanate is calcined at 600 ° C. or more, the crystal form changes from pseudo cubic to cubic or tetragonal, and the crystallinity is good. Although it becomes easier to control the particle size and grain boundary, these cubic or tetragonal barium titanate is literally spherical spherical barium titanate before calcining, and there are few contact points between particles Therefore, there is little sintering by calcining, and the particle diameter of the spherical barium titanate before calcining is almost maintained,
The particle size distribution is narrow and the dispersibility is excellent.

When the spherical barium titanate is reacted again under pressure (hydrothermal reaction), a denser spherical barium titanate can be obtained, and the particle diameter and grain boundary of the ceramic can be more easily controlled. It can be.

Further, in the present invention, when producing spherical barium titanate, barium titanate particles or other perovskite type compounds having a particle diameter smaller than the particle diameter of the spherical barium titanate to be produced are used as crystal nuclei. By adding the particles, spherical barium titanate containing particles having different particle diameters or particles having different compositions can be obtained.

The different particle size or different composition particles contained in the spherical barium titanate improve the electrical characteristics of the ceramic or promote the improvement of the crystallinity of the particles by firing or calcining. Therefore, it becomes a factor for further improving the characteristics of the spherical barium titanate.

Next, the [reaction raw material] and [reaction method] used for producing the spherical barium titanate of the present invention will be described in detail.

[Reaction Material] In the present invention, a titanium compound and a barium compound are used as reaction materials, and hydrogen peroxide is used during the reaction. Therefore, the order of the titanium compound, the barium compound, and the hydrogen peroxide is as follows.

The titanium compound can be used without particular limitation as long as it produces a barium compound and a perovskite-type barium titanate. The titanium compound may be partially dissolved in an aqueous solution of hydrogen peroxide or may be used. Alternatively, those that completely dissolve are preferred, and those that contain as little as possible components that deteriorate the properties of the resulting barium titanate when mixed into barium titanate are preferred.

Preferred examples of the titanium compound from the above viewpoint include inorganic titanium compounds such as titanium oxide and titanium hydroxide, and organic titanium compounds such as titanium oxalate and titanium alkoxide.

Industrially, readily available titanium oxide and titanium hydroxide are frequently used. When titanium hydroxide is used, the ignition loss is measured to determine the weight of titanium oxide (TiO ₂ ) in the titanium hydroxide, and the weight of the titanium oxide is used as a standard for a quantitative ratio in a wet reaction with a barium compound. It is practically preferable to use In addition, in measuring the ignition loss, it is suitable to use heating at 1000 ° C. for 2 hours as a reference.

As the barium compound, any compound can be used without any particular limitation as long as it reacts with the above-mentioned titanium compound to produce perovskite-type barium titanate. In general, a basic barium compound is used. Is done.

Further, it is preferable that the barium titanate contains as little as possible a component which deteriorates its properties by being mixed into the resulting barium titanate. From such a viewpoint, preferred barium compounds include, for example, barium hydroxide and barium oxide. And alkoxides of barium.

As the hydrogen peroxide, various ones can be used without any particular limitation. However, usually 30% (% by weight, hereinafter the same) of a commercially available hydrogen peroxide is used in view of availability and easy handling. Hydrogen water, 35% aqueous hydrogen peroxide, 50% aqueous hydrogen peroxide, 60% aqueous hydrogen peroxide and the like are used.

Regarding the [reaction method], there is no particular limitation on the order of adding these titanium compound, barium compound, and hydrogen peroxide. However, except when reacting at a dilute concentration, before adding the barium compound, It is preferable to mix and react with hydrogen peroxide. That is, unless hydrogen peroxide is added to a system in which a barium compound is present, except where the reaction is performed at a dilute concentration, sparingly soluble barium oxide (BaO ₂ ) is generated and precipitates, which makes it impossible to use in the reaction. is there.

The amount of hydrogen peroxide to be used is 0.1 to less than the molar ratio of hydrogen peroxide to the titanium compound (converted to titanium oxide), that is, H ₂ O ₂ / TiO ₂ (molar ratio).
10 is preferred.

When the amount of hydrogen peroxide exceeds 10 in molar ratio with respect to the titanium compound, the effect is not increased, and it is only economical to react with the titanium compound, which is uneconomical. On the other hand, if the amount of hydrogen peroxide is less than 0.1 in terms of the molar ratio with respect to the titanium compound, the effect of adding hydrogen peroxide cannot be sufficiently obtained.

When a titanium compound is mixed with hydrogen peroxide, it usually reacts to produce a peroxide of titanium and yellow. This reaction can be carried out completely and used as a completely dissolved aqueous solution of titanium peroxide, or it can be used as a suspension in which titanium peroxide has been produced.

For example, when the concentration of titanium oxide in the titanium hydroxide slurry is as thin as about 0.05 to 0.25 mol / l, if the hydrogen peroxide is mixed at least three times in molar ratio with respect to titanium, It becomes a completely dissolved aqueous solution of the substance.

However, when the concentration in terms of titanium oxide in the titanium hydroxide slurry is as high as 1 mol / l, or when crystalline titanium oxide is used regardless of the concentration, the amount of hydrogen peroxide can be reduced. Even if it is changed, it does not become a completely dissolved aqueous solution, but becomes a suspension solution. However, there is no problem in producing spherical barium titanate whether it is a completely dissolved aqueous solution of titanium peroxide or a suspended solution as described above.

The temperature at the time of mixing the hydrogen peroxide may be ordinary temperature. However, in order to obtain a homogeneous aqueous solution or suspension of the peroxide of titanium in a relatively short time, the temperature is preferably from 40 to 100 ° C.
It is preferable to heat the mixture.

The concentration of the titanium compound in terms of titanium oxide is 0.01 to 2.0 with the barium compound added.
5 mol / l, particularly preferably 0.06-1 mol / l. If the above concentration exceeds 2.5 mol / l, it becomes difficult to stir with high viscosity, and barium titanate obtained by reacting with the barium compound has a non-uniform particle size. When the above concentration is lower than 0.01 mol / l, the reaction rate is significantly reduced.

Prior to the reaction with the barium compound, 0.01 to 10% of a trace metal, nonmetal or a compound thereof is added as an additive for improving the characteristics in the case of electroceramic formation and as a sintering aid. May be added.

The molar ratio of barium to titanium, that is, Ba / Ti (molar ratio) is preferably 0.8 to 10, and more preferably 0.8 to 10 with respect to the aqueous solution or suspension of titanium peroxide thus obtained. A barium compound is added, uniformly mixed and reacted so as to be 1 to 3.

