JPH05330824A - Barium titanate and its production - Google Patents

Abstract

PURPOSE:To obtain perfectly spherical barium titanate having high dispersibility while controlling the particle diameter in accordance with the purpose for which the barium titanate is used. CONSTITUTION:When a titanium compd. and a barium compd. are brought into a hydrothermal reaction to produce barium titanate, perfectly spherical barium titanate having 0.2-5mum particle diameter composed of primary particles having 0.005-0.1mum particle diameter is produced by adding hydrogen peroxide. Cubic barium titanate or tetragonal barium titanate is obtd. by calcining the resulting perfectly spherical barium titanate. Perfectly spherical denser barium titanate is obtd. by bringing the resulting perfectly spherical barium titanate into a hydrothermal reaction under pressure.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION 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 for capacitors, PT
It is used as a dielectric material for electronic parts such as C thermistors. Recently, it has been required that the particle size of barium titanate can be controlled according to the purpose and that it has high dispersibility. It started to come.

For example, regarding a capacitor, in order to obtain a high dielectric constant type capacitor having good 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 to the inside of the grain. However, in order to obtain good characteristics, the grain size of the ceramic should be 0. It is necessary that the particle diameter is 5 to 1 μm and the particle diameters are uniform. In order to obtain such a ceramic, barium titanate as a raw material is also required to have a particle size of 0.5 to 1 μm and a narrow particle size distribution.

Further, in the high dielectric constant type multilayer capacitor, the dielectric ceramic layer is made thin to improve the capacity of the capacitor and downsize the capacitor, but in this case as well, the ceramic having good withstand voltage characteristics is used. In order to obtain a layer, barium titanate having a particle size of 0.2 to 1 μm and a narrow particle size distribution and good dispersibility is required.

Further, a semiconductor capacitor, a PTC thermistor having a positive temperature characteristic, and the like are devices that utilize the electrical characteristics of the grain boundaries of ceramics. Among these, those with good characteristics have a uniform grain boundary layer thickness. It is said that the particles have a uniform particle size. Therefore,
Also in these devices, in order to obtain good characteristics, barium titanate used as a raw material must have a particle size of 1 to 5 μm and a narrow particle size distribution.

However, the barium titanate produced by the conventional methods has not been able to sufficiently meet the above requirements.

That is, in the conventional method for producing barium titanate, barium titanate was produced by mixing and firing a titanium compound and a barium compound to cause a solid-phase reaction. In the case of reaction, the particle size of the obtained barium titanate is large due to the fact that the reaction is carried out at high temperature, the particle size does not become small even by mechanical pulverization, and the particle size distribution is wide, so that the particle size control However, since the shape was not constant, the dispersibility was poor, and it was impossible to meet the above requirements.

To solve this problem, it has been proposed to manufacture 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 particles of barium titanate can be obtained, and in addition, particles having a distorted particle shape, particles having particles associated with each other, and the like are produced. Therefore, even with these methods, it was not possible to obtain barium titanate having a desired particle size and a good dispersibility in the range of 0.2 μm to 5 μm.

Further, the barium titanate used for the core-shell sintered body must be of the tetragonal type, but when the tetragonal barium titanate obtained by the solid phase method is calcined, it can be obtained by the wet method. Even when the obtained pseudo-cubic barium titanate is calcined to obtain tetragonal barium titanate, the growth of the particles occurs unevenly and the sintering between the particles is intense, resulting in a wide particle size distribution. However, I was not able to meet the above demand at all.

[0011]

As described above, the conventional barium titanate cannot control the particle size sufficiently, and the dispersibility is poor.
There has been a problem that it is not possible to fully meet the demands for miniaturization and high performance of electronic parts such as C thermistors.

Therefore, it is an object of the present invention to provide barium titanate which can be controlled to have a particle diameter suitable for the purpose and has high dispersibility.

[0013]

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. In that case, by using hydrogen peroxide, it was found that a spherical barium titanate in which the particle size can be arbitrarily controlled can be obtained, whereby the above object can be easily achieved, and the present invention has been completed. Came to do.

That is, the barium titanate of the present invention is
A true 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 tightly agglomerated and bonded to each other in a spherical shape. Barium titanate is obtained by wet-reacting a titanium compound and a barium compound with hydrogen peroxide.

In the wet reaction between the titanium compound and the barium compound, hydrogen peroxide slowly advances the reaction for producing barium titanate, which has a particle shape of 0.005.
It is considered that this is a factor for producing a true spherical barium titanate having a particle size of 0.2 to 5 μm in which primary particles of 0.1 μm barium titanate are aggregated in a true spherical shape and having a narrow particle size distribution.

In this spherical spherical barium titanate, the primary particles of barium titanate are strongly agglomerated and bonded, and the barium titanate does not collapse during the handling operation during the production of electronic parts such as capacitors and PTC thermistors. It is considered that not only the primary particles of barium titanate are physically aggregated but also a kind of chemical bond is generated.

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 it is as a raw material for electronic parts such as capacitors and PTC thermistors, that is, as a raw material for electroceramics. Can be changed to cubic or tetragonal to provide a more preferable electroceramic raw material in which the particle shape and grain boundaries of the ceramic can be controlled more easily.

That is, the above-mentioned true spherical barium titanate changes its crystal form from pseudo-cubic to cubic or tetragonal by calcining at 600 ° C. or higher, and the crystallinity is good, and as described above, It becomes easier to control the particle size and grain boundaries, but these cubic or tetragonal barium titanates are literally spherical spherical barium titanate before calcination, and there are few contact points between particles. Therefore, there is little sintering due to calcination, and the particle size of the spherical barium titanate before calcination is almost maintained,
The particle size distribution is narrow and the dispersibility is excellent.

