JP5320568B2 - Method for producing fibrous barium titanate - Google Patents

Description

The present invention for the production method of the barium fibrous titanate, provides a method for producing a fibrous barium titanate having a very large specific surface area easily, efficiently.

In general, metal titanates such as barium titanate and strontium titanate are widely used for dielectric materials such as multilayer ceramic capacitors, semiconductor devices, and high-frequency filters.
When the amount of reaction per unit area of the dielectric material increases, for example, a multilayer ceramic capacitor can be reduced in size and increased in capacity. For this purpose, it is necessary to increase the specific surface area of the dielectric material as much as possible.
In general, in order to increase the specific surface area, it is conceivable first to make the metal titanate fine particles, but it is not easy to produce a metal having a specific surface area exceeding about 300 m ² / g, and the reproducibility is not good. There is a problem.

  For example, Patent Document 1 discloses that when a barium titanate powder is produced by a hydrothermal synthesis method using a titanium compound and a barium compound, the pH of the titanium compound is controlled in the range of 6.6 to 10, or In addition, it is described that barium titanate powder having a small impurity content is produced by controlling the chlorine content in the titanium compound to a predetermined concentration or less (claims 1 and 2, paragraphs 5 to 7). However, although barium titanate of Patent Document 1 is excellent in terms of purity, it cannot be expected so much in terms of an increase in specific surface area.

On the other hand, although not intended for metal titanate such as barium titanate, Patent Document 2 discloses a hydrothermal treatment of titanium oxide with potassium hydroxide as a raw material for producing barium titanate. And manufacturing a long fibrous titanium oxide having a specific surface area of 300 to 450 m ² / g by controlling the concentration and temperature of potassium hydroxide. (Claims 1, 4, 7-8, paragraphs 17-18).
That is, according to Patent Document 2, as a method for increasing the specific surface area, it is disclosed that a compound has a fiber structure.

Therefore, the prior art of fibrous barium titanate is as follows.
That is, Patent Document 3 manufactures fibrous barium titanate by a hydrothermal method (Claims 1 and 2), and Patent Document 4 also manufactures acicular barium titanate by a hydrothermal method. (Claim 1), respectively.

  Patent Document 5 discloses a dielectric composition comprising a metal titanate salt fiber having a fiber length of 1 to 1000 μm and a fiber diameter of 10 nm to 10 μm and a binder, and barium titanate is exemplified as the metal titanate. (Paragraphs 16-17, 52).

JP 2007-261912 A JP-A-2005-162585 JP-A-7-172833 JP-A-6-135720 Japanese Patent Laid-Open No. 9-2868

Although the length of the fibrous product of the said patent document 3 is 10-30 micrometers (paragraph 9, Table 1), a specific surface area is unknown. The metal titanate fiber of Patent Document 5 has a length of 1 to 1000 μm and a fiber diameter of 10 nm to 10 μm, which indicates a fine fiber structure, but the specific surface area is still unknown.
An object of the present invention is to produce barium titanate having a fiber structure and greatly increase its specific surface area.

Starting from the idea of producing barium titanate having a similar fiber structure using long-fiber titanium oxide as described in Patent Document 2 as a starting material, the present inventors The relationship between the reaction conditions such as temperature and the specific surface area of the resulting barium titanate was studied intensively.
As a result, for example, when producing barium titanate by hydrothermal synthesis of titanium oxide and barium hydroxide, the concentration of barium hydroxide together with fibrous titanium oxide is set to a predetermined low concentration of 1 mol / L or less. It was found that a fiber-like barium titanate having a very large specific surface area can be obtained by allowing the reaction to stand while being held, thereby completing the present invention.

That is, the present invention 1 is a method for producing barium titanate by reacting a titanium salt and a water-soluble barium salt in water.
The titanium salt is fibrous titanium oxide,
The concentration of the water-soluble barium salt is 0.01-1 mol / L,
By reacting in a stationary state,
A method for producing fibrous barium titanate , characterized by producing fibrous barium titanate having a crystalline shape of a fibrous shape and a specific surface area of 100 to 1000 m ² / g .