At this time, the titanium compound and the barium compound react with each other to produce pseudo-cubic perovskite-type barium titanate.
In order to obtain barium titanate spherical particles having a diameter of 0.1 μm and secondary particles having a particle diameter of 0.2 to 5 μm, the production reaction of barium titanate is not completed within 1 hour, preferably within 4 hours. Thus, the molar ratio of titanium to barium,
It is preferable to set the concentration of the barium compound, the reaction temperature, and the like.

In order to make the obtained spherical barium titanate uniform in particle diameter and narrow the particle size distribution, it is preferable to mix the titanium compound and the barium compound at a temperature lower than the temperature at which the reaction starts.

Further, the temperature at which the reaction between the titanium compound and the barium compound is completed in 4 hours, and 50 ° C from the temperature.
0.1C below the temperature, desirably between the temperature at which the reaction is completed in 4 hours and 40C below that temperature.
It is preferable to carry out the aging reaction for at least one hour, preferably at least one hour. After the aging reaction, the reaction is preferably completed at a temperature not lower than the temperature at which the reaction is completed in 4 hours. The completion of the above-mentioned reaction means a state in which the integrated intensity of barium titanate by X-ray diffraction does not substantially change even if the reaction is further continued.

Usually, the aging reaction is carried out at 40 to 100 ° C, preferably 60 to 100 ° C. This aging reaction is performed under normal pressure or reduced pressure. For example, when this aging reaction is performed under pressure using a closed vessel, the obtained barium titanate is liable to be fine particles of 0.1 μm or less, and even when it is 0.2 μm or more, non-spherical particles enter. And the particle size distribution is wide, and the particle size distribution of the present invention is not limited to 0.1.
Barium titanate having a spherical shape of 2 to 5 μm cannot be obtained. This tendency is particularly remarkable when a pressure reaction is performed at 100 ° C. or higher.

During the reaction, it is preferable to flow nitrogen into the reaction system so that the barium compound does not react with components such as carbon dioxide in the air.

As described above, the particle size is 0.005 to 0.005.
Particle size of 0.2 to 5 μm composed of 0.1 μm primary particles
m, a spherical particle of primary particles is obtained between the particle diameter of the primary particles and the particle diameter of spherical barium titanate which is a secondary particle in the present invention. It is required that the particle diameter be 1/3 or less of the particle diameter of barium titanate. This is because if the particle diameter of the primary particles is larger than 1/3 of the particle diameter of the spherical spherical barium titanate which is the secondary particle, the sphericity is impaired and the spherical spherical barium titanate with good dispersibility cannot be obtained. It is. In particular, the particle diameter of the primary particles is preferably 1/5 or less of the particle diameter of the truly spherical barium titanate.

In the present invention, the particle diameter of the spherical barium titanate is specified to be 0.2 to 5 μm.
This is for the following reason. That is, when the particle diameter is smaller than 0.2 μm, the dispersibility is poor. For example, the dispersibility in the binder during molding before ceramic formation is poor, and it is difficult to obtain a uniform molded body. Further, when the particle diameter is 5
If it is larger than μm, it will not be possible to adapt to the trend of thinning and miniaturizing electronic ceramic parts such as capacitors and PTC thermistors.

Further, in the present invention, it is required that the primary particles have a particle size of 0.005 to 0.1 μm, for the following reason. In other words, those having a primary particle diameter of less than 0.005 μm cannot be obtained by a wet method, and those having a primary particle diameter of more than 0.1 μm require a high temperature for firing and calcining, and have low dispersibility with less sintering. It becomes difficult to obtain good barium titanate.

Next, factors for controlling the particle diameter and particle shape of barium titanate will be described in detail with reference to actual examples. For example, a slurry having a titanium oxide concentration of 0.312 mol / l is obtained using a titanium hydroxide cake obtained by hydrolyzing an aqueous solution of titanium tetrachloride with aqueous ammonia. Hydrogen peroxide solution is added to this slurry with H ₂ O ₂ / T
iO ₂ (molar ratio) = 6.35 and mixed at 60 ° C
For 2 hours to obtain a suspension solution.

The temperature of the aqueous solution is lowered to 40 ° C., and barium hydroxide / octahydrate is added to the aqueous solution so that Ba / Ti (molar ratio) becomes 1.4 and mixed. After mixing
The aging reaction is carried out at 70 ° C. for 2 hours while stirring, and then the reaction is carried out at 100 ° C. for 4 hours to obtain spherical barium titanate having an average particle diameter of 1 μm.

First, the effect of the concentration of the solution on the particle size and shape of the barium titanate particles will be described with reference to the above reaction examples.

As the concentration of the solution, especially the barium ion concentration, increases, the particle size tends to decrease.

In this reaction example, assuming that Ba / Ti (molar ratio) = 1.4 is constant, if the concentration in terms of titanium oxide in the solution becomes higher than 0.312 mol / l, the barium ion concentration is accordingly increased. Since it increases, the particle diameter of barium titanate becomes smaller than 1 μm in the above reaction example. Conversely, when the concentration in terms of titanium oxide becomes lower than 0.312 mol / l, the barium ion concentration decreases accordingly, and the particle diameter becomes larger than 1 μm.

As for the reaction temperature between the titanium compound and hydrogen peroxide, the higher the temperature, the smaller the particle size of barium titanate, and the lower the temperature, the larger the particle size of barium titanate.

Specifically, a titanium compound slurry and hydrogen peroxide are mixed to prepare a completely dissolved aqueous solution or suspension of titanium peroxide. In this case, the titanium compound slurry and hydrogen peroxide are mixed. And then mix the solution with 20-1
Age at 00 ° C. As the aging temperature increases, the particle size decreases, and as the aging temperature decreases, the particle size increases.

With respect to Ba / Ti (molar ratio), as the ratio increases, the barium ion concentration increases.
The particle size of barium titanate tends to be small.

In the above reaction example, the amount of the barium compound is set to Ba / Ti (molar ratio) = 1.4, but if it is more than that, the barium ion concentration increases, the reaction speed increases, and the particle shape becomes smaller. No change, but particle size is small.
However, in the presence of an excessively large amount of barium ion, for example, when Ba / Ti (molar ratio) exceeds 10, barium titanate no longer forms an aggregate, and fine particles are generated.

When the amount of barium hydroxide is smaller than Ba / Ti (molar ratio) = 1.4, the barium ion concentration decreases and the particle shape does not change but the particle diameter increases.
However, the reaction itself no longer takes place in the presence of too little barium ions, for example with Ba / Ti (molar ratio) less than 0.8.

However, even if Ba / Ti (molar ratio) is temporarily less than 0.8, Ba / Ti
When the (molar ratio) is 0.8 or more, spherical barium titanate can be generated.

