KR101295161B1 - Method for manufacturing composite oxide powder - Google Patents

Abstract

Provides a method for efficiently and economically producing a fine, large surface area, high crystalline perovskite-type composite oxide which can be suitably used for dielectric layers of multilayer ceramic capacitors having a large number of dielectric layers and thin layers. do.
Perovskite complex oxide by reacting a titanium oxide slurry having a titanium oxide powder having an integrated width of the diffraction peak on the (101) plane measured by X-ray diffraction of 2.0 ° or less in water with an alkali earth element hydroxide added thereto. Creates.
Titanium oxide powder having a specific surface area of 100 to 450 m ² / g is used.
As the hydroxide of the alkaline earth element, a hydroxide containing no hydrated water is used.
In addition, using a barium hydroxide as the hydroxide of the alkaline earth element, the perovskite-type composite oxide obtains BaTiO ₃ powder.

Description

Manufacturing method of complex oxide powder {METHOD FOR MANUFACTURING COMPOSITE OXIDE POWDER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite oxide, and more particularly, to a method for producing a composite oxide that can be suitably used as a ceramic raw material for ceramic electronic components.

As a manufacturing method of the composite oxide powder which can manufacture complex oxides, such as a fine grain and excellent crystallinity, such as barium titanate economically, the method as demonstrated below is proposed.

For example, the general formula ABO ₃ pages represented by the perovskite (perovskite) element to a method for manufacturing a composite oxide powder having a structure, constituting one A-site element containing crystal water (結晶水) hydroxide and, 250m ^It has a mixing process step of mixing titanium oxide powder having a specific surface area of ² / g or more, the mixing process step is a heat treatment process to produce a dissolved solution of the A-site component dissolved only in the water of the crystal water and And a method for producing a composite oxide powder including a reaction step in which a titanium oxide powder and a solution react with each other to generate a reaction compound, and allowing the solution generation step and the reaction step to proceed continuously (see Patent Document 1). .

In addition, Patent Document 1 discloses calcination of the obtained composite oxide.

And according to the method of this invention of patent document 1, a complex oxide with few abnormalities, a desired ultrafine grain, and excellent crystallinity is obtained, and a calcination process is carried out, and a cubic system complex oxide is carried out. It is supposed that a tetragonal composite oxide having excellent crystallinity can be produced by transition of a crystal system.

By the way, the multilayer ceramic used as a dielectric ceramic sintered compact layer in the capacitor (for example, BaTiO ₃ based ceramic layer), the particle size of the ceramic particles haejimyeon fine constituting, there is known that the dielectric constant is lowered, lowering of the dielectric constant, the ceramic It is caused by the fall of the crystallinity (the ratio of c-axis to the a-axis (c / a-axis ratio) of a crystal axis) of a sintered compact.

In order to solve this problem of lowering the dielectric constant, the particle size of the powder at the stage of the raw material powder before sintering (for example, calcined powder of barium titanate material) before the ceramic sintered body layer as the dielectric layer is small. It is necessary to be a raw material powder with high crystallinity.

From this point of view, in Patent Document 1, the synthesized fine barium titanate powder is calcined at 900 to 1000 ° C, whereby a fine barium titanate powder having a c / a-axis ratio of 1.0075 to 1.0088 and a specific surface area of 7.31 to 3.88 m ² / g is obtained. To lose.

However, when the element thickness (thickness of the dielectric layer interposed between internal electrodes) of the multilayer ceramic capacitor is less than 1 µm, the barium titanate powder obtained by the method of Patent Document 1 is not sufficient.

As another method for producing a composite oxide, in an atmosphere where carbon dioxide is not present, the titanium oxide particles and the water-soluble barium compound are added in equimolar amounts to the number of moles of the titanium oxide particles, and the pH is 11.5 or more and 13.0. In the following aqueous solution, the manufacturing method of the barium titanate powder which has a reaction process made to react at the temperature of 100 degrees C or less is proposed (claim 2 of patent document 2).

According to the method of this invention of patent document 2, barium titanate powder with a narrow particle size distribution can be manufactured inexpensively, preventing the chlorine impurity mixing.

However, in the method of the invention of patent document 2, although the barium titanate powder whose particle diameter is 0.085-0.15 micrometers is synthesize | combined from the titanium oxide of 40 m <^2> / g, it is hard to think that the crystallinity of the obtained barium titanate is high enough, In addition, since calcination is not performed, it is estimated that crystallinity is low (paragraph 0025).