When the above-mentioned spherical barium titanate is reacted again under pressure (hydrothermal reaction), a denser spherical barium titanate can be obtained, which makes it easier to control the particle diameter and grain boundaries of ceramics. Can be

Further, in the present invention, in the production of true spherical barium titanate, as crystal nuclei, barium titanate particles having a particle size smaller than the particle size of the true spherical barium titanate to be produced or other perovskite type compounds. By incorporating particles, it is possible to obtain a true spherical barium titanate containing particles having different particle diameters or particles having different composition.

The particles having different particle diameters or particles having different composition contained in the true spherical barium titanate promote the improvement of the electrical characteristics of the ceramics and the improvement of the crystallinity of the particles by firing or calcination. Therefore, it becomes a factor for further improving the characteristics of the spherical barium titanate.

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

Regarding [Reaction Raw Material] In the present invention, a titanium compound and a barium compound are used as a reaction raw material, and hydrogen peroxide is used during the reaction. Therefore, the titanium compound, the barium compound, and the hydrogen peroxide will be described in this order.

The titanium compound can be used without any particular limitation as long as it produces a barium compound and a perovskite-type barium titanate, but it can be partially dissolved in an aqueous solution of hydrogen peroxide, or Alternatively, it is preferably completely dissolved, and it is preferable to contain as little as possible a component that mixes with the produced barium titanate and deteriorates its properties.

From the above viewpoints, examples of preferable titanium compounds include inorganic titanium compounds such as titanium oxide and titanium hydroxide, and organic titanium compounds such as titanium oxalate and titanium alkoxide.

Industrially, titanium oxide and titanium hydroxide, which are easily available, are often used. When using titanium hydroxide, the ignition loss is measured to determine the weight of titanium oxide (TiO ₂ ) in the titanium hydroxide, and the weight of titanium oxide is used as a reference for the amount ratio in the wet reaction with the barium compound. It is preferable from a practical point of view. When measuring the loss on ignition, it is suitable to use heating at 1000 ° C. for 2 hours as a reference.

The barium compound can be used without any particular limitation as long as it reacts with the above titanium compound to form a perovskite type barium titanate, but a basic barium compound is usually used. To be done.

Further, it is preferable to contain as little as possible a component that mixes with the produced barium titanate and deteriorates its characteristics. From this point of view, preferable barium compounds include, for example, barium hydroxide and barium oxide. , Barium alkoxide and the like.

Various types of hydrogen peroxide can be used without any particular limitation, but usually 30% (% by weight, the same applies hereinafter) commercially available peroxide due to easy availability and handling. Hydrogen water, 35% hydrogen peroxide water, 50% hydrogen peroxide water, 60% hydrogen peroxide water, etc. are used.

Regarding [Reaction Method] There is no particular limitation on the order of addition of these titanium compound, barium compound and hydrogen peroxide, but unless the reaction is carried out in a dilute concentration, the titanium compound is added before addition of the barium compound. It is preferable to react by mixing with hydrogen peroxide. That is, unless hydrogen peroxide is added to a system in which a barium compound is present, except for the case of reacting in a dilute concentration, sparingly soluble barium oxide (BaO ₂ ) is generated and precipitates, which cannot be used in the reaction. is there.

The amount of hydrogen peroxide used is 0.1 to 0.1 in terms of molar ratio of hydrogen peroxide to titanium compound (converted to titanium oxide), that is, H ₂ O ₂ / TiO ₂ (molar ratio).
10 is preferable.

Even if the amount of hydrogen peroxide used exceeds the above titanium compound in a molar ratio of 10 or more, the effect is not increased, and only decomposes upon reaction with the titanium compound, which is uneconomical. Further, when the amount of hydrogen peroxide is less than 0.1 in terms of molar ratio with respect to the titanium compound, the effect of adding hydrogen peroxide cannot be sufficiently obtained.

When a titanium compound and hydrogen peroxide are mixed, they usually react with each other to form titanium peroxide, which causes yellowing. 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 solution of titanium peroxide.

For example, in the case where the titanium oxide conversion concentration in the titanium hydroxide slurry is as thin as about 0.05 to 0.25 mol / l, if hydrogen peroxide is mixed at a molar ratio of 3 times or more, the titanium peroxide will be oxidized. It becomes a completely dissolved aqueous solution of the substance.

However, when the concentration 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 should be adjusted. Even if changed, it does not become a completely dissolved aqueous solution but a suspension solution. However, there is no problem in producing a true spherical barium titanate, whether it is a completely dissolved aqueous solution of titanium peroxide as described above or a suspension solution.

The temperature at the time of mixing hydrogen peroxide may be room temperature, but in order to obtain a homogeneous completely dissolved aqueous solution or suspension solution of titanium peroxide in a relatively short time, 40 to 100 ° C.
It is preferable to heat to.

The titanium oxide equivalent concentration of the titanium compound is 0.01-2. With the barium compound added.
5 mol / l, especially 0.06-1 mol / l is preferred. If the concentration exceeds 2.5 mol / l, the viscosity becomes high and it becomes difficult to stir, and barium titanate obtained by reacting with the barium compound has a nonuniform particle size. If the concentration is lower than 0.01 mol / l, the reaction rate will be significantly reduced.

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

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

At this time, the titanium compound and the barium compound react with each other to form pseudo-cubic perovskite type barium titanate, but the particle size of the primary particles is 0.005 to 0.005.
In order to obtain a true spherical barium titanate having a secondary particle size of 0.1 to 5 μm and a particle diameter of 0.2 to 5 μm, the barium titanate production reaction is not completed within 1 hour, preferably within 4 hours. So that the molar ratio of titanium and barium,
It is preferable to set the concentration of the barium compound, the reaction temperature and the like.