Next, the effect of the aging reaction temperature on the particle size will be described. The particle size becomes larger as the aging reaction is performed for a longer time near the temperature at which the titanium compound and the barium compound start reacting to produce barium titanate. . In addition, the particle size decreases as the aging reaction temperature increases.

For example, an aging reaction at a temperature lower than 70 ° C., for example, an aging reaction at 50 ° C. for 2 hours, and a aging reaction at a temperature at which the reaction rate becomes extremely slow, and thereafter,
When the temperature is raised to 100 ° C., the obtained barium titanate is heated from 20 ° C. to 100 ° C. as quickly as possible to obtain 1 barium titanate.
As in the case of barium titanate obtained by an aging reaction at 00 ° C., it becomes a true sphere with an average particle diameter of 0.6 μm. That is,
An aging reaction at such a low temperature that the reaction does not proceed is meaningless because the same result is obtained with or without the reaction.

When the ripening reaction is carried out at a temperature higher than 70 ° C., the reaction rate increases and the particle shape does not change but the particle diameter decreases. For example, use an airtight container and set the aging reaction temperature to 1
If the temperature is raised to about 80 ° C., the reaction rate becomes too fast,
It is no longer possible to maintain a particle shape that forms an aggregate, and the resulting barium titanate is all fine particles.

Further, the ripening reaction temperature and the ripening reaction time were made longer than those in the above-mentioned reaction examples,
To 10 ° C. over 10 hours to effect an aging reaction.
When the reaction is completed at 0 ° C. for 4 hours to complete the reaction, the particle size of the obtained barium titanate becomes larger than in the case of the above reaction example, and the average particle size becomes 2.5 μm.

With the above-mentioned reaction raw materials and reaction method, barium barium titanate having a narrow particle size distribution and a narrow particle size distribution composed of primary particles having a particle size of 0.005 to 0.1 μm and having a particle size of 0.2 to 5 μm can be obtained. .

The obtained spherical barium titanate is usually adjusted to a Ba / Ti (molar ratio) of 0.95 to 1.05, preferably 0.99 to 1.02, by washing with water, acid treatment or the like. Used.

Since the above-mentioned spherical barium titanate has a perfect spherical shape, it is excellent in dispersibility. In addition, by selecting an aging reaction temperature, a concentration of a titanium compound, Ba / Ti (molar ratio), etc. Since the particle size can be arbitrarily controlled, it is possible to control the particle size according to the purpose with miniaturization and high performance of electronic components such as capacitors and PTC thermistors, and with high dispersibility. It can fully respond to the demand that there is.

Next, the particle size is 0.005 to 0.1 μm.
m of a spherical spherical barium titanate composed of primary particles of 0.2 to 5 μm [cubic barium titanate and tetragonal barium titanate obtained by calcining], and having a particle diameter of 0.1 to 5 μm.
0.2 to 5 composed of primary particles of 005 to 0.1 μm
μm spherical barium titanate [compact spherical barium titanate obtained by reacting again under pressure] and the present invention [spheroidal titanate containing heterogeneous particles or heterogeneous particles therein] Barium] will be described.

[ Cubic Barium Titanate Obtained by Calcination
Barium titanate) can be used as it is as a raw material for electroceramics.
The primary particles are in an aggregated state, and the crystal form is pseudo cubic.

When this is calcined at 600 ° C. or higher, the crystal form changes to cubic or tetragonal, and barium titanate having good crystallinity and more easily controlling the particle size and grain boundaries of ceramics is obtained. .

For example, this spherical barium titanate is converted to 6
When calcined at 00 to 1100 ° C., cubic or tetragonal spherical barium titanate with good sintering and good dispersibility, which maintains the particle diameter and shape of the spherical barium titanate, is obtained.

When calcined at 900 to 1300 ° C.,
A tetragonal barium titanate is obtained. In this case, when the temperature is low and the particle diameter is large, the particles become spherical. Then, when the particle diameter is small or when calcined at a high temperature, a cuboid single crystal powder is obtained.

By the above-mentioned calcination, barium titanate becomes a high-density one with good crystallinity. When formed into ceramics, it becomes an electroceramic raw material whose particle diameter and grain boundaries are more easily controlled.

Since the cubic barium titanate and the tetragonal barium titanate are literally spherical in shape before the calcination and have few contact points between the particles, the cubic barium titanate and the tetragonal barium titanate have a small number of contacts between particles. There is little sintering, so the particle size before calcination is almost maintained,
The particle size distribution is narrow and the dispersibility is excellent.

As described above, the cubic barium titanate and the tetragonal barium titanate can control the particle diameter according to the purpose which is the characteristic of the spherical barium titanate before calcination, and can achieve high dispersion. It is highly useful as compared with one obtained by calcining barium titanate obtained by a conventional wet method.

[ Dense reaction obtained by reacting again under pressure
Spherical barium titanate] The particle size of the present invention is 0.005 to 0.005.
Reaction of 0.2-5 μm spherical barium titanate composed of 0.1 μm primary particles under pressure again (hydrothermal reaction)
By doing so, a more dense spherical barium titanate can be obtained.

The hydrothermal reaction under such pressure can be carried out on isolated spherical barium titanate, or without isolation, following the production of spherical barium titanate under normal pressure. You can also do it.

When a barium compound is added at the time of the hydrothermal reaction under the above pressure, there is an effect of promoting the growth of primary particles. The spherical spherical barium titanate on which such primary particles are grown is a suitable raw material when obtaining a ceramic in which an additive is arranged at a grain boundary.

The barium titanate obtained by the hydrothermal reaction under pressure as described above can be used as it is, or can be calcined and used as a calcined powder.

The spherical barium titanate obtained by the hydrothermal reaction under pressure as described above is denser, and it is easier to control the particle size and the grain boundary of the ceramic. As a result, the density of the ceramic is improved. In addition, it is possible to more easily achieve the improvement of the withstand voltage and the improvement of the mechanical strength.

[ Particles of Different Particle Size or Different Composition Inside
Containing spherical barium titanate] Further, by applying the method of the present invention, it is possible to produce a spherical barium titanate containing particles having different particle diameters or particles having different compositions.

For example, a tetragonal barium titanate having a particle diameter of 0.1 μm or more and having good crystallinity smaller than the particle diameter of the target product particles is used, and the tetragonal barium titanate is used as a crystal nucleus. By applying the method described above, a spherical barium titanate containing tetragonal barium titanate particles having different particle diameters therein can be produced. By calcining the true spherical barium titanate containing tetragonal barium titanate particles therein, tetragonal rectangular parallelepiped barium titanate can be more easily obtained.