Also, for the method of Patent Document 2, need to be synthesized in the atmosphere unless the CO ₂ is present, this is a problem is caused in the pharmaceutical manufacturing process.

In addition, in all of the patent documents 1 and 2, the range of the powder characteristic required for a TiO ₂ material is not clear, and by any method of patent documents 1 and 2, the powder of which is required for a multilayer ceramic capacitor with high characteristics is required. It is a fact that it is difficult to obtain a raw material powder with a small particle diameter and high crystallinity.

Japanese Patent No. 4200427 Japanese Patent No. 4057475

MEANS TO SOLVE THE PROBLEM This invention solves the said subject, and it is a fine, large surface area, and high crystallinity which can be used suitably for the use of the dielectric material of many laminated layers, and the constituent material of the dielectric layer of a laminated multilayer ceramic capacitor. It is an object of the present invention to provide a method for producing a perovskite complex oxide, which can efficiently and economically produce a lobe-sky complex oxide.

In order to solve the above problems, the method for producing a perovskite complex oxide of the present invention,

As a method for producing a perovskite complex oxide represented by general formula ABO ₃ ,

A slurry preparation step of preparing a titanium oxide slurry obtained by dispersing a titanium oxide powder having a integral width of a diffraction peak of the (101) plane measured by X-ray diffraction at 2.0 ° or less in water;

It is characterized by including the reaction process which produces | generates a perovskite type complex oxide by adding and reacting the hydroxide of an alkaline-earth element to the said titanium oxide slurry.

In the manufacturing method of the perovskite type composite oxide of this invention, it is preferable that the specific surface area of the said titanium oxide powder is 100-450 m <^2> / g.

It is also preferable to use a hydroxide which does not contain hydrated water as the hydroxide of the alkaline earth element.

It is also preferable that the hydroxide of the alkaline earth element is barium hydroxide, and the perovskite-type composite oxide is BaTiO ₃ .

Moreover, while A site is Ba, the one part is substituted by Sr and / or Ca, It is characterized by the above-mentioned.

In addition, it is preferable to further include a step of heat-treating the perovskite-type composite oxide produced in the reaction step.

In the method for producing a perovskite-type composite oxide represented by the general formula ABO ₃ of the present invention, a titanium oxide powder having an integral width of the diffraction peak of the (101) plane measured by X-ray diffraction of 2.0 ° or less is dispersed in water. A slurry preparation step of preparing a titanium oxide slurry and a reaction step of producing a perovskite-type composite oxide by adding an alkali earth element hydroxide to the titanium oxide slurry and reacting the same, are used in the conventional solid-liquid reaction. The perovskite complex oxide with a specific surface area larger than the perovskite complex oxide obtained by this can be obtained.

That is, when the titanium oxide powder whose integral width of the diffraction peak of the (101) plane measured by X-ray diffraction is 2.0 degrees or less is used, the larger specific surface area is compared with the case where titanium oxide whose integral width is larger than 2.0 degrees is used. It becomes possible to manufacture the perovskite-type composite oxide having a compound without particularly requiring a complicated production process.

In addition, in the production method of the perovskite-type composite oxide of the present invention, by a specific surface area of using titanium oxide powder of 100 ~ 450m ² / g, a specific surface area of a 50m ² / g or more pages lobe effectively Perovskite - Type compound oxide It becomes possible to manufacture.

In addition, by using a hydroxide containing no hydrated water as the hydroxide of the alkaline earth element, it is possible to add the solid oxide directly to the slurry in which the titanium oxide powder or the like is dispersed, thereby simplifying the manufacturing process. In addition, by using a hydroxide of an alkaline earth element that does not contain hydrated water, a temperature rise occurs due to the heat of dissolution at the time of addition to the slurry, so that the synthesis reaction is promoted.

In addition, when the hydroxide of the alkaline earth element is barium hydroxide, BaTiO ₃ powder, which is a perovskite complex oxide, can be efficiently produced. In addition, by directly adding barium hydroxide containing no hydrated water to the titanium oxide slurry, the temperature of the slurry rapidly rises to around 100 ° C. due to the heat of dissolution, thereby promoting the synthesis reaction to form a BaTiO ₃ powder which is a perovskite complex oxide. It can manufacture more efficiently.