Invention 2 is a method for producing fibrous barium titanate according to Invention 1, wherein the reaction temperature is 20 to 150 ° C.

The present invention 3 is a fibrous titanium according to the present invention 1 or 2, wherein the fibrous titanium oxide is obtained by subjecting titanium oxide to an alkali treatment in water, and the water-soluble barium salt is a hydroxide of barium. It is a manufacturing method of barium acid.

By using a fibrous titanium oxide and a water-soluble barium salt as raw materials, the specific surface area that retains the fine fiber structure can be maintained by hydrothermal synthesis while keeping the concentration of the water-soluble barium salt within a specified range. A very large barium titanate can be produced, and a dielectric material having a higher capacity than the conventional one can be provided.
In general, hydrothermal treatment of titanium oxide and a water-soluble barium salt is a reaction in a relatively high temperature range. For example, in Patent Document 1, a reaction temperature of 200 to 300 ° C. is preferable (paragraph 42), and the reaction described in Patent Document 3 above. It is disclosed that the temperature is 140 to 250 ° C. (see claim 2), but in the present invention, the hydrothermal reaction is carried out in a relatively low temperature range (a suitable reaction temperature is 20 to 150 ° C .; refer to the present invention 2 ). Since they are synthesized, energy costs can be reduced and productivity can be improved. In particular, when hydrothermal synthesis is performed at around room temperature, barium titanate having a fiber structure is obtained by simply dissolving fibrous titanium oxide as a raw material and a water-soluble barium salt in water and allowing to stand for a predetermined time. Is easy to manufacture.

In the present invention, when producing barium titanate by reacting a titanium salt with a water-soluble barium salt in water, fibrous titanium oxide is used as the titanium salt, and a specific low concentration barium hydroxide salt is used under predetermined conditions. This is a method for producing a fibrous barium titanate having a specific surface area of 100 to 1000 m ² / g by reacting .

Therefore, a method for producing the fibrous barium titanate of the present invention by hydrothermally treating a titanium salt and a water-soluble barium salt will be described.
First, in this invention, the titanium salt used as a raw material needs to be fibrous titanium oxide. This fibrous titanium oxide is manufactured by subjecting at least one of titanium oxide or titanium oxide salt (titanium hydroxide) to alkaline hydrothermal treatment with potassium hydroxide and neutralizing (dealkali) washing with an inorganic acid such as hydrochloric acid or nitric acid. (Refer to the present invention 3 ).
As conditions for the alkaline hydrothermal treatment, a potassium hydroxide concentration of 10 to 25 mol / L and a temperature of 70 to 150 ° C. are preferable. Although the reaction time is 5 to 40 hours, depending on the potassium hydroxide concentration and temperature, the reaction takes place at potassium hydroxide concentration = 15-20 mol / L, temperature = 100-130 ° C., reaction time = 6-20 hours. More preferably.
The fibrous titanium oxide obtained by the hydrothermal synthesis is an ultrafine fiber crystal having a nano-order diameter and a submicron or more fiber length and a very large specific surface area as shown in FIG.
Therefore, the conditions of the fibrous titanium oxide as a raw material when producing the fibrous barium titanate of the present invention are summarized. The diameter is 1 to 100 nm, the fiber length is 100 nm to 1000 μm, and the specific surface area is 100 to 1000 m ² / g. It is preferable to use fibrous titanium oxide having a diameter of 5 to 40 nm and a specific surface area of 200 to 450 m ² / g. In addition, if fiber length is 100 nm or more, it will not specifically limit.