In order to make the particle diameters of the obtained spherical barium titanate uniform and narrow the particle size distribution, it is preferable to mix the titanium compound and the barium compound at a temperature below 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 from the temperature.
0.1 ° C., preferably between the temperature at which the reaction is completed in 4 hours and 40 ° C. below that temperature.
It is preferable to perform the aging reaction for not less than time, preferably not less than 1 hour. After the aging reaction, it is preferable to complete the reaction by reacting at a temperature not lower than 4 hours. The completion of the above 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 carried out under normal pressure or reduced pressure. For example, when this aging reaction is carried out under pressure using a closed container, the obtained barium titanate is likely to be fine particles of 0.1 μm or less, and even when it is 0.2 μm or more, non-spherical particles are introduced. Has a wide particle size distribution, and has a particle size distribution of 0.
No true spherical barium titanate of 2 to 5 μm can be obtained. This tendency becomes remarkable especially when the 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 the components such as carbon dioxide in the air.

As described above, the particle size is 0.005 to 0.005.
Particle diameter composed of primary particles of 0.1 μm 0.2 to 5 μm
m spherical spherical barium titanate is obtained, but in the present invention, the particle size of the primary particles is spherical between the particle size of the primary particles and the particle size of the spherical spherical barium titanate that is the secondary particle. The requirement is 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 a secondary particle, the spherical property is impaired and the barium spherical titanate having good dispersibility cannot be obtained. Is. In particular, the particle size of the primary particles is preferably ⅕ or less of the particle size of the spherical barium titanate.

Further, in the present invention, the particle size of the true spherical barium titanate is specified to be 0.2 to 5 μm.
This is due to the following reasons. That is, if the particle size is smaller than 0.2 μm, the dispersibility is poor, and for example, the dispersibility in the binder is poor during the molding before being made into ceramic, and it is difficult to obtain a uniform molded body. Also, the particle size is 5
If it is larger than μm, it becomes impossible to adapt to the trend of thinning and miniaturizing electronic ceramic parts such as capacitors and PTC thermistors.

Further, in the present invention, the particle size of the primary particles is required to be 0.005 to 0.1 μm, but this is due to the following reason. That is, particles having a primary particle size of less than 0.005 μm cannot be obtained by the wet method, and when the primary particle size is greater than 0.1 μm, the temperature during firing or calcination increases, resulting in less dispersibility with sintering. It becomes difficult to obtain good barium titanate.

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

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

First, the influence of the concentration of the solution on the particle diameter and particle shape of barium titanate particles will be described with reference to the above reaction example.

The higher the solution concentration, especially the barium ion concentration, the smaller the particle size tends to be.

In this reaction example, assuming that Ba / Ti (molar ratio) = 1.4 is constant, if the titanium oxide conversion concentration in the solution becomes higher than 0.312 mol / l, the barium ion concentration is accordingly increased. As a result, the particle size of barium titanate becomes smaller than 1 μm in the above reaction example. On the contrary, when the titanium oxide equivalent concentration becomes lower than 0.312 mol / l, the barium ion concentration decreases accordingly, so that the particle diameter becomes larger than 1 μm.

Regarding the reaction temperature of 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 solution of titanium peroxide. At this time, the titanium compound slurry and hydrogen peroxide are mixed. And then mix the solution with 20 to 1
Aging at 00 ° C. As the aging temperature increases, the particle size decreases, and when the aging temperature decreases, the particle size increases.

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

In the above reaction example, the amount of the barium compound is Ba / Ti (molar ratio) = 1.4, but if it is more than that, the barium ion concentration increases, the reaction rate becomes faster, and the particle shape becomes No change, but the particle size becomes smaller.
However, for example, in the presence of an extremely excessive barium ion having a Ba / Ti (molar ratio) of more than 10, barium titanate is no longer an agglomerate and fine particles are formed.

When the amount of barium hydroxide is less 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, in the presence of too little barium ions, for example Ba / Ti (molar ratio) of less than 0.8, the reaction itself no longer occurs.

However, even if the Ba / Ti (molar ratio) is temporarily less than 0.8, the Ba / Ti ratio is not reached by the end of the reaction.
If the (molar ratio) is 0.8 or more, true spherical barium titanate can be produced.

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 long time near the temperature at which the titanium compound and the barium compound start to react to form barium titanate. .. Further, the higher the aging reaction temperature, the smaller the particle size.

For example, the aging reaction is performed at a temperature lower than 70 ° C., for example, the aging reaction is performed at 50 ° C. for 2 hours, and the aging reaction is performed at a temperature at which the reaction rate becomes extremely slow.
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 1
Similar to barium titanate obtained by aging reaction at 00 ° C., it has a spherical shape with an average particle size of 0.6 μm. That is,
The aging reaction at a low temperature at which the reaction does not proceed is meaningless with or without the same result.

When the aging reaction is performed at a temperature higher than 70 ° C., the reaction rate increases and the particle shape does not change, but the particle size decreases. For example, use a closed container and set the aging reaction temperature to 1
If the temperature is raised to about 80 ° C, the reaction speed becomes too fast,
The particle shape that forms aggregates can no longer be maintained, and the obtained barium titanate becomes fine particles.