Moreover, according to this invention, it is also possible to manufacture the perovskite type composite oxide of the composition which substituted a part of Ba which comprises A site with Sr and / or Ca, In that case, a characteristic is adjusted and a desired The perovskite-type composite oxide having the characteristic of being can be efficiently produced.

The raw material of Sr and / or Ca substituted with Ba may be included in the titanium oxide slurry, or may be added to the titanium oxide slurry prior to or simultaneously with the hydroxide of the alkaline earth element immediately before the reaction step.

Further, in the present invention, the perovskite-type composite oxide produced in the reaction step is heat-treated, whereby the c / a-axis ratio can be increased to obtain a perovskite-type composite oxide having high crystallinity.

For example, a tetragonal perovskite-type composite oxide having a large c / a axis ratio (greater than 1) is obtained by heat treatment at a temperature of 800 to 1000 ° C. In the present invention, since the titanium oxide powder having an integral width of 2.0 ° or less is used, it is possible to suppress grain growth in the heat treatment step than when titanium oxide having an integral width of 2.0 ° or more is used. It is possible to obtain a perovskite complex oxide having a high crystallinity with a large specific surface area and a large c / a axis ratio.

Fig. 1 shows the integral width of diffraction peaks of the (101) plane measured by X-ray diffraction of a TiO ₂ used as a Ti raw material in one embodiment of the present invention (barium titanate powder obtained by the reaction). It is a figure which shows the relationship of the specific surface area of a.
It is a figure which shows the relationship between the specific surface area of the barium titanate powder after calcining obtained in Example 1 of this invention, and the c / a-axis ratio of a crystal | crystallization.

Examples of the present invention are shown below to describe the features of the present invention in more detail.

Example 1

Anatase-type titanium oxide (TiO ₂ ) powders No. 1 to No. 9 having specific surface areas as shown in Table 1 were prepared.

Then, the integral width of the (101) plane of each TiO ₂ powder was determined by X-ray diffraction (CuKα as the source). The integral width was determined by measuring the (101) plane peak of each TiO ₂ powder by using an X-ray diffraction apparatus and dividing the area (integration intensity) of the peak by the peak intensity. In Table 1, No. 8 and 9 with * are comparative TiO ₂ which does not satisfy the requirements of the present invention.

Then, TiO ₂ powders No. 1 to No. 9 in Table 1 were mixed with pure water, and nine types of titanium oxide slurries having a content of titanium oxide (TiO ₂ ) of 23% by weight were produced.

However, in the present invention, the titanium oxide concentration in the titanium oxide slurry is usually 10% by weight or more.

Then, each produced titanium oxide slurry was heated to 70 ° C, and then barium hydroxide was added so as to have a predetermined Ba / Ti ratio while stirring the titanium oxide slurry. In this example, barium hydroxide (Ba (OH) ₂ ) containing no hydrated water as barium hydroxide was added in a solid state. By adding in solid state, the temperature of the slurry rises to near 100 degreeC by heat of dissolution, and reaction can be started quickly.

Moreover, the temperature of the titanium oxide slurry at the time of adding barium hydroxide may just be 40 degreeC or more.

It is also possible to add barium hydroxide as an aqueous solution. In that case, a required reaction can be performed by heating and raising a temperature.

However, as mentioned above, since the heat of dissolution can be effectively used for raising the temperature of the TiO ₂ slurry, it is preferable that barium hydroxide is added in a solid state without containing hydrated water.

The barium titanate (BaTiO ₃ ) slurry was obtained by adding barium hydroxide as mentioned above, and keeping titanium oxide and barium hydroxide reacting for 1 h at the temperature of 80 degreeC or more, stirring. Then, the obtained slurry was dried to obtain a barium titanate (BaTiO ₃ ) powder.

Table 1 and FIG. 1 show the relationship between the value of the integration width obtained as described above for the TiO ₂ used as the Ti raw material and the specific surface area of the obtained barium titanate powder.

Table 1 and FIG. 1 show that barium titanate powder having a large specific surface area is obtained by using TiO ₂ having an integrated width of 2.0 ° or less.

