KR20120079809A - Method for manufacturing perovskite-typed composite oxide powder - Google Patents

Abstract

PURPOSE: A manufacturing method of perovskite-type composite oxide powder is provide to improve crystalline and surface area by using titanium dioxide powder having pore volume a fixed specific surface area. CONSTITUTION: A manufacturing method of titanate barium based perovskite-type composite oxide powder which is represented by a general formula of ABO3 comprises the following step: reacting BaOH with a solution including titanium dioxide powder. The titanium dioxide powder has a specific surface area of 250m^2/g or greater and a pore volume of 0.38mL/g or greater. A part of the Ba which consists the A site is substituted with Sr and/or Ca. The manufacturing method of the perovskite-type complex oxide additionally includes the following step of heat treating the perovskite-type complex oxide which is created in the reaction process.

Description

Manufacturing method of perovskite type composite oxide powder {METHOD FOR MANUFACTURING PEROVSKITE-TYPED COMPOSITE OXIDE POWDER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a perovskite-type composite oxide represented by general formula ABO _3, and in particular, a barium titanate-based perovskite-type composite oxide that can be suitably used as a ceramic raw material for ceramic electronic components. It relates to a manufacturing method of.

As a method for economically producing a perovskite-type composite oxide such as barium titanate having fine crystallinity and excellent crystallinity, for example, a method of a perovskite-type composite oxide using a solid-liquid reaction as described below. This is proposed (refer patent document 1).

This method comprises a mixing treatment step of mixing a hydroxide containing crystallized water of the elements constituting the A-site component with a titanium oxide powder having a specific surface area of 250 m ² / g or more. A dissolution solution generation step of producing a dissolved solution of the A-site component with only the water of the crystal water by heat treatment; and a reaction step of reacting the titanium oxide powder with the solution to generate a reaction compound, while producing a dissolved solution. It is a manufacturing method of the complex oxide powder which made process and reaction process progress continuously.

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

And according to the method of this invention of patent document 1, the composite oxide which has few abnormalities and is very fine and excellent in crystallinity is obtained, and by calcining this, a crystal system transfers from a cubic crystal oxide, and crystallinity is carried out. It is said that this excellent tetragonal composite oxide can be manufactured.

By the way, in order to obtain particulate barium titanate (BaTiO ₃ ) -based perovskite-type composite oxide powder by solid-liquid reaction as in the prior art, barium hydroxide (Ba (OH) ₂ ) is oxidized in view of sufficiently advancing the reaction. it is necessary to reduce the distance which diffusion within the titanium (TiO _2). Therefore, in the method of Patent Document 1, titanium oxide powder having a specific surface area (SSA) of 250 m ² / g or more (that is, titanium oxide powder having a specific surface area equivalent diameter or less) is used as the titanium oxide powder as a raw material. have.

However, when the fine titanium oxide primary particles as described above are strongly aggregated, it is difficult to disperse the fine aggregates to the individual primary particles under normal agitation, and they exist as aggregated particles in the liquid.

Therefore, in order to sufficiently react titanium oxide (TiO ₂ ) and barium hydroxide (Ba (OH) ₂ ), it is necessary to diffuse barium hydroxide even inside the titanium oxide agglomerate, but a dense agglomerate of titanium oxide powder exists. In this case, it is difficult to diffuse the barium hydroxide even inside the titanium oxide aggregate, resulting in insufficient reaction between the titanium oxide powder raw material and the barium hydroxide.

In recent years, multilayer ceramic capacitors have been put into practical use in areas where the thickness (element thickness) of the ceramic layer as the dielectric layer interposed between the internal electrodes for capacitance formation is less than 1 µm. There is an increasing demand for this high barium titanate powder, but it is a fact that the above-described technique of Patent Document 1 cannot necessarily meet the above requirements.

Japanese Patent No. 4200427

MEANS TO SOLVE THE PROBLEM This invention solves the said subject, For example, there are many dielectric layers laminated | stacked, and it is fine, surface area, and crystallinity which can be used suitably as a constituent material of dielectric layers in a multilayer ceramic capacitor thinned, etc. An object of the present invention is to provide a method for efficiently producing a high barium titanate-based perovskite complex oxide.