Subsequently, the fibrous titanium oxide and the water-soluble barium salt are hydrothermally synthesized. The water-soluble barium salt is basically a hydroxide of barium (see the present invention 3 ).
In the present invention, it is necessary to suppress the barium hydroxide concentration to 0.01 to 1 mol / L and to react in a stationary state (see the present invention 1 ). The preferred concentration of barium hydroxide is 0.1 to 0.4 mol / L.
When the concentration of barium hydroxide is less than 0.01 mol / L, the composition of the fiber approaches titanium oxide and it becomes difficult to produce barium titanate. When it exceeds 1 mol / L, the barium titanate is fibrous. There is a high risk of becoming particles.

For a barium hydroxide, a proper density range hydrate and non-hydrate are slightly different, in each hydrates such as barium hydroxide octahydrate pure product in the reaction system by dehydration of the reaction Since the concentration decreases, it is necessary to set the concentration higher than that of the non-hydrate. Conversely, the concentration of the non-hydrate may be lower than that of the hydrate.
For example, when barium hydroxide octahydrate (Ba (OH) ₂ .8H ₂ O) is added at a concentration = 1 mol / L, 0.41 for barium hydroxide non-hydrate (Ba (OH) ₂ ). About mol / L is sufficient.

In the hydrothermal synthesis, the charged molar ratio of titanium oxide and barium hydroxide is adjusted so that barium titanate maintains the fiber structure and the atomic ratio (Ba / Ti) is adjusted to 1.0 as much as possible. It is necessary to add barium more than the equimolar ratio of titanium oxide. If barium hydroxide / titanium oxide (molar ratio) is A, it is necessary to consider the solubility of barium hydroxide, but 1.0 <A < 5.0 is preferred.
When the molar ratio A is 5 or more (that is, when barium hydroxide is added excessively), the generated barium titanate is not likely to be a fiber structure but a particulate matter. Further, when the molar ratio A is 1.0 or less, there is a problem that the atomic ratio (Ba / Ti) of the generated barium titanate is lowered.
The unreacted barium hydroxide residue can be removed by neutralization washing.

As described above, the hydrothermal reaction is performed in a stationary state. This reaction in a stationary state means a reaction in which mechanical stirring is not applied from the outside.
When stirring is carried out, the fiber structure of the generated barium titanate cannot be maintained, and the specific surface area is significantly reduced.
However, agitation enough to supply barium hydroxide always uniform concentration against fibrous titanium oxide, i.e., fibrous titanium oxide and the solid content of the fibrous barium titanate is allowed to stand, barium hydroxide solution Very gentle agitation, in which only a constant concentration distribution can always be maintained, is included in the “stationary state” of the present invention.

As shown in the present invention 2 , in the hydrothermal treatment of titanium oxide and barium hydroxide, the reaction temperature is suitably 20 to 150 ° C, particularly preferably 20 to 90 ° C.
Although the reaction time is about 1 to 50 hours, depending on the concentration of barium hydroxide and the reaction temperature, the higher the temperature and the higher the concentration, the shorter the reaction time.
In general, when it reacts at a high temperature, it is easy to form particles, but a low-temperature reaction such as the above-mentioned preferable temperature range (20 to 90 ° C.) has an advantage of easily forming a fiber structure.
Therefore, preferable conditions for hydrothermal synthesis are as follows: the concentration of barium hydroxide octahydrate is 0.1 to 0.4 mol / L, the reaction temperature is 20 to 90 ° C., and the reaction time is 3 to 36 hours. .

On the other hand, the hydrothermal treatment is basically performed under atmospheric pressure and atmospheric atmosphere, but the fibrous barium titanate of the present invention can also be produced using an autoclave.
When an autoclave is used, the temperature range rises and can be produced even at about 250 ° C. Further, in order to adjust the atomic ratio (Ba / Ti) of barium titanate to 1.0, the molar ratio A is set to 1.0. It becomes possible to approach.
Even when an autoclave is used, the reaction is basically performed without stirring and standing. In addition, by making the atmospheric atmosphere an inert gas atmosphere other than carbon dioxide, the production of barium carbonate is prevented, the impurities in the barium titanate are reduced, and the atomic ratio of the barium titanate (Ba / Ti) Management can be facilitated and adverse effects on electrical characteristics when used in ceramic capacitors and the like can be reduced .