Further, the high temperature sinterability of strontium titanate, barium zirconate, barium zirconate titanate, etc., having a particle size smaller than the target product particle size can be used to improve the electrical characteristics of capacitors, PTC thermistors, etc. By using the method of the present invention with the contributing perovskite compound as a crystal nucleus, it is possible to produce spherical barium titanate containing heterogeneous particles such as strontium titanate, barium zirconate, and barium zirconate titanate therein. it can.

By firing the spherical barium titanate containing heterogeneous particles therein, low-temperature sintering can be performed while reacting the heteronuclear particles serving as crystal nuclei with barium titanate. This makes it possible to improve the electrical properties of barium titanate based on high-temperature sinterable hetero-composition particles by low-temperature sintering.

The spherical barium titanate containing these different particle diameter particles or different composition particles inside can be obtained by a wet method by using a well-crystallized different particle diameter particle or a different composition particle obtained by a solid phase method, or a wet method. The obtained particles are calcined to obtain good-crystallinity particles having different particle diameters or different composition, into titanium alkoxide, an aqueous solution of titanium salt, or titanium hydroxide, titanium oxide obtained by hydrolyzing these, or the like. It is obtained by adding and mixing, and then mixing and reacting hydrogen peroxide and a barium compound.

The spherical barium titanate containing particles of different particle diameters or particles of different composition obtained by applying the method of the present invention has a narrow particle size distribution and high dispersibility. It has the characteristics of spherical barium titanate.

In producing the above-mentioned spherical barium titanate containing particles having different particle diameters or different composition, hydrogen peroxide may be directly added to an aqueous solution of a titanium alkoxide or a titanium salt. It may be added after their hydrolysis. That is, the addition and mixing may be performed at any stage before the barium compound is mixed and reacted.

Mixing of particles of different particle size or particles of different composition
It is preferably carried out before the hydrolysis of the aqueous solution of titanium alkoxide or titanium salt. This is added before the hydrolysis, and the titanium hydroxide is adhered to the surface of the particles by the hydrolysis, and the particles having different particle diameters or the different composition are surely titanic acid by the reaction with the barium compound. This is because it can be taken into barium. Further, it is preferable that the different particle diameter particles and the different composition particles are sufficiently dispersed in a wet system before mixing.

The tetragonal barium titanate used in the production of the spherical barium titanate containing tetragonal barium titanate therein is not necessarily limited, but the spherical barium titanate of the present invention is not limited. It is preferable to use a tetragonal rectangular parallelepiped barium titanate obtained by calcining, a narrow particle size distribution obtained by a firing method, an autoclave method, or the like.

[0089]

According to the present invention, the spherical barium titanate of the present invention can control the particle diameter according to the purpose, and is spherical and excellent in dispersibility.

Therefore, the spherical barium titanate of the present invention has been required for barium titanate as electronic components such as capacitors, PTC thermistors, and piezoelectrics have been reduced in size and improved in performance. The particle size can be controlled according to the particle size and the dispersibility is high. "

The spherical barium titanate of the present invention can be used as it is as a raw material for electronic components such as the above-mentioned capacitors and PTC thermistors. However, when the spherical barium titanate of the present invention is calcined, sintering occurs. A small particle size distribution and high dispersibility of cubic spherical barium titanate or tetragonal spherical barium titanate can be obtained while maintaining the particle diameter and shape of the spherical barium titanate before calcining.

These spherical barium titanates are different from barium titanates obtained by a conventional solid phase method or a wet method.
Since the particle size distribution is narrow and spherical, the amount of air entrained during molding is small, and therefore, the occurrence of lamination is suppressed, and it is possible to obtain a uniform and high-density molded body. The ultimate density is also greatly improved.

Therefore, by using the above-mentioned spherical barium titanate, it is possible to obtain a capacitor having a uniform particle diameter and excellent dielectric properties. Furthermore, by calcining the true spherical barium titanate at a high temperature, it is possible to obtain a tetragonal rectangular parallelepiped barium titanate having less sintering and a narrow particle size distribution.

This tetragonal rectangular parallelepiped barium titanate is
Because it is a high-density barium titanate that is tighter than the above-mentioned spherical barium titanate, it is easier to strictly control the particle size and grain boundaries of the ceramic, so this tetragonal rectangular parallelepiped barium titanate is By using such a capacitor, it is possible to obtain a capacitor, a PTC thermistor, and the like having better dielectric properties.

Further, by calcining spherical barium titanate containing tetragonal barium titanate having a different particle diameter therein, it is possible to obtain a tetragonal rectangular parallelepiped barium titanate having a uniform particle diameter more easily. Thus, a capacitor, a PTC thermistor, and the like having excellent dielectric characteristics as described above can be more easily obtained.

Further, by firing a spherical barium titanate containing therein a high-temperature sinterable heterocomposite particle such as strontium titanate, barium zirconate, barium zirconate titanate, etc., the composition becomes different from that of barium titanate. Low-temperature sintering can be performed while reacting with the particles, and the electrical characteristics of a capacitor, a PTC thermistor, and the like can be more easily improved.

[0097]

Next, the present invention will be described more specifically with reference to examples.

Example 1 Titanium tetrachloride aqueous solution (Titanium 1 manufactured by Osaka Titanium Co., Ltd.)
(Containing 4%) was hydrolyzed with 5% aqueous ammonia, and the obtained titanium hydroxide gel was filtered and washed with water, and a titanium hydroxide cake [I with a titanium oxide concentration of 12.3% as reduced by ignition loss was obtained. ] Was obtained.

To an aqueous solution obtained by uniformly dispersing 200 g of this titanium hydroxide cake [I] in 654 g of water, 221 g of 30% hydrogen peroxide was added. At this time, the molar ratio of hydrogen peroxide to titanium oxide (hereinafter, referred to as “H ₂ O ₂ / TiO ₂ (molar ratio)”) was 6.34. The titanium oxide concentration in the obtained slurry was 30% hydrogen peroxide aqueous solution of 7%.
It was 0.312 mol / l when 0% was calculated as water.

The obtained slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution [II]. The suspension was cooled to 40 ° C. by natural cooling, and 136 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.
4] and add 0.5 to 100 ° C. while flowing nitrogen.
The reaction was heated for 4 hours and refluxed for 4 hours.

The barium titanate produced by this reaction is a true spherical aggregate composed of primary particles having a particle diameter of 0.01 to 0.03 μm, and has a 90% number distribution particle diameter determined by observation with an electron microscope. 0.63-0.77 μm,
The particle size distribution was narrow and the average particle size was 0.70 μm.