In order to solve the above problems, the inventors concerning the for producing a perovskite-type composite oxide powder of barium titanate (BaTiO ₃₎ based on the particulate by the solid-liquid reaction, subjected to a variety of reviews, conventionally, the raw material ratio of the titanium oxide powder It is thought that the reactivity can be secured by selecting the TiO ₂ powder having an appropriate specific surface area by evaluating the reactivity based on the surface area, and the packing between the particles (TiO ₂ primary particles) constituting the titanium oxide powder is dense. case, the diffusion of Ba ^{2 +} of the interior of the TiO ₂ agglomerates the primary particles are aggregated is interference, it was found that the reaction tends to be uneven.

The degree of packing of the TiO ₂ primary particles can be known from the pore diameter distribution of the titanium oxide powder as a raw material, and the pore diameter distribution can be investigated by the pore volume (BJH method). there was. In addition, when pore volume is calculated | required by BJH method, it is supposed that the volume of the pore about 1 to several tens of diameters is usually calculated | required.

Based on these findings, further experiments and studies continued to complete the present invention.

That is, the manufacturing method of the perovskite complex oxide of the present invention,

As a method for producing a barium titanate-based perovskite-type composite oxide represented by general formula ABO ₃ ,

A reaction step of adding and reacting barium hydroxide to a solution containing at least titanium oxide powder;

The titanium oxide powder is characterized in that a titanium oxide powder having a pore volume of 0.38 mL / g or more and a specific surface area of 250 m ² / g or more is used.

In the perovskite complex oxide produced by the present invention, part of Ba constituting the A site may be substituted with Sr and / or Ca.

Moreover, in the manufacturing method of the perovskite complex oxide of this invention, it is preferable to further provide the process of heat-processing the perovskite complex oxide produced | generated at the said reaction process.

The method for producing a perovskite-type composite oxide represented by general formula ABO ₃ of the present invention includes a reaction step of adding and reacting barium hydroxide to a solution containing at least titanium oxide powder, and at the same time, the titanium oxide described above. As the powder, a titanium oxide powder having a pore volume of 0.38 mL / g or more and a specific surface area of 250 m ² / g or more is used, so that a fine powder having a specific surface having a larger specific surface area than that of a perovskite composite oxide obtained by a conventional liquid-liquid reaction is obtained. It is possible to obtain a lobedite complex oxide.

That is, when a titanium oxide powder having a pore volume of 0.38 mL / g or more and a specific surface area of 250 m ² / g or more is used, a larger specific surface area is compared with using a titanium oxide selected by focusing only on the specific surface area (SSA). It is possible to efficiently produce a perovskite-type composite oxide having a compound without requiring a particularly complicated manufacturing process.

In addition, in this invention, the pore volume prescribed | regulated with respect to a titanium oxide powder is a value calculated | required by the BJH method, and a specific surface area is a value calculated | required by the BET method.

Moreover, according to this invention, it is also possible to manufacture the perovskite type | mold 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 by adjusting a characteristic. The perovskite-type composite oxide having a compound can be efficiently produced.

In addition, the component raw material of Sr and / or Ca substituted with Ba may be included in the titanium oxide slurry, and may be added to the titanium oxide slurry prior to or simultaneously with barium hydroxide immediately before the reaction step.

In addition, by using barium hydroxide not containing hydrated water as barium hydroxide, it is possible to directly add solid barium hydroxide to a slurry in which titanium oxide powder or the like is dispersed, thereby simplifying the manufacturing process. In addition, when barium hydroxide containing no hydrated water is added to the titanium oxide slurry while being solid, the temperature rises due to the heat of dissolution, thereby facilitating the synthesis reaction.

In addition, in the present invention, the perovskite-type composite oxide having high crystallinity can be obtained by increasing the c / a axis ratio by heat-treating the perovskite-type composite oxide produced in the reaction step.

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 a pore volume of 0.38 mL / g or more and a specific surface area of 250 m ² / g or more is used, even after a heat treatment step that is a step of growing grains and improving crystallinity, It is possible to obtain a perovskite-type composite oxide having sufficiently fine and large specific surface area and high c / a axis ratio and high crystallinity.