As described above, the method for producing the fibrous barium titanate of the present invention by hydrothermally treating fibrous titanium oxide and barium hydroxide (water-soluble metal salt) has been described. In place of strontium oxide, fibrous strontium titanate can be produced under the same conditions.
The metal titanate (barium titanate) of the present invention is based on a perovskite-type and spinel-type crystal structure and includes a titanium composite compound in terms of composition.
In this case, the typical crystal composition of the barium titanate of the present invention is represented by BaTiO ₃ , and the crystal composition of the titanium composite compound containing barium and strontium is represented by BaxSr ₁ -xTiO ₃ .

The fibrous barium titanate of the present invention obtained by the hydrothermal treatment is an ultrafine fiber crystal having a nano-order diameter and a fiber length of submicron or more and a very large specific surface area. FIG. 3 is an SEM enlarged image of fibrous barium titanate, which is a representative example of this metal titanate, and an ultrafine fiber structure different from the particulate form can be clearly seen.
That is, the fibrous barium titanate of the present invention is obtained by hydrothermal synthesis of fibrous titanium oxide and barium hydroxide under predetermined conditions, and the specific surface area is 100 to 1000 m ² / g , preferably 200. ˜450 m ² / g.
The length of the fiber is 100 nm to 1000 μm , preferably 1 μm to 1000 μm, and the fiber diameter is 1 to 100 nm, preferably 5 to 40 nm .
As described above, the fibrous barium titanate of the present invention obtained by hydrothermal treatment with a titanium salt in a stationary state while suppressing barium hydroxide to a predetermined low concentration is extremely excellent because it has an extremely fine fiber structure. Since a large specific surface area (100 to 1000 m ² / g) can be secured, it can be effectively used in various fields.
The application of the fibrous barium titanate of the present invention includes a dielectric material for a dielectric layer and an internal electrode in a multilayer ceramic capacitor, a dielectric material for semiconductor devices such as a varistor and a PTC (positive thermistor) material, a high frequency filter and an antenna. Examples include dielectric materials for high-frequency dielectric ceramics, dielectric catalyst materials for barrier discharge plasma, electrostatic / antistatic agents, paints having a photocatalytic function, paints for deodorization / deodorization, battery materials (negative electrode materials), and the like.

Hereinafter, Production Examples of titanium oxide fibers, examples of producing the barium titanate fibrous invention using this fibrous titanium oxide, property confirmation fibrous barium titanate obtained in Example, Various test examples such as identification of composition and measurement of specific surface area will be sequentially described.
The present invention is not limited to the following production examples, examples, and test examples, and it is needless to say that arbitrary modifications can be made within the scope of the technical idea of the present invention.

< Production example of fibrous titanium oxide>
After putting 10g of titanium oxide powder (Nippon Aerosil Co., Ltd., P25) in 100mL of 17M potassium hydroxide (Kanto Chemical Co., Ltd., deer special grade) aqueous solution and stirring well, let it stand at 110 ° C incubator for 20 hours Synthesized. The thermostat used a Teflon container.
Then, after 20 hours, the container was taken out and the solid content was separated with a centrifuge, and the excess alkali residue in the solid content was neutralized with 10% hydrochloric acid.
Then, the desalting washing | cleaning process of solid content was performed 3 times using the pure water with the centrifuge, and the dispersion | distribution slurry of the fibrous titanium oxide was obtained.