FIG. 1 is an electron micrograph (magnification: 30,000) showing the particle structure of barium titanate produced according to Example 1. As shown in FIG. 1, the barium titanate produced according to Example 1 has a high sphericity in particle shape even when it is expanded 30,000 times, and has a substantially uniform particle diameter, and a particle size distribution. You can see that is narrow.

Example 2 200 g of the titanium hydroxide cake [I] produced in Example 1
Was dispersed in 217 g of water, and 820 g of a 30% hydrogen peroxide solution [H ₂ O ₂ / TiO ₂ (molar ratio) = 1
0.0], and a slurry having a titanium oxide concentration of 0.312 mol / l was obtained in the same manner as in Example 1.

The obtained slurry was uniformly mixed at 20 ° C. for 2 hours to obtain a suspension solution. 136 g of barium hydroxide / octahydrate was added to this suspension solution [Ba / Ti (molar ratio) = 1.4].
Was added, the temperature was raised from 20 ° C. to 100 ° C. for 0.75 hours, and the mixture was reacted for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.69 to 1.03 μm observed by an electron microscope, and a narrow particle size distribution.
The average particle size was 0.86 μm.

Example 3 200 g of the titanium hydroxide cake [I] produced in Example 1
82 g of 30% aqueous hydrogen peroxide [H ₂ O ₂ / TiO ₂ (molar ratio) = 2.
35], and the titanium oxide concentration was set to 0.3 as in Example 1.
A slurry of 312 mol / l was obtained.

The obtained slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution. After cooling this suspension solution to 40 ° C., 136 g of barium hydroxide / octahydrate was added therein.
[Ba / Ti (molar ratio) = 1.4] was added, the temperature was raised to 100 ° C. in 0.5 hour while flowing nitrogen, and the reaction was carried out for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 0.01 to 0.03 μm, and has a 90% number distribution particle size of 0.58 to 0.70 μm observed by an electron microscope, and a narrow particle size distribution.
The average particle size was 0.64 μm.

Example 4 200 g of the titanium hydroxide cake [I] produced in Example 1
Was uniformly dispersed in 80 g of water, and 221 g of 30% aqueous hydrogen peroxide [H ₂ O ₂ / TiO ₂ (molar ratio) = 6.
35] to obtain a slurry having a titanium oxide concentration of 0.75 mol / l.

The obtained slurry was uniformly mixed at 20 ° C. for 2 hours to obtain a suspension [III]. 116 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio)]
= 1.2] and 0.75 from 20 ° C to 100 ° C.
The reaction was heated for 4 hours and refluxed for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 0.01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.27 to 0.43 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.35 μm.

FIG. 2 is an electron micrograph (magnification: 30,000) showing the particle structure of the spherical barium titanate produced in Example 4, and FIG. 3 is a spherical titanate produced in Example 4. It is an electron micrograph of 100,000 times magnification which shows the particle structure of barium.

It can be seen that the true spherical barium titanate of Example 4 has a high spherical shape and a substantially uniform particle size even when enlarged to 100,000 times, and has a narrow particle size distribution.

Example 5 To a suspension solution [III] similar to that prepared in Example 4, 194 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 2.0] was added. The same operation as in Example 4 was performed to obtain barium titanate.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.15 to 0.25 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.20 μm.

Example 6 100 g of the titanium hydroxide cake [I] produced in Example 1
Was dispersed in 2295 g of water, and 111 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO ₂ (molar ratio) =
6.35] and the titanium oxide concentration is 0.06 mol /
1 slurry was obtained.

The obtained slurry was uniformly mixed at 20 ° C. for 2 hours to obtain an aqueous solution in which titanium peroxide was completely dissolved. 194 g of barium hydroxide / octahydrate [Ba / T
i (molar ratio) = 4.0], and the temperature was changed from 20 ° C to 100 ° C.
The reaction was heated for 0.75 hours and refluxed for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.45 to 0.83 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.64 μm.

Example 7 A suspension solution [II] similar to that prepared in Example 1 was added to 2
At 0 ° C., 136 g of barium hydroxide / octahydrate [Ba / Ti
(Molar ratio) = 1.4], the temperature was raised to 60 ° C. in 0.25 hours, and aged at 60 ° C. for 3 hours.
The temperature was raised in 0.5 hours until the reaction was carried out at 100 ° C. while refluxing for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.70 μm.

Example 8 The same suspension solution [II] as that prepared in Example 1 was added to 2
At 0 ° C., 136 g of barium hydroxide / octahydrate [Ba / Ti
(Molar ratio) = 1.4], and the mixture was heated to 80 ° C. in 0.5 hours, aged at 80 ° C. for 3 hours, and then heated to 100 ° C. in 0.25 hours. The reaction was carried out for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 1.22 to 1.82 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 1.52 μm.

Example 9 The same suspension solution [II] as that prepared in Example 1 was added to
At 0 ° C., 96 g of barium hydroxide octahydrate [Ba / Ti (molar ratio) = 0.99] was added, the temperature was raised to 80 ° C. in 0.5 hours, and after aging at 80 ° C. for 3 hours, Further, 42 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 0.
41] was added, the temperature was raised from 80 ° C. to 100 ° C. in 0.25 hours, and the mixture was reacted at 100 ° C. for 6 hours while refluxing.
The total amount of barium hydroxide and octahydrate added was 138 g,
This is the molar ratio of barium to titanium, ie [Ba
/ Ti (molar ratio)].

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 03 to 0.1 μm, and has a 90% number distribution particle diameter of 0.34 to 0.62 μm observed by an electron microscope, a narrow particle size distribution, and an average particle diameter of It was 0.48 μm.

Example 10 A suspension solution [II] similar to that prepared in Example 1 was cooled to 40 ° C. by natural cooling, and then 87 g of barium hydroxide / octahydrate [Ba / Ti (mol Ratio) = 0.9]
Was added, and the temperature was raised to 80 ° C. in 0.5 hour under a nitrogen flow. After aging for 2 hours, 49 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 0.5] was further added. The mixture was added, immediately heated to 100 ° C., and reacted while refluxing for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 03 to 0.1 μm, and has a 90% number distribution particle diameter of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution, and an average particle diameter of It was 0.70 μm.

Comparative Example 1 200 g of the titanium hydroxide cake [I] prepared in Example 1
Was uniformly dispersed in 809 g of water, and the titanium oxide concentration was reduced to 0.3.
The solution was adjusted to 12 mol / l, and 136 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.4] was added to this aqueous solution for 20 times.
At 60 ° C. for 0.25 hours with a nitrogen flow, and after aging at 60 ° C. for 3 hours, 100 ° C.
Up to 0.25 hours and reflux at 100 ° C.
Allowed to react for hours.