1 is a view showing the relationship between the specific surface area of the BaTiO ₃ powder obtained by perform a specific surface area and the reaction of titanium (TiO ₂₎ oxide powder used as the Ti raw material according to an embodiment of the present invention (Example 1).
FIG. 2 is a diagram showing the relationship between the pore volume of the titanium oxide (TiO ₂ ) powder used as the Ti raw material and the specific surface area of the BaTiO ₃ powder obtained by causing the reaction in one embodiment (Example 1) of the present invention.
Figure 3 is a table 1 of the titanium oxide of the No.2 and No.7 (TiO ₂₎ the relationship of c / a axial ratio of the BaTiO ₃ powder, the specific surface area after calcination of the BaTiO ₃ powder produced by using the powder and crystal It is a figure which shows.

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 and pore volumes as shown in Table 1 were prepared. Each of titanium oxide addition (TiO ₂₎ a specific surface area of the powder is a BET method and a pore volume is a value obtained by measuring by the BJH method.

Then, 7.40 kg of TiO ₂ powders No. 1 to No. 9 in Table 1 and 19.4 L (liter) of pure water were added to the reactor, followed by stirring with a stirrer to prepare a slurry.

Next, after heating this slurry to 70 degreeC (preferably 50 degreeC or more), and adding a barium hydroxide (Ba (OH) ₂ ) which does not have hydration water so that it may become a predetermined Ba / Ti ratio, Barium titanate (BaTiO ₃ ) was synthesized by heating and stirring for 1 hour to maintain the temperature at 80 ° C. or higher, and the resulting slurry was dried to obtain BaTiO ₃ powder (perovskite-type composite oxide powder).

Then, the specific surface area of the obtained BaTiO ₃ powder was measured by the BET method. The results are shown in Table 1.

Further, X-ray diffraction of the obtained BaTiO ₃ powder was performed to investigate the residual state of Ba (OH) ₂ . The results are also shown in Table 1 together.

In addition, the relationship between the specific surface area (SSA) of the TiO ₂ powder used as the raw material and the specific surface area (SSA) of the BaTiO ₃ powder produced (synthesized) by reacting as described above is shown in FIG. The relationship between the pore volume of ₂ powder and the specific surface area of the produced (synthesized) BaTiO ₃ powder is shown in FIG. 1 and 2, number 1 to 9 attached in the vicinity of the plotted data is a number indicating the TiO ₂ powder in No.1 ~ 9 shown in Table 1.

As apparent from Table 1 and Figs. 1 and 2, when the No. 1 to No. 4 TiO ₂ powders of Table 1 were used, the specific surface area (SSA) was 307 to 315 m ² / g, and No of Table 1 In spite of being equivalent to the TiO ₂ powders of 0.5 to No. 9, it was confirmed that the specific surface area (SSA) of the obtained BaTiO ₃ powder was reduced to 10 to 44 m ² / g.

It was also confirmed that Ba (OH) _{2 as an} unreacted substance remained.

On the other hand, when TiO ₂ powders No. 5 to No. 9 in Table 1 were used, it was confirmed that BaTiO ₃ powders having fine grains and high crystallinity were obtained. It was also confirmed that Ba (OH) _{2 as an} unreacted substance did not remain.

This is because Ba (OH) ₂ diffuses to the inside of the aggregate of TiO ₂ particles by using a TiO ₂ powder having a large pore volume (0.38 mL / g or more) even if the specific surface area is equivalent to Nos. 1 to 4 in Table 1. This is because the reaction proceeded sufficiently.

<Example 2>

The final composition of (Ba Ca _{0 .95 0 .05)} TiO ₃ so that the titanium oxide (TiO ₂₎ powder (No.7 of the TiO ₂ powder shown in Table 1), calcium carbonate (CaCO ₃₎ powder, barium hydroxide (Ba ( OH) ₂ ) Each raw material of powder was weighed.

Then, the same manner as in Example 1 TiO ₂ powder added to (No.7 of the TiO ₂ powder shown in Table 1) and a CaCO ₃ powder, pure water to the reactor, and at a time of heating while stirring with a stirrer to 70 ℃, Barium hydroxide (Ba (OH) ₂ ) containing no hydrated water was added thereto, followed by stirring for 1 hour at 80 ° C or higher while stirring to obtain a (Ba, Ca) TiO ₃ slurry. Thereafter, the slurry was dried to obtain a (Ba, Ca) TiO ₃ powder.

The obtained (Ba, Ca) TiO ₃ powder had a specific surface area substantially the same as that of BaTiO ₃ produced (synthesized) using TiO ₂ powder of No. 7 in Table 1 of Example 1, and the composition (Ba _0.95) Ca _0.05) fine powder matching _{TiO 3 ((Ba 0 .95 Ca} 0 .05) TiO 3) it was confirmed that the powder.