Therefore, the fibrous titanium oxide and barium hydroxide obtained in the above production example were hydrothermally treated under predetermined conditions to produce fibrous barium titanate.
The distinction between the following production examples and production comparison examples is based on the production method of the present invention 4.
<< Production Example of Fibrous Barium Titanate >>
Among the following Production Examples 1 to 5, Production Example 1 is an example in which the concentration of barium hydroxide octahydrate is 0.4 mol / L and the reaction is allowed to stand at a temperature of 80 ° C. Production Example 2 is an example in which the reaction temperature was increased from 80 ° C. in Example 1 to 150 ° C. Production Example 3 is an example in which the reaction temperature was lowered to 25 ° C. (normal temperature). Production Example 4 is an example in which the concentration of barium hydroxide octahydrate was increased to 1.0 mol / L. Production Example 5 is an example in which the concentration of the hydrate was lowered to 0.1 mol / L.
On the other hand, in the manufacturing Comparative Examples 1 to 3, Comparative Production Example 1 as the basis of the above Preparation Example 1, an example was reacted under stirring. Production Comparative Example 2 is an example in which the concentration of barium hydroxide octahydrate was adjusted to be higher than the appropriate range of the present invention and allowed to stand for reaction. Production Comparative Example 3 is an example in which the concentration of the hydrate was adjusted to be higher than the appropriate range of the present invention and the reaction was performed in a stirred state.
The left column and center column of FIG. 1 summarize reaction conditions such as the temperature during hydrothermal treatment, the concentration of barium hydroxide octahydrate, and the molar ratio of barium hydroxide to titanium oxide during hydrothermal treatment.

(1) Production Example 1
Barium hydroxide octahydrate (manufactured by Kanto Chemical Co., Ltd., special grade ACS) is dissolved in 500 mL of pure water heated to 80 ° C. to adjust the concentration to 0.4 mol / L, and the fibrous oxidation of the above production example is performed. 10 g (in terms of solid content) of titanium slurry was added, and hydrothermal synthesis was performed at 80 ° C. for 12 hours. In this case, the charged molar ratio of barium hydroxide and titanium oxide was Ba (OH) ₂ / TiO ₂ = 1.5.
Then, after 12 hours, the solid content was separated with a centrifuge, and the excess alkali residue in the solid content was neutralized to pH 7 with 10% hydrochloric acid (manufactured by Kanto Chemical Co., Inc., for measuring harmful metals).
Subsequently, desalting and washing treatment of solid content was performed 3 times using pure water in a centrifuge, and a dispersion slurry of barium titanate was obtained.

(2) Production Example 2
Based on Production Example 1, a reaction slurry was treated under the same conditions as Production Example 1 except that the reaction temperature was 150 ° C. to obtain a dispersion slurry of barium titanate.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 1.5.

(3) Example 3
Based on Production Example 1, a dispersion slurry of barium titanate was obtained by treating under the same conditions as in Production Example 1 except that a hydrothermal reaction was performed at a reaction temperature of 25 ° C. for 36 hours.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 4.0.

(4) Production Example 4
Based on Production Example 1, except that the concentration of barium hydroxide octahydrate was adjusted to 1.0 mol / L, the dispersion slurry of barium titanate was treated under the same conditions as in Production Example 1. Obtained.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 1.5.

(5) Production Example 5
Based on Production Example 1, except that the concentration of barium hydroxide octahydrate was adjusted to 0.1 mol / L, the dispersion slurry of barium titanate was treated under the same conditions as in Production Example 1. Obtained.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 1.5.

(6) Manufacturing Comparative Example 1
Based on Production Example 1, except that the hydrothermal reaction was performed under a stirring condition of 100 rpm, a dispersion slurry of barium titanate was obtained under the same conditions as in Production Example 1.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 1.5.

(7) Production Comparative Example 2
Based on Production Example 1, except that the concentration of barium hydroxide octahydrate was adjusted to 10 mol / L, a dispersion slurry of barium titanate was obtained under the same conditions as in Production Example 1. .
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 40.

(8) Production Comparative Example 3
Under the same conditions as in Production Example 1, except that the concentration of barium hydroxide octahydrate was adjusted to 10 mol / L on the basis of Production Example 1 and subjected to a hydrothermal reaction for 3 hours with stirring at 500 rpm. The dispersion slurry of barium titanate was obtained by processing.
The molar ratio of barium hydroxide to titanium oxide was Ba (OH) ₂ / TiO ₂ = 40.