For example, when comparing the case of using titanium oxide (integral width 1.58 °) of the No.2 and No.8 of titanium oxide (integral width 2.20 °), both the both the specific surface area of the TiO ₂ material is almost 400m ² / The equivalent surface area of the synthesized BaTiO ₃ powder is equivalent to g, and the titanium oxide of No. 8 (integrated width 2.20 °) is 58 m ² / g when using No. 2 titanium oxide (integral width 1.58 °). In the case of using), it is understood that barium titanate powder having a large specific surface area is obtained when 33 m ² / g and titanium oxide of No. 2 having an integrated width of 2.0 ° or less are used.

In addition, when TiO ₂ whose integral width of the diffraction peak on the (101) plane measured by X-ray diffraction was used was higher than 2.0 °, barium titanate powder having a large specific surface area was not obtained. Since TiO ₂ having low properties is easy to dissolve in alkali and dissolution-reprecipitation reaction of TiO ₂ easily occurs, grain growth or bonding of neighboring particles occurs, and the barium titanate powder obtained by reaction with barium hydroxide is also a particle. Is large and the specific surface area decreases.

In addition, these powders were calcined by using different heat conditions in the range of 800 to 1000 ° C.

Table 2 and FIG. 2 show the relationship between the specific surface area of the barium titanate powder after calcining and the c / a axis ratio of the crystal.

From Table 2 and FIG. 2, it can be seen that, after the synthesis by the solid-liquid reaction, the barium titanate powder having a large specific surface area before calcination, the greater the c / a-axis ratio after calcination, and the higher perovskite-type composite oxide can be obtained. .

According to the method of this invention, it was confirmed from the said Example that a perovskite type | mold composite oxide with a fine grain, a large specific surface area, and high crystallinity is obtained.

In this way, when the integral width of 2.0 ° or less with the TiO _2, is the specific surface area is large barium titanate powder obtained in accordance with the following reasons. That is, since TiO ₂ having high crystallinity, whose integral width of the diffraction peak of the (101) plane measured by X-ray diffraction is 2.0 ° or less, is difficult to dissolve in alkali, and the dissolution-reprecipitation reaction of TiO _{2 also} hardly occurs, Since it is difficult to generate grain growth or bonding between neighboring particles, the barium titanate powder obtained by the reaction with barium hydroxide has small particles, and the specific surface area increases. As a result, it is possible to obtain barium titanate powder which is fine even after calcination and has a large specific surface area, a large c / a-axis ratio, and high crystallinity.

[Example 2]

The final composition of (Ba Ca _{0 .95 0 .05)} TiO ₃ No.5 of the titanium oxide in Table 1, so that the (TiO ₂₎ powder, calcium carbonate (CaCO ₃₎ powder, barium hydroxide (Ba (OH) ₂ ) a powder was prepared.

Then, a titanium oxide powder (titanium oxide powder of No. 5 in Table 1), calcium carbonate (CaCO ₃ ) powder and pure water were mixed, and a slurry having a total content of TiO ₂ and CaCO ₃ in a content of 23% by weight. Produced.

The titanium oxide slurry containing this Ca component was heated and heated up to 70 degreeC, and barium hydroxide was added so that it might become a predetermined Ba / Ti ratio while stirring.

Here too, barium hydroxide (Ba (OH) ₂ ) containing no hydrated water as barium hydroxide was added in a solid state.

Then, the reaction performed by maintaining a temperature of 80 ℃ or 1h with stirring (Ba, Ca) TiO ₃ to obtain a slurry.

Then, the obtained slurry was dried to obtain barium titanate powder ((Ba, Ca) TiO ₃ powder) in which a part of Ba was substituted with Ca.

According to the method of Example 2, it was confirmed that the specific surface area is obtained by a large general formula perovskite-type composite oxide powder represented by _{(Ba 0 .95 Ca 0 .05)} TiO 3. In addition, the specific surface area of the perovskite-type composite oxide powder ((Ba Ca _{0 .95 0 .05)} TiO ₃ powder) obtained by the reaction was about 60m ² / g.

This addition (Ba Ca _{0 .95 0 .05)} TiO ₃ calcined powder by using a heat treatment furnace to varying temperature conditions in the range of 800 ~ 1000 ℃.

As a result, when the specific surface area is calcined under the conditions of about 14 m ² / g (for example, at 820 ° C. and 2 h), the perovskite-type composite oxide having a high crystallinity of about 1.007 powder ((Ba Ca _{0 .95 0 .05)} TiO ₃ powder) was confirmed to be obtained.