It was also confirmed that Ba (OH) _{2 as an} unreacted substance did not remain.

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, and other salts such as calcium acetate and calcium nitrate, and hydroxides (calcium hydroxide), for example. It is also possible to use.

<Example 3>

The final composition (Ba _{0 .95 0 .05} Sr) TiO ₃ is such that TiO ₂ powder (No.7 of the TiO ₂ powder shown in Table 1), strontium carbonate (SrCO ₃₎ powder, barium hydroxide (Ba (OH) ₂₎ Each raw material of the powder was weighed.

Then, the same manner as in Example 1 In a (No.7 of the TiO ₂ powder shown in Table 1) and a SrCO ₃ powder and the pure TiO ₂ powder to the reactor, and at a time of heating while stirring with a stirrer to 70 ℃, Barium hydroxide (Ba (OH) ₂ ) containing no hydrated water was added thereto, followed by stirring for 1 hour at 80 ° C. or higher while stirring to obtain a (Ba, Sr) TiO ₃ slurry. Thereafter, the slurry was dried to obtain a (Ba, Sr) TiO ₃ powder.

The obtained (Ba, Sr) TiO ₃ powder had a specific surface area substantially the same as that of BaTiO ₃ produced (synthesized) using TiO ₂ powder of No. 7 in Table 1 of Example 1, and the composition (Ba _0.95 Ca) _0.05) fine powder matching _{TiO 3 ((Ba 0 .95 Sr} 0 .05) TiO 3) it was confirmed that the powder.

It was also confirmed that Ba (OH) _{2 as an} unreacted substance did not remain.

In addition, in Example 3, strontium carbonate (SrCO ₃ ) powder was used as the Sr source, but the Sr source is not limited to strontium carbonate (SrCO ₃ ) powder. For example, other salts such as strontium nitrate or hydroxide (hydroxyl) Strontium) or the like.

<Example 4>

Example 1 Table No.2 of the TiO ₂ powder of one of BaTiO produced using a (the pore volume that do not satisfy the requirements of the present invention of 0.22mL / g TiO ₂ powder) ₃ powder and, No.7 of TiO ₂ BaTiO ₃ powder produced using a powder (TiO ₂ powder having a pore volume of 0.48 mL / g satisfying the requirements of the present invention) was heat-treated by using a heat treatment furnace at different temperature conditions in the range of 800 to 1000 ° C. (Calcination) was performed.

The specific surface area of the BaTiO ₃ powder after heat treatment (after calcination) was measured by the BET method. In addition, the lattice constant was measured using X-ray diffraction (XRD), and the c / a axis ratio was calculated.

The relationship between the specific surface area (SSA) of BaTiO ₃ powder after heat treatment (after calcination) and the c / a axis ratio of the crystal is shown in FIG. 3.

Figure 3 As is clear from, the pore volume is 0.38mL / g or more (0.48mL), manufacturing (synthesis) using TiO ₂ powder (No.7 of the TiO ₂ powder) satisfying the requirements of the present invention, heat treatment (calcination) a BaTiO ₃ powder, and a pore volume of 0.22mL / g, TiO ₂ powder, which does not satisfy the requirements of the present invention produced (synthesized) by using the (TiO ₂ powder No.2), and heat treatment ( Compared with calcined BaTiO ₃ powder, it was confirmed that c / a-axis ratio is large and crystallinity becomes high.

3 shows that with the grain growth (specific surface area falls), c / a-axis ratio becomes large and crystallinity tends to improve.

In addition, the present invention is not limited to the above embodiment, and the solid content concentration of the slurry containing the titanium oxide (TiO ₂ ) powder to be used for the reaction, the reaction temperature and the reaction time when the reaction is added by adding the barium hydroxide to the slurry Conditions, the range and pore volume of the specific surface area of the titanium oxide powder as a raw material, the substitution ratio when a part of the A site is replaced with Sr and / or Ca, the conditions when the heat treatment of the barium titanate produced in the reaction step, etc. It is possible to add various applications and modifications within the scope of the invention.

Claims (3)

As a method for producing a barium titanate-based perovskite-type composite oxide represented by general formula ABO ₃