Further, the aging reaction temperature is lowered and the aging reaction time is made longer than in the case of the above reaction example, and the aging reaction temperature is changed from 60 ° C. to 70 ° C.
After the temperature was raised to 0 ° C over 10 hours to allow the aging reaction, 10
When the reaction is completed at 0 ° C. for 4 hours, the obtained barium titanate has a larger particle size than in the above reaction example, and the average particle size is 2.5 μm.

By the reaction raw material and the reaction method as described above, spherical barium titanate having a narrow particle size distribution and having a particle size of 0.2 to 5 μm and composed of primary particles having a particle size of 0.005 to 0.1 μm can be obtained. ..

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

Since the above-mentioned true spherical barium titanate has a true spherical shape, it has excellent dispersibility, and by selecting the aging reaction temperature, the concentration of the titanium compound, Ba / Ti (molar ratio) and the like. Since its particle size can be controlled arbitrarily, it is possible to control the particle size according to the purpose with the miniaturization and high performance of electronic parts such as capacitors and PTC thermistors, and with high dispersibility. It can fully meet the demands of being there.

Next, the particle diameter is 0.005 to 0.1 μm.
of spherical spherical barium titanate of 0.2 to 5 μm composed of primary particles [cubic barium titanate and tetragonal barium titanate obtained by calcination], the particle size of 0.
0.2 to 5 composed of primary particles of 005 to 0.1 μm
[Compact spherical barium titanate obtained by reacting again under pressure with true spherical barium titanate] and the present invention was applied to [spherical titanic acid containing particles of different particle shape or particles of different composition] Barium] will be described.

[ Cubic crystalline titanate obtained by calcination
The true spherical barium titanate obtained by the present invention 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.

Then, when this is calcined at 600 ° C. or higher, the crystal form changes to cubic or tetragonal, and the crystallinity is good, and barium titanate in which the grain size and grain boundaries of ceramics can be controlled more easily can be obtained. ..

For example, this spherical barium titanate is added to 6
When calcined at 00 to 1100 ° C., cubic or tetragonal spherical barium titanate having good dispersibility and maintaining the particle size and shape of true spherical barium titanate can be obtained.

When calcination is performed at 900 to 1300 ° C.,
Tetragonal barium titanate is obtained. In this case, if the temperature is low and the particle size is large, it becomes spherical. If the particle size is small or calcination is performed at a high temperature, a rectangular parallelepiped single crystal powder is obtained.

By the above-described calcination, barium titanate becomes high-density and has good crystallinity, and when it is made into ceramics, it becomes an electroceramic raw material in which the particle diameter and grain boundaries can be more easily controlled.

The cubic barium titanate and the tetragonal barium titanate have a true spherical barium titanate shape which is literally a spherical shape before calcination, and the number of contact points between the particles is small. 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 size according to the purpose which is the characteristic of the true spherical barium titanate before calcination, and have a high dispersion. It retains the property of being effective and is more useful than a barium titanate obtained by a conventional wet method that is calcined.

[ Dense reaction obtained by reacting again under pressure
True spherical barium titanate] Particle diameter of the present invention 0.005
Reaction of 0.2-5 μm true spherical barium titanate composed of 0.1 μm primary particles again under pressure (hydrothermal reaction)
By doing so, a denser spherical barium titanate can be obtained.

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

When the barium compound is added during the hydrothermal reaction under pressure, it has the effect of promoting the growth of primary particles. The true spherical barium titanate in which such primary particles have grown is a suitable raw material for obtaining a ceramic in which an additive is arranged at grain boundaries.

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

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

[ Particles with different particle diameters or particles with different composition are
True spherical barium titanate contained] Further, by applying the method of the present invention, it is possible to produce a true spherical barium titanate containing particles of different particle sizes or particles of different composition inside.

For example, tetragonal barium titanate having good crystallinity and having a particle size of 0.1 μm or more and smaller than the particle size of target particles is used. By applying the above method, a true spherical barium titanate containing tetragonal barium titanate particles having different particle sizes can be produced. Then, by calcination of the true spherical barium titanate containing tetragonal barium titanate particles therein, tetragonal rectangular parallelepiped barium titanate can be obtained more easily.

In addition, the high temperature sinterability of strontium titanate, barium zirconate, barium zirconate titanate and the like having a particle size smaller than the particle size of the target particles to be produced improves the electrical characteristics of capacitors, PTC thermistors and the like. Using the contributing perovskite compound as a crystal nucleus, the method of the present invention can be applied to produce a true spherical barium titanate containing different composition particles such as strontium titanate, barium zirconate, and barium zirconate titanate. it can.

By firing the true spherical barium titanate containing the different composition particles therein, the different composition particles forming the crystal nuclei and the barium titanate can be reacted at low temperature. This makes it possible to improve the electrical properties of barium titanate based on the high-temperature sinterable heterogeneous composition particles by low-temperature sintering.

The true spherical barium titanate containing these particles having different particle diameters or particles having different composition therein can be obtained by the solid phase method with different crystal particle diameters or different composition particles, or by the wet method. The particles of good crystallinity having different particle diameters or different composition obtained by calcining the obtained particles are converted into titanium alkoxide, an aqueous solution of titanium salt, or titanium hydroxide, titanium oxide or the like obtained by hydrolyzing these. It is obtained by adding and mixing, and then mixing and reacting hydrogen peroxide and a barium compound.

Thus, the true spherical barium titanate containing particles of different particle size or particles of different composition obtained by applying the method of the present invention has a narrow particle size distribution and high dispersibility of the present invention. It combines the features of true spherical barium titanate.

Hydrogen peroxide may be added directly to an aqueous solution of titanium alkoxide or titanium salt in the production of a true spherical barium titanate containing particles of different particle size or particles of different composition inside. It may be added after their hydrolysis. That is, before the barium compound is mixed and reacted, the barium compound may be added and mixed at any stage.