The barium titanate thus obtained is a true spherical agglomerate composed of primary particles having a particle size of 0.01 to 0.03 μm. Was 0.14 to 0.42 μm and the average particle diameter was 0.28 μm, but the particle diameter was not constant, the shape was distorted, and it was far from a true sphere.

FIG. 4 is an electron micrograph (magnification: 30,000) showing the particle structure of barium titanate produced in Comparative Example 1. As shown in FIG. 4, the barium titanate produced according to Comparative Example 1 had an irregular particle diameter, an irregular shape, and was far from a true sphere.

Comparative Example 2 200 g of the titanium hydroxide cake [I] prepared in Example 1
Was uniformly dispersed in 809 g of water, and the concentration of titanium oxide was reduced to 0.1.
It was 312 mol / l.

136 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.4] was added to this aqueous solution at 20 ° C., and the temperature was raised to 100 ° C. in 0.5 hour while flowing nitrogen. The reaction was carried out for 4 hours while refluxing at 100 ° C.

The obtained barium titanate had a particle size of 0.1.
It is an agglomerate composed of primary particles of 0.01 to 0.03 μm, and has a 90% number distribution particle size of 0.08 to 0.16 μm as observed by electron microscopy, and an average particle size of 0.12
Although it was μm, the shape was distorted and it was far from a true sphere.

Example 11 A suspension solution [II] similar to that prepared in Example 1 was added to 2
At 0 ° C., 136 g of barium hydroxide / octahydrate [Ba / Ti
(Molar ratio) = 1.4] and 0.75 to 100 ° C.
The temperature was raised at a constant speed over time, and after aging at 100 ° C. for 4 hours under normal pressure, the mixture was placed in a closed container, heated to 180 ° C. under pressure for 1 hour, and reacted for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical aggregate composed of primary particles of 0.5 to 0.1 μm, and has a 90% number distribution particle size of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution, and an average particle size of It was 0.70 μm. This aggregate was very dense.

Example 12 The same suspension solution [II] as that prepared in Example 1 was added to 2
At 0 ° C., 136 g of barium hydroxide / octahydrate [Ba / Ti
(Molar ratio) = 1.4] and 0.75 to 100 ° C.
The temperature was raised over a period of time, followed by a reaction at 100 ° C. for 4 hours.

The obtained barium titanate was filtered and washed with water, and then slurried again with 1000 g of water, and 200 g of barium hydroxide / octahydrate was added to the slurry and mixed. The temperature was raised to 180 ° C. in 1 hour, and then the reaction was performed at 180 ° C. for 4 hours.

The obtained barium titanate has a particle size of 0.1.
It is a true spherical aggregate composed of primary particles of 0.5 to 0.1 μm, and has a 90% number distribution particle size of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution, and an average particle size of It was 0.70 μm.

Example 13 500 g of an aqueous solution of titanium tetrachloride (containing 16.4% of titanium)
After adding 410 g of urea and 4000 g of water and mixing,
The mixture was heated and refluxed for 4 hours while refluxing to obtain a slurry of finely particulate titanium oxide-containing titanium oxide having an anatase structure.

The obtained slurry was filtered and washed with water to obtain an anatase-type hydrous titanium oxide cake having a titanium oxide concentration of 21.0% in terms of weight by ignition loss.

The anatase-type hydrous titanium oxide cake 2
00g in an aqueous solution uniformly dispersed with 1228 g of water,
420 g [H ₂ O ₂ / TiO ₂ (molar ratio) = 7.06] was added. The concentration of titanium oxide in the obtained slurry was 0.312 mol / l when 70% of a 30% hydrogen peroxide solution was calculated as water.

The resulting slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution. 231.9 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.
4] and reacted at 100 ° C. for 6 hours under reflux.

The barium titanate obtained had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.70 μm.

Example 14 500 g of an aqueous solution of titanium tetrachloride (containing 16.4% of titanium)
3904 g of water and 137 g of 30% hydrogen peroxide solution [H ₂ O
₂ / TiO ₂ (molar ratio) = 2.35], uniformly mixed for 2 hours, hydrolyzed with aqueous ammonia, filtered and washed with titanium hydroxide, and converted by ignition loss. A titanium hydroxide cake (yellow) having a titanium oxide concentration of 13.0% by weight was obtained.

200 g of this titanium hydroxide cake was added to water 83
To the aqueous solution uniformly dispersed with 6 g, 43 g of 30% aqueous hydrogen peroxide [H ₂ O ₂ / TiO ₂ (molar ratio) = 1.18] was added. The titanium oxide concentration in the obtained slurry was 0.3
It was 12 mol / l.

The obtained slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution. 143.5 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.
4] was added and reacted at 100 ° C.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.63 to 0.77 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.70 μm.

Example 15 Distilled water (1000) was added to 102.4 g of titanium isopropoxide.
g of H ₂ O ₂ / TiO ₂ (molar ratio) in which 172 g of a 30% aqueous hydrogen peroxide solution is added.
= 7.06] and the titanium oxide concentration was 0.312 mol
1 / l. This aqueous solution was heated to 60 ° C. and mixed for 2 hours to obtain a suspension solution.

To the obtained suspension solution, 159 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.4] was added at 20 ° C.
, And the temperature was raised from 20 ° C to 100 ° C in 0.75 hours, and refluxed for 4 hours.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.44 to 0.60 μm observed by an electron microscope, and a narrow particle size distribution.
The average particle size was 0.52 μm.

Example 16 The spherical barium titanate having an average particle diameter of 0.70 μm obtained in Example 1 was filtered, washed with 3000 g of water, slurried with 1500 g of water, and heated to 60 ° C. for 1 hour. , The pH was adjusted to 8.50 by adding 10 ml of acetic acid, and the mixture was stirred at 60 ° C. for 1 hour, filtered, and 3,000 g
And then dried.

As a result of this treatment, the molar ratio of barium to barium titanate was 1.005. The molar ratio is a value determined by X-ray fluorescence measurement, and hereinafter, the molar ratio of barium to titanium in the calcined powder is a value determined by X-ray fluorescence measurement.

The obtained barium titanate powder was pulverized for 1 hour with a milling machine and calcined at 1000 ° C.

The barium titanate obtained by the above calcination is dense and free of sintering, and has a 90% number distribution particle diameter of 0.49 to 0.91 μm observed by an electron microscope.
m, the average particle diameter was 0.70 μm.

Example 17 100 g of the spherical barium titanate obtained in Example 1 was filtered, dried, slurried again with 1000 g of water, heated to 60 ° C., and added with 5 ml of acetic acid. p
H was adjusted to 8.80, and the mixture was subjected to an aging reaction at 60 ° C. for 1 hour, then, filtered, washed with 1000 g of water, and dried. As a result of this treatment, the molar ratio of barium to barium titanate was 1.018.