Subsequently, in order to carry out the property analysis and composition analysis of each barium titanate obtained in the above Production Examples 1 to 5 and Production Comparative Examples 1 to 3, the dispersion slurry of each barium titanate was 50 ° C. using a quartz boat. And dried to obtain a solid.
<Test example of barium titanate>
Then, about each solid substance of the said barium titanate obtained by manufacture Examples 1-5 and manufacture comparative examples 1-3, first, it microscopically observed centering on the presence or absence of the fiber structure with the scanning electron microscope (SEM). .
In addition, the solid-state composition analysis is performed by an energy dispersive X-ray fluorescence spectrometer (SEM-EDX) attached to the scanning electron microscope, and the specific surface area is measured by a water vapor adsorption amount measuring apparatus (moisture adsorption BET). did. The specific surface area and Ba / Ti ratio of the obtained barium titanate are summarized in the right column of FIG.
[Model name of measuring device]
Field emission scanning electron microscope (FE-SEM): Hitachi, S-4800
Energy dispersive X-ray fluorescence spectrometer (EDX): manufactured by HORIBA, Ltd., trade name EMAX EX250 7593-H
Water vapor adsorption measuring device: QUANTACHROME, trade name Hydrosorb1000

(1) Production Example 1
As shown to FIG. 3A-B, it was confirmed that the obtained solid substance is an aggregate | assembly which has a fibrous structure.
Moreover, as shown in FIG. 4, it was identified from the EDX pattern of the fluorescent X-ray analyzer that the solid matter was barium titanate having a fiber structure with a Ba / Ti ratio = 0.371.
The specific surface area of the fibrous barium titanate was 351 m ² / g.

(2) Production Example 2
It was confirmed that the obtained solid was fibrous barium titanate having a Ba / Ti ratio = 0.413 and a specific surface area = 323 m ² / g.

(3) Production Example 3
It was confirmed that the obtained solid was fibrous barium titanate having a Ba / Ti ratio = 0.327 and a specific surface area = 375 m ² / g.

(4) Production Example 4
It was confirmed that the obtained solid was fibrous barium titanate having a Ba / Ti ratio = 0.409 and a specific surface area = 338 m ² / g.

(5) Production Example 5
It was confirmed that the obtained solid was fibrous barium titanate having a Ba / Ti ratio = 0.298 and a specific surface area = 366 m ² / g.

(6) Manufacturing Comparative Example 1
It was confirmed that the obtained solid was a mixed aggregate having two types of structures, particulate and fibrous . Further, the Ba / Ti ratio was 0.785, which was a ratio close to 1.0, but the specific surface area was as low as 128 m ² / g.

(7) Production Comparative Example 2
As shown in the SEM image of FIG. 5, it was confirmed that the obtained solid was in the form of particles and was particulate barium titanate having a Ba / Ti ratio of 1.009 and a specific surface area of 35.6 m ² / g. It was.

(8) Production Comparative Example 3
It was confirmed that the obtained solid was particulate barium titanate having a Ba / Ti ratio = 1.006, a specific surface area = 103 m ² / g, and a particle size = 20 to 30 nm.

In the fibrous barium titanate obtained in the above Production Examples 1 to 5, the Ba / Ti ratio is 0.298 to 0.413 and is 1.0 or less. This is barium hydroxide in hydrothermal synthesis. Since the concentration is very low, it can be estimated that the reaction efficiency to titanic acid having a high Ba introduction energy is lowered.
Incidentally, the Ba / Ti ratio approaches 1.0 as much as possible when hydrothermal synthesis is performed with high-concentration barium hydroxide, but there is a problem that the fiber structure is easily broken when Ba is introduced. Therefore, in the present invention, the barium titanate having a fiber structure can be efficiently produced by static synthesis while adjusting the concentration of barium hydroxide low.