Mixing of particles having different particle diameters or particles having different composition is
It is preferably carried out before the hydrolysis of the aqueous solution of titanium alkoxide or titanium salt. This is because it is added before hydrolysis, and titanium hydroxide is attached to the surface of these particles by hydrolysis, and by reaction with the barium compound, those particles with different particle diameters or particles with different composition surely become titanium oxide. This is because it can be taken inside the barium. Further, it is preferable that the particles having different particle diameters and the particles having different composition are sufficiently dispersed by a wet method before mixing.

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

[0089]

INDUSTRIAL APPLICABILITY The true spherical barium titanate of the present invention can control the particle size according to the purpose, and is true spherical and has excellent dispersibility.

Therefore, the true spherical barium titanate of the present invention has been required for barium titanate as electronic components such as capacitors, PTC thermistors, and piezoelectric bodies have become smaller and have higher performance. It is possible to sufficiently meet the demand that "the particle size can be controlled according to the above-mentioned condition and that the dispersibility is high."

The true spherical barium titanate of the present invention can be used as it is as a raw material for electronic parts such as the above-mentioned capacitors and PTC thermistors. However, if the true spherical barium titanate of the present invention is calcined, sintering will occur. It is possible to obtain cubic spherical barium titanate or tetragonal spherical barium titanate having a narrow particle size distribution and maintaining the particle size and shape of true spherical barium titanate before calcination and having high dispersibility.

These spherical barium titanates are compared with barium titanates obtained by the conventional solid phase method or wet method.
Since the particle size distribution is narrow and spherical, the amount of air entrained at the time of molding is small, so the occurrence of lamination is suppressed, and it becomes possible to obtain a uniform and high-density molded body. The final density is also greatly improved.

Therefore, by using the spherical barium titanate, it is possible to obtain a capacitor having a uniform particle size and excellent dielectric characteristics. Further, by calcination of the spherical spherical barium titanate at a high temperature, it is possible to obtain a tetragonal rectangular parallelepiped barium titanate with less sintering and a narrow particle size distribution.

This tetragonal rectangular parallelepiped barium titanate is
Since it is a high-density barium titanate that is tighter than the spherical barium titanate, it is easier to strictly control the particle size and the grain boundary of the ceramics. By using it, it is possible to obtain a capacitor, a PTC thermistor, or the like having more excellent dielectric characteristics.

Further, by calcination of a true spherical barium titanate containing tetragonal barium titanate having different particle sizes inside, it is possible to more easily obtain a tetragonal rectangular parallelepiped barium titanate having a uniform particle size. Therefore, it is possible to more easily obtain the above-described capacitor, PTC thermistor, etc. having excellent dielectric characteristics.

Also, by firing a true spherical barium titanate containing high-temperature sinterable different composition particles such as strontium titanate, barium zirconate, and barium zirconate titanate, the composition different from barium titanate is obtained. It becomes possible to perform low temperature sintering while reacting with the particles, and it is possible to more easily improve the electrical characteristics of the capacitor, the PTC thermistor, and the like.

[0097]

EXAMPLES 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.)
(6, 4% content) is hydrolyzed with 5% ammonia water, the obtained titanium hydroxide gel is filtered and washed with water, and the titanium hydroxide cake [I having a titanium oxide concentration of 12.3% by weight calculated by ignition loss] [I ]

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

The resulting slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution [II]. This suspension solution was cooled to 40 ° C. by natural cooling, and 136 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.
4] is added and 0.5 is added to 100 ° C. while flowing nitrogen.
The temperature was raised over time, and the reaction was carried out for 4 hours under reflux.

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

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

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

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

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.69 to 1.03 μm, and the particle size distribution is narrow,
The average particle diameter was 0.86 μm.

Example 3 200 g of titanium hydroxide cake [I] prepared in Example 1
In an aqueous solution in which 751 g of water are evenly dispersed, 82 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO ₂ (molar ratio) = 2.
35] was added, and the titanium oxide concentration was 0.3% as in Example 1.
A 312 mol / l slurry was obtained.

The resulting slurry was uniformly mixed at 60 ° C. for 2 hours to obtain a suspension solution. After cooling the suspension to 40 ° C., 136 g of barium hydroxide octahydrate
[Ba / Ti (molar ratio) = 1.4] was added, the temperature was raised to 100 ° C. in 0.5 hours while flowing nitrogen, and the mixture was reacted for 4 hours while refluxing.

The obtained barium titanate had a particle size of 0.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.58 to 0.70 μm, and the particle size distribution is narrow,
The average particle diameter was 0.64 μm.

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

The resulting slurry was uniformly mixed at 20 ° C. for 2 hours to obtain a suspension solution [III]. To this suspension solution, 116 g of barium hydroxide octahydrate [Ba / Ti (molar ratio)
= 1.2] is added to 0.75 from 20 ° C to 100 ° C.
The temperature was raised over time, and the reaction was carried out for 4 hours under reflux.

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.27 to 0.43 μm, and the particle size distribution is narrow,
The average particle diameter was 0.35 μm.

FIG. 2 is an electron micrograph showing the particle structure of the true spherical barium titanate produced in Example 4 at a magnification of 30,000, and FIG. 3 is the true spherical titanate produced in Example 4. It is an electron micrograph showing the grain structure of barium at a magnification of 100,000 times.

It can be seen that the true spherical barium titanate of Example 4 has a high true spherical property in the particle shape even when it is magnified 100,000 times, and the particle diameter thereof is almost uniform, so that the particle size distribution is narrow.