The obtained powder was cooled from 20 ° C. to 1100 ° C.
After heating at a constant speed for 1 hour and calcining at 1100 ° C for 2 hours,
The temperature was lowered to 0 ° C. at a constant speed for 3 hours.

The barium titanate obtained by the above-mentioned calcination was 90% by sintering without electron microscope observation.
It was a tetragonal rectangular parallelepiped barium titanate having a% number distribution particle diameter of 0.49 to 0.91 μm and an average particle diameter of 0.70 μm.

FIG. 5 is a magnification of 1 showing the particle structure of the tetragonal rectangular parallelepiped barium titanate produced in Example 17.
FIG. 6 is an electron microscope photograph of a tetragonal rectangular parallelepiped barium titanate manufactured according to Example 17 at a magnification of 20,000. As shown in FIGS. 5 and 6, the tetragonal rectangular parallelepiped barium titanate produced in Example 17 had a rectangular parallelepiped shape and a substantially uniform particle size.

Example 18 After adding yttrium nitrate having an yttrium content of 1% to the weight of titanium contained in an aqueous solution of titanium tetrachloride, hydrolysis was carried out with aqueous ammonia, and the obtained yttrium-containing titanium hydroxide gel was filtered. Washing with water to obtain an yttrium-containing titanium hydroxide cake having a titanium oxide concentration of 12.3% in terms of weight by ignition loss.

An aqueous solution obtained by uniformly dispersing 200 g of the obtained yttrium-containing titanium hydroxide cake with 654 g of water was
221 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO _2
2 (molar ratio) = 6.35], and the reaction was carried out in the same manner as in Example 1.

The obtained barium titanate had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 0.01 to 0.03 μm, and has a 90% number distribution particle size of 0.63 to 0.94 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.78 μm.

Example 19 200 g of the titanium hydroxide cake [I] prepared in Example 1
221 g of a 30% hydrogen peroxide solution in an aqueous solution obtained by uniformly dispersing water in 600 g of water and 54 g of isopropyl alcohol.
[H ₂ O ₂ / TiO ₂ (molar ratio) = 6.35]
Thereafter, the reaction was carried out in the same manner as in Example 1.

The barium titanate obtained had a particle size of 0.1.
It is a true spherical agglomerate composed of primary particles of 0.01 to 0.03 μm, and has a 90% number distribution particle diameter of 0.50 to 0.74 μm observed by an electron microscope, a narrow particle size distribution,
The average particle size was 0.62 μm.

Example 20 A 90% number distribution particle diameter of 0.8 produced by using hydrogen peroxide according to the present invention and observed by an electron microscope was 0.8.
After filtering and drying a true spherical barium titanate having an average particle diameter of 0.95 μm and a diameter of 5 to 1.05 μm, the temperature is reduced to 20 to 100 ° C.
The temperature was raised to 0 ° C. in 3 hours at a constant speed, calcined at 800 ° C. for 2 hours, and then lowered to 20 ° C. in 3 hours.

The barium titanate obtained by the above calcination is a cubic spherical barium titanate having no sintering and maintaining the particle diameter before calcination and having an average particle diameter of 0.95 μm. Barium acid had a narrow particle size distribution and was excellent in dispersibility.

FIG. 7 is an electron micrograph (magnification: 30,000) showing the particle structure of the cubic spherical barium titanate produced in Example 20. As shown in FIG. 7, the cubic spherical barium titanate of Example 20 had a high spherical shape and a substantially uniform particle diameter even when enlarged by 30,000 times.

Example 21 200 g of an aqueous solution of titanium tetrachloride (containing 16.4% of titanium)
600 g of water and 233 g of 30% hydrogen peroxide solution [H ₂ O ₂
/ TiO ₂ (molar ratio) = 3.00] was added and mixed, and then tetragonal barium titanate 8 having an average particle size of 0.2 μm was added.
0 g was added and mixed with stirring for 3 hours.

Next, 144 g of urea were added,
After heating at a constant speed to 0.5 to 100 ° C for 0.5 hour,
Under reflux for 4 hours to carry out a thermal hydrolysis reaction.

After the reaction, the slurry was repeatedly filtered and washed with water. 1200 g of water was added to the obtained barium titanate-containing titanium hydroxide cake and stirred, and 302 g of barium hydroxide / octahydrate [Ba / Ti (Molar ratio) = 1.
4], and the mixture was subjected to an aging reaction at 50 ° C. for 2 hours under a nitrogen flow, followed by a reaction at 100 ° C. for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.03 to 0.03 except for tetragonal barium titanate contained therein.
It is a true spherical agglomerate composed of 0.1 μm primary particles. This agglomerate is excellent in crystallinity, has a 90% number distribution particle size of 0.20 to 0.36 μm observed by an electron microscope, and has a particle size distribution. It was narrow and had an average particle size of 0.28 μm.

FIG. 8 is an electron micrograph (magnification: 50,000) showing the particle structure of the truly spherical barium titanate produced in Example 21. As shown in FIG. 8, the spherical barium titanate produced in Example 21 has a high spherical shape even when magnified 50,000 times.
It can be seen that the particle diameter is almost uniform and the particle size distribution is narrow.

Example 22 200 g of an aqueous solution of titanium tetrachloride (containing 16.4% of titanium)
Was added and mixed uniformly for 1 hour. Then, 80 g of tetragonal barium titanate having an average particle diameter of 0.8 μm was added, and the mixture was stirred for 3 hours and mixed.

Next, 5% ammonia water was added to the solution at pH 7
, And then repeated filtration and washing with water. 1000 g of water was added to the obtained barium titanate-containing titanium hydroxide cake and stirred, and then 200 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO ₂ (molar ratio) =
2.58] and stirred at 60 ° C. for 2 hours.

After the obtained slurry was cooled to 20 ° C., 302 g of barium hydroxide / octahydrate [Ba /
Ti (molar ratio) = 1.4], and the mixture was subjected to an aging reaction at 60 ° C. for 2 hours in a nitrogen flow, followed by a reaction at 100 ° C. for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.03 to 0.03 except for tetragonal barium titanate contained therein.
It is a true spherical agglomerate composed of 0.1 μm primary particles. This agglomerate is excellent in crystallinity, has a 90% number distribution particle size of 0.78 to 1.06 μm observed by an electron microscope, and has a particle size distribution. It was narrow and had an average particle size of 0.92 μm.