In addition, in Example 2, calcium carbonate (CaCO ₃ ) powder was used as the Ca source, but the Ca source is not limited to the CaCO ₃ powder. For example, various salts such as calcium acetate, calcium nitrate, and calcium hydroxide may also be used. It is possible.

[Example 3]

The final composition of (Ba _{0 .95 0 .05} Sr) TiO ₃ No.5 of the titanium oxide in Table 1, so that the (TiO ₂₎ powder, strontium nitrate (Sr (NO _{3) 2)} powder, Ba (OH ) ₂ powder was prepared.

Then, titanium oxide powder (titanium oxide powder of No. 5 in Table 1), strontium nitrate (Sr (NO ₃ ) ₂ ) powder, and pure water were mixed to obtain a total amount of TiO ₂ and Sr (NO ₃ ) ₂ . A slurry having a content of 23 wt% was produced.

The titanium oxide slurry containing this Sr component was heated up to 70 degreeC, and barium hydroxide was added so that predetermined | prescribed Ba / Ti ratio might be carried out while stirring.

Here too, barium hydroxide (Ba (OH) ₂ ) containing no hydrated water as barium hydroxide was added in a solid state.

After the addition of barium hydroxide, the (Ba, Sr) TiO ₃ slurry was obtained by maintaining the reaction at a temperature of 80 ° C. or higher for 1 h while stirring.

Then, the obtained slurry was dried to obtain barium titanate powder ((Ba, Sr) TiO ₃ powder) in which a part of Ba was substituted by Sr.

According to the method of Example 3, it was confirmed that the specific surface area is obtained by a large general formula perovskite-type composite oxide powder represented by (Ba _{0 .95 0 .05} Sr) TiO _3. In addition, the specific surface area of the perovskite-type composite oxide powder ((Ba _{0 .95 0 .05} Sr) TiO ₃ powder) obtained by the reaction was about 60m ² / g.

This addition (Ba _{0 .95 0 .05} Sr) TiO ₃ calcined powder by using a heat treatment furnace to varying temperature conditions in the range of 800 ~ 1000 ℃.

As a result, when the specific surface area is calcined under the conditions of about 14 m ² / g (for example, at 830 ° C. and 2 h), a highly crystalline perovskite complex oxide having a c / a axis ratio of about 1.007. powder ((Ba _{0 .95 0 .05} Sr) TiO ₃ powder) was confirmed to be obtained.

In Example 3, strontium nitrate (Sr (NO ₃ ) ₂ ) powder was used as the Sr source, but the Sr source is not limited to (Sr (NO ₃ ) ₂ ) powder, for example, strontium hydroxide or strontium carbonate. It is also possible to use such.

The present invention is not limited to the above examples, but the solid content concentration of the titanium oxide slurry in which the titanium oxide powder is dispersed in water, the reaction temperature and the reaction time when the alkaline earth element hydroxide is added to the titanium oxide slurry Condition, range of specific surface area of titanium oxide powder as raw material, type of alkaline earth element, substitution ratio when substituting part of A site with Sr and / or Ca, perovskite complex oxide produced in reaction process With respect to conditions and the like, various applications and modifications can be made within the scope of the invention.

Claims (6)

As a method for producing a perovskite complex oxide represented by general formula ABO ₃ ,
A slurry preparation step of preparing a titanium oxide slurry obtained by dispersing a titanium oxide powder having an integral width of a diffraction peak of the (101) plane measured by X-ray diffraction at 2.0 ° or less in water;
A reaction step of producing perovskite-type composite oxide by adding and reacting a hydroxide of an alkaline earth element to the titanium oxide slurry,
Method for producing a perovskite-type composite oxide, characterized in that it comprises a step of heat-treating the perovskite-type composite oxide produced in the reaction step. The method of claim 1,
A method for producing a perovskite-type composite oxide, characterized in that the specific surface area of the titanium oxide powder is 100 ~ 450m ² / g. The method according to claim 1 or 2,
A method for producing a perovskite complex oxide, characterized in that a hydroxide containing no hydrated water is used as the hydroxide of the alkaline earth element. The method according to claim 1 or 2,
The hydroxide of the alkaline earth element is barium hydroxide, and the perovskite complex oxide is BaTiO ₃ , wherein the perovskite complex oxide is produced. The method of claim 3,
A site is Ba, a part of which is substituted by Sr and / or Ca, wherein the perovskite complex oxide is produced. delete

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