Example 5 To the same suspension solution [III] as that prepared in Example 4, 194 g of barium hydroxide octahydrate [Ba / Ti (molar ratio) = 2.0] was added, and then, Barium titanate was obtained in the same manner as in Example 4.

The barium titanate obtained had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.15 to 0.25 μm, and the particle size distribution is narrow,
The average particle diameter was 0.20 μm.

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

The resulting slurry was uniformly mixed at 20 ° C. for 2 hours to obtain a completely dissolved aqueous solution of titanium peroxide. 194 g of barium hydroxide octahydrate in this aqueous solution [Ba / T
i (molar ratio) = 4.0], and added from 20 ° C. to 100 ° C.
The temperature was raised to 0.75 hours, and the mixture was reacted under reflux for 4 hours.

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.45 to 0.83 μm, and the particle size distribution is narrow,
The average particle diameter was 0.64 μm.

Example 7 2 was added to the same suspension solution [II] as that prepared in Example 1.
136 g of barium hydroxide / octahydrate at 0 ° C [Ba / Ti
(Molar ratio) = 1.4] was added, the temperature was raised to 60 ° C. in 0.25 hours, and an aging reaction was performed at 60 ° C. for 3 hours, and then 100 ° C.
The temperature was raised to 0.5 hours, and the mixture was reacted at 100 ° C. under reflux for 4 hours.

The barium titanate obtained had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.77 μm, and the particle size distribution is narrow,
The average particle diameter was 0.70 μm.

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

The barium titanate obtained had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 1.22 to 1.82 μm, and the particle size distribution is narrow,
The average particle diameter 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 reaction at 80 ° C. for 3 hours, Furthermore, 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. under reflux for 6 hours.
The total amount of barium hydroxide / octahydrate added was 138 g,
This is the molar ratio of barium to titanium, ie [Ba
/ Ti (molar ratio)] corresponds to 1.4.

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 03 to 0.1 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.34 to 0.62 μm, the particle size distribution is narrow, and the average particle diameter is 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, the temperature was raised to 80 ° C. in 0.5 hour with nitrogen flow, the reaction was aged for 2 hours, and then 49 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 0.5] was added. After the addition, the temperature was immediately raised to 100 ° C. and the reaction was carried out under reflux for 4 hours.

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles having a particle size of 03 to 0.1 μm, and has a 90% number distribution particle size of 0.63 to 0.77 μm as observed by an electron microscope, and has a narrow particle size distribution and an average particle size of It was 0.70 μm.

Comparative Example 1 200 g of the titanium hydroxide cake [I] prepared in Example 1
Is uniformly dispersed with 809 g of water, and the titanium oxide concentration is 0.3
12 mol / l, and 136 g of barium hydroxide / octahydrate [Ba / Ti (molar ratio) = 1.4] was added to this aqueous solution.
C., the temperature was raised to 60.degree. C. in 0.25 hours while flowing nitrogen, and the reaction was aged at 60.degree. C. for 3 hours, and then 100.degree.
Up to 0.25 hours and reflux at 100 ° C for 4
Reacted for hours.

The barium titanate thus obtained is a true spherical agglomerate composed of primary particles having a particle diameter of 0.01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation. Was 0.14 to 0.42 μm, and the average particle size was 0.28 μm, but the particle size was not constant, and the shape was distorted and far from a true sphere.

FIG. 4 is an electron micrograph showing the grain structure of barium titanate produced in Comparative Example 1 at a magnification of 30,000. As shown in FIG. 4, the barium titanate produced according to Comparative Example 1 had a nonuniform particle size, and the shape was distorted and far from a true sphere.

Comparative Example 2 200 g of the titanium hydroxide cake [I] produced in Example 1
Is uniformly dispersed in 809 g of water, and the concentration of titanium oxide is adjusted to 0.
It was set to 312 mol / l.

At 20 ° C., 136 g of barium hydroxide / octahydrate (Ba / Ti (molar ratio) = 1.4) was added to this aqueous solution, and the temperature was raised to 100 ° C. in 0.5 hours while flowing nitrogen, The mixture was reacted at 100 ° C under reflux for 4 hours.

The barium titanate obtained had a particle size of 0.
It is an aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter is 0.08 to 0.16 μm and its average particle diameter is 0.12.
It was μm, but the shape was distorted and far from a true sphere.

Example 11 The same suspension solution [II] as that prepared in Example 1 was added to
136 g of barium hydroxide / octahydrate at 0 ° C [Ba / Ti
(Molar ratio) = 1.4], and 0.75 up to 100 ° C.
The temperature was raised at a constant rate over a period of time, and the reaction was aged at 100 ° C. for 4 hours under normal pressure, then 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.
It is a true spherical agglomerate composed of primary particles of 05 to 0.1 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.77 μm, the particle size distribution is narrow, and the average particle diameter is It was 0.70 μm. In addition, this aggregate was extremely dense.

Example 12 The same suspension solution [II] as that prepared in Example 1 was added to
136 g of barium hydroxide / octahydrate at 0 ° C [Ba / Ti
(Molar ratio) = 1.4], and 0.75 up to 100 ° C.
The temperature was raised over time, and then the reaction was carried out 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. To this slurry, 200 g of barium hydroxide / octahydrate was added and mixed, and then placed in a closed container, The temperature was raised to 180 ° C. in 1 hour, and then reacted at 180 ° C. for 4 hours.

The obtained barium titanate had a particle size of 0.
It is a true spherical agglomerate composed of primary particles of 05 to 0.1 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.77 μm, the particle size distribution is narrow, and the average particle diameter is It was 0.70 μm.