Comparative Example 3 The same suspension solution [II] as that prepared in Example 1 was added to 2
At 0 ° C., 136 g of barium hydroxide / octahydrate [Ba / Ti
(Molar ratio) = 1.4] in a closed container at 180 ° C.
The temperature was raised at a constant rate in 0.75 hours until
Allowed to react for hours. The obtained barium titanate was fine particles having a particle size of 0.02 to 0.1 μm.

Example 23 600 g of water was added to 200 g of an aqueous titanium tetrachloride solution (containing 16.4% of titanium) and mixed uniformly for 1 hour.
80 g of barium zirconate having an average particle diameter of 0.8 μm manufactured by a solid phase method was added, and the mixture was stirred for 3 hours and mixed.

Next, 5% ammonium water was gradually added until the pH of the solution reached 7, and then filtration and washing were repeated, and 1000 g of water was added to the obtained barium zirconate-containing titanium oxide cake, followed by stirring. After that, 200 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO ₂ (molar ratio) =
2.58] and stirred at 60 ° C. for 2 hours.

After the obtained slurry was cooled to 20 ° C., 302 g of barium hydroxide / octahydrate [Ba /
Ti (molar ratio) = 1.4], and the mixture was subjected to an aging reaction at 60 ° C. for 2 hours in a nitrogen flow, followed by a reaction at 100 ° C. for 4 hours under reflux.

The obtained barium zirconate-containing barium titanate is a true spherical aggregate composed of primary particles having a particle size of 0.03 to 0.1 μm except for the barium zirconate contained therein. The aggregate has excellent crystallinity and has a 90% number distribution particle size of 0.78 to
1.06 μm, narrow particle size distribution, average particle size 0.9
It was 2 μm.

Comparative Example 4 A commercially available barium titanate produced by a wet method was observed with an electron microscope.
μm, with a lot of sintering, and non-uniform particles having only depressed particles.

FIG. 9 is an electron micrograph (magnification: 100,000-fold) showing the particle structure of the barium titanate of Comparative Example 4. As shown in FIG. 9, it can be seen that the barium titanate of Comparative Example 4 has a lot of sintering and a non-uniform particle shape.

Comparative Example 5 A commercially available barium titanate produced by the solid phase method was observed with an electron microscope.
μm, a lot of sintering, and tetragonal barium titanate, but the particles were indeterminate in shape and had a wide particle size distribution.

FIG. 10 is an electron micrograph (magnification: 10,000) showing the particle structure of barium titanate of Comparative Example 5. 10 is clearly compared with FIG. 5 (FIG. 5 is an electron micrograph of 10,000 times magnification showing the particle structure of the tetragonal rectangular parallelepiped barium titanate manufactured according to Example 17 of the present invention). Thus, the tetragonal rectangular parallelepiped barium titanate produced according to Example 17 of the present invention has less shape, particle size distribution and sintering than the commercially available tetragonal barium titanate produced by the solid phase method. It shows excellent characteristics in any point such as lack.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (magnification: 30,000) showing the particle structure of a truly spherical barium titanate produced according to Example 1.

FIG. 2 is an electron micrograph (magnification: 30,000) showing the particle structure of a truly spherical barium titanate produced according to Example 4.

FIG. 3 is an electron micrograph (magnification: 100,000 times) showing the particle structure of a truly spherical barium titanate produced according to Example 4.

FIG. 4 is an electron micrograph (magnification: 30,000) showing the particle structure of barium titanate produced according to Comparative Example 1.

FIG. 5 is an electron micrograph (magnification: 10,000) showing the particle structure of tetragonal rectangular parallelepiped barium titanate produced according to Example 17.

FIG. 6 is an electron micrograph (magnification: 20,000) showing the particle structure of tetragonal rectangular parallelepiped barium titanate produced according to Example 17.

FIG. 7 is an electron micrograph (magnification: 30,000) showing the particle structure of cubic spherical barium titanate produced according to Example 20.

8 is an electron micrograph (magnification: 50,000) showing the particle structure of barium titanate produced in Example 21. FIG.

FIG. 9 is an electron micrograph (magnification: 100,000 times) showing the particle structure of commercially available barium titanate produced by a wet method in Comparative Example 4.

FIG. 10 is an electron micrograph (magnification: 10,000) showing the particle structure of a commercially available tetragonal barium titanate produced by the solid phase method of Comparative Example 5.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Kinugasa 1-47, Funamachi, Taisho-ku, Osaka City Inside Takeka Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 23/00

Claims (11)

(57) [Claims] 1. A truly spherical barium titanate having a particle diameter of 0.2 to 5 μm, comprising primary particles of a particle diameter of 0.005 to 0.1 μm. However, the particle diameter of the primary particles is 1/3 or less of the particle diameter of the truly spherical barium titanate. 2. A spherical barium titanate obtained by calcining the true spherical barium titanate according to claim 1. 3. A tetragonal barium titanate obtained by calcining the true spherical barium titanate according to claim 1. 4. A spherical barium titanate obtained by hydrothermally reacting the true spherical barium titanate according to claim 1 under pressure. 5. A spherical barium titanate having a particle diameter of 0.2 to 5 μm, containing particles of different particle diameters or particles of different composition inside. 6. The method for producing barium titanate according to claim 1, wherein the titanium compound and the barium compound are subjected to a wet reaction by adding hydrogen peroxide. 7. The titanium compound is titanium hydroxide or titanium oxide, the barium compound is barium hydroxide, and a mixture of titanium hydroxide or titanium oxide and hydrogen peroxide is provided.
7. The method for producing barium titanate according to claim 6, wherein a wet reaction is performed with barium hydroxide under normal pressure. 8. The concentration of the titanium compound is 0.01 to 2.5 mol / l in terms of titanium oxide, the molar ratio of barium to titanium is 0.8 to 10, and the molar ratio of hydrogen peroxide to the titanium compound is The method for producing spherical barium titanate according to claim 7, wherein the aging reaction temperature is 0.1 to 10 and the aging reaction temperature is 40 to 100 ° C. 9. An aging reaction for at least 0.1 hour between a temperature at which the reaction is completed in 4 hours and a temperature 50 ° C. lower than the temperature, and then a reaction at a temperature at which the reaction is completed in 4 hours or more. A method for producing a spherical barium titanate according to claim 7, characterized in that: 10. A method for producing spherical barium titanate having a particle diameter of 0.2 to 5 μm, wherein the spherical barium titanate according to claim 1 is hydrothermally reacted under pressure. 11. The spherical spherical barium titanate according to claim 1, wherein the molar ratio of barium to titanium is 0.95 to 1.
A method for producing tetragonal barium titanate, wherein the temperature is adjusted to 05 and calcined at 900 to 1300 ° C.