<< Test Evaluation of Production Examples and Production Comparative Examples >>
Although the concentration of barium hydroxide is suppressed to a low level within the proper range of the present invention, it was a mixture of particles and fibers in Production Comparative Example 1 in which the hydrothermal reaction was carried out in a stirred state, but the resulting barium titanate was obtained. It was found that the specific surface area of was extremely small compared to Production Examples 1-5. Thereby, in order to obtain the barium titanate of a fiber structure, it has confirmed that it was important to make a hydrothermal reaction in a stationary state. In addition, although the stirring speed of manufacture comparative example 1 is 100 rpm, when this stirring speed is raised, the ratio of a particle structure will increase and it can estimate that a specific surface area further reduces.
Although it is a hydrothermal reaction in a stationary state, in Production Comparative Example 2 in which the concentration of barium hydroxide greatly exceeds the appropriate range of the present invention, barium titanate becomes particulate and a fiber structure cannot be obtained. The specific surface area of barium titanate was very small. Thereby, the production of barium titanate having a fiber structure was greatly affected by the concentration of barium hydroxide, and it was confirmed that it was important to suppress the concentration to a predetermined level or lower.
In Production Comparative Example 3 in which the hydrothermal reaction was performed with stirring at a barium hydroxide concentration exceeding the proper range of the present invention, barium titanate naturally became particles, so the specific surface area was also that of the example. It was far from that.

In contrast, in Production Examples 1 to 5, the obtained barium titanate clearly had a fiber structure, as shown in the SEM images of FIGS. This fiber structure is also supported by the fact that the specific surface areas of Production Examples 1 to 5 are greatly increased compared to the barium titanate particles of Comparative Examples 2 to 3.
Therefore, when the production examples 1 to 5 are compared with the production comparison examples 1 to 3, in order to efficiently produce the barium titanate having a fiber structure, the concentration of barium hydroxide is suppressed to an appropriate range below a predetermined value, And it became clear that it was necessary to make it hydrothermally react in a stationary state.
Even if the barium hydroxide concentration condition and the standing condition in the present invention are satisfied, in the hydrothermal treatment using particulate titanium oxide (that is, general commercially available titanium oxide) instead of fibrous , It goes without saying that only barium titanate can be obtained.

Summary of temperature during hydrothermal reaction, concentration of barium hydroxide octahydrate, molar ratio of charged barium hydroxide and titanium oxide in hydrothermal reaction, specific surface area and Ba / Ti ratio of the obtained barium titanate It is a chart. It is a photograph which shows the SEM image (100,000 times) of the fibrous titanium oxide which is a raw material. FIG. 3A is a photograph showing an SEM image of fibrous barium titanate obtained in Production Example 1, FIG. 3A is a photograph at a magnification of 100,000 times, and FIG. 3B is a photograph at a magnification of 100,000 times. 1 is an EDX peak pattern diagram of fibrous barium titanate obtained in Production Example 1. FIG. It is a photograph which shows the SEM image (100,000 times) of the barium titanate obtained in manufacture comparative example 2.

Claims (3)

In a method for producing barium titanate by reacting a titanium salt and a water-soluble barium salt in water,
The titanium salt is fibrous titanium oxide,
The concentration of the water-soluble barium salt is 0.01-1 mol / L,
By reacting in a stationary state,
A method for producing fibrous barium titanate , characterized by producing fibrous barium titanate having a crystal shape of a fiber and a specific surface area of 100 to 1000 m ² / g . The temperature of reaction is 20-150 degreeC, The manufacturing method of the fibrous barium titanate of Claim 1 characterized by the above-mentioned. The method for producing fibrous barium titanate according to claim 1 or 2 , wherein the fibrous titanium oxide is obtained by alkaline treatment of titanium oxide in water, and the water-soluble barium salt is a hydroxide of barium. .

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