Example 13 500 g of titanium tetrachloride aqueous solution (containing 16.4% of titanium)
After adding 410 g of urea and 4000 g of water to and mixing them,
The temperature was raised and hydrolysis was carried out for 4 hours while refluxing to obtain a slurry of fine particulate hydrous 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% by weight calculated by loss on ignition.

This anatase type hydrous titanium oxide cake 2
To an aqueous solution prepared by uniformly dispersing 00 g with 1228 g of water,
% Hydrogen peroxide water (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 calculated that 70% of 30% hydrogen peroxide solution was water.

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

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.77 μm, and the particle size distribution is narrow,
The average particle diameter was 0.70 μm.

Example 14 500 g of titanium tetrachloride aqueous solution (containing 16.4% of titanium)
Water 3904g and 30% hydrogen peroxide water 137g [H ₂ O
₂ / TiO ₂ (molar ratio) = 2.35] was added and mixed uniformly for 2 hours, then hydrolyzed with aqueous ammonia, and the obtained titanium hydroxide was filtered and washed with water, and converted by loss on ignition. 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 an aqueous solution uniformly dispersed in 6 g, 43 g of 30% hydrogen peroxide solution [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 resulting 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.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.77 μm, and the particle size distribution is narrow,
The average particle diameter was 0.70 μm.

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

159 g of barium hydroxide / octahydrate (Ba / Ti (molar ratio) = 1.4) was added to the resulting suspension solution at 20 ° C.
Was gradually added, 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.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.44 to 0.60 μm, and the particle size distribution is narrow.
The average particle diameter was 0.52 μm.

Example 16 The spherical barium titanate having an average particle size 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 temperature was raised at 10 ° C., 10 ml of acetic acid was added to adjust the pH to 8.50, the mixture was stirred at 60 ° C. for 1 hour, filtered, and then 3000 g
It was washed with water and dried.

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

The obtained barium titanate powder was crushed for 1 hour with a mulcher and calcined at 1000 ° C.

The barium titanate obtained by the above calcination is dense, has no sintering, and has a 90% number distribution particle diameter of 0.49 to 0.91 μm as observed by an electron microscope.
It was tetragonal rectangular parallelepiped barium titanate having an average particle size of 0.70 μm.

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

The obtained powder is heated to 20 ° C. to 1100 ° C. 3
After heating at a constant rate for 2 hours and calcining at 1100 ° C for 2 hours, 2
The temperature was lowered to 0 ° C. at a constant rate for 3 hours.

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

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

Example 18 Yttrium nitrate having a yttrium content of 1% relative to the weight of titanium contained was added to an aqueous titanium tetrachloride solution, followed by hydrolysis with aqueous ammonia, and the obtained yttrium-containing titanium hydroxide gel was filtered. -Washing with water gave a yttrium-containing titanium hydroxide cake having a titanium oxide concentration of 12.3% by weight calculated by loss on ignition.

200 g of the obtained yttrium-containing titanium hydroxide cake was uniformly dispersed in 654 g of water to prepare an aqueous solution.
221 g of 30% hydrogen peroxide solution [H ₂ O ₂ / TiO _2
2 (molar ratio) = 6.35] was added, and the same reaction as in Example 1 was performed.

The obtained barium titanate had a particle size of 0.
It is a true spherical aggregate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.63 to 0.94 μm, and the particle size distribution is narrow.
The average particle diameter was 0.78 μm.

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

The obtained barium titanate had a particle size of 0.
It is a true spherical agglomerate composed of primary particles of 01 to 0.03 μm, and its 90% number distribution particle diameter by electron microscope observation is 0.50 to 0.74 μm, and the particle size distribution is narrow,
The average particle diameter was 0.62 μm.

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

The barium titanate obtained by the above-mentioned calcination is cubic spherical barium titanate having an average particle size of 0.95 μm which does not have sintering and maintains the particle size before calcination. Barium acid had a narrow particle size distribution and excellent dispersibility.

FIG. 7 is an electron micrograph at a magnification of 30,000 showing the grain 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 size even when it was magnified 30,000 times.

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

Next, 144 g of urea was added and the temperature was increased to 20 ° C.
Up to 100 ° C for 0.5 hours at a constant rate, then 100 ° C
A thermal hydrolysis reaction was carried out under reflux for 4 hours.

After the reaction, filtration of the slurry and washing with water were repeated, 1200 g of water was added to the obtained barium titanate-containing titanium hydroxide cake, and the mixture was stirred, to which 302 g of barium hydroxide / octahydrate [Ba / Ti] was added. (Molar ratio) = 1.
4] was added, and the mixture was aged at 50 ° C. for 2 hours while flowing with nitrogen, and then reacted at reflux at 100 ° C. for 4 hours.

The obtained barium titanate had a particle size of 0.03 to 10 except for the tetragonal barium titanate contained therein.
It is a true spherical aggregate composed of primary particles of 0.1 μm, and this aggregate has excellent crystallinity and has a 90% number distribution particle diameter of 0.20 to 0.36 μm as observed by an electron microscope. The average particle size was narrow and was 0.28 μm.

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

Example 22 200 g of titanium tetrachloride aqueous solution (containing 16.4% of titanium)
After adding 600 g of water to the above and uniformly mixing for 1 hour, 80 g of tetragonal barium titanate having an average particle diameter of 0.8 μm was added and stirred for 3 hours to mix.

Next, the pH of the solution was adjusted to 7 with 5% ammonia water.
Is gradually added to the barium titanate-containing titanium hydroxide cake, 1000 g of water is 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 cooling the obtained slurry to 20 ° C., 302 g of barium hydroxide / octahydrate [Ba /
Ti (molar ratio) = 1.4] was added, the mixture was aged at 60 ° C. for 2 hours while flowing nitrogen, and then reacted at 100 ° C. under reflux for 4 hours.

The obtained barium titanate had a particle diameter of 0.03 to 10 except for the tetragonal barium titanate contained therein.
It is a true spherical agglomerate composed of 0.1 μm primary particles, and this agglomerate is excellent in crystallinity, has a 90% number distribution particle diameter of 0.78 to 1.06 μm by electron microscope observation, and has a particle size distribution. It was narrow and the average particle size was 0.92 μm.

Comparative Example 3 2 was added to the same suspension solution [II] as that prepared in Example 1.
136 g of barium hydroxide / octahydrate at 0 ° C [Ba / Ti
(Molar ratio) = 1.4] and added in a closed container at 180 ° C.
Up to 0.75 hours at a constant rate and then at 180 ° C for 4
Reacted for hours. The obtained barium titanate was fine particles having a particle diameter of 0.02 to 0.1 μm.

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

Next, 5% ammonium water was gradually added until the pH of the liquid 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 and stirred. Then, 200 g of 30% aqueous hydrogen peroxide [H ₂ O ₂ / TiO ₂ (molar ratio) =
2.58] was added, and the mixture was stirred at 60 ° C. for 2 hours.

After cooling the obtained slurry to 20 ° C., 302 g of barium hydroxide / octahydrate [Ba /
Ti (molar ratio) = 1.4] was added, the mixture was aged at 60 ° C. for 2 hours while flowing nitrogen, and then reacted at 100 ° C. under reflux for 4 hours.

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

Comparative Example 4 When a commercially available barium titanate produced by the wet method was observed with an electron microscope, its average particle diameter was 0.1.
The particle size was μm, the amount of sintering was large, and the particles were inhomogeneous particles with only depressed particles.

FIG. 9 is an electron micrograph showing the grain structure of barium titanate of Comparative Example 4 at a magnification of 100,000 times. As shown in FIG. 9, it is found that the barium titanate of Comparative Example 4 has a large amount of sintering and the particle shape is not uniform.

Comparative Example 5 When a commercially available barium titanate produced by the solid phase method was observed with an electron microscope, its average particle shape was 0.8.
The particle size was μm, the amount of sintering was large, and tetragonal barium titanate was used, but the particles had an indefinite shape and a wide particle size distribution.

FIG. 10 is an electron micrograph showing the grain structure of barium titanate of Comparative Example 5 at a magnification of 10,000 times. Comparison between this FIG. 10 and FIG. 5 (FIG. 5 is an electron micrograph at a magnification of 10,000 times showing the particle structure of tetragonal rectangular parallelepiped barium titanate produced according to Example 17 of the present invention) is clear. As described above, 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 has excellent characteristics in all respects such as lack of property.

[Brief description of drawings]

1 is an electron micrograph showing the particle structure of a true spherical barium titanate produced in Example 1 at a magnification of 30,000.

FIG. 2 is an electron micrograph at a magnification of 30,000 showing the particle structure of the true spherical barium titanate produced in Example 4.

3 is an electron micrograph showing a particle structure of a true spherical barium titanate produced in Example 4 at a magnification of 100,000. FIG.

4 is an electron micrograph at a magnification of 30,000 showing the particle structure of barium titanate produced in Comparative Example 1. FIG.

5 is an electron micrograph showing the grain structure of tetragonal rectangular parallelepiped barium titanate produced in Example 17 at a magnification of 10,000. FIG.

FIG. 6 is an electron micrograph at a magnification of 20,000 showing the particle structure of tetragonal rectangular parallelepiped barium titanate produced in Example 17.

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

FIG. 8 is an electron micrograph at a magnification of 50,000 showing the particle structure of a true spherical barium titanate produced in Example 21.

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

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

[Procedure amendment]

[Submission date] June 4, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

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Front Page Continuation (72) Inventor Masanori Kinugasa 1-347 Funamachi, Taisho-ku, Osaka

Claims (11)

[Claims] 1. A true spherical barium titanate having a particle diameter of 0.2 to 5 μm, which is composed of primary particles having a particle diameter of 0.005 to 0.1 μm. However, the particle diameter of the primary particles is ⅓ or less of the particle diameter of the true spherical barium titanate. 2. A spherical barium titanate obtained by calcination of the spherical spherical barium titanate according to claim 1. 3. 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, which contains particles having different particle diameters or particles having different composition therein. 6. The method for producing a true spherical barium titanate according to claim 1, wherein the titanium compound and the barium compound are wet-reacted by adding hydrogen peroxide. 7. The titanium compound is titanium hydroxide or titanium oxide, the barium compound is barium hydroxide, and titanium hydroxide or titanium oxide and hydrogen peroxide are mixed,
Thereafter, the wet reaction with barium hydroxide under normal pressure is carried out, and the method for producing a spherical barium titanate according to claim 6, which is characterized in that. 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 a 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. After aging reaction for 0.1 hour or more between a temperature at which the reaction is completed in 4 hours and a temperature lower than that temperature by 50 ° C., the reaction is performed at a temperature at which the reaction is completed or more. The method for producing a true spherical barium titanate according to claim 7. 10. A method for producing a true spherical barium titanate having a particle diameter of 0.2 to 5 μm, which comprises hydrothermally reacting the true spherical barium titanate according to claim 1. 11. The spherical spherical barium titanate according to claim 1 has a molar ratio of barium to titanium of 0.95 to 1.
A method for producing tetragonal barium titanate, which comprises adjusting to 05 and calcining at 900 to 1300 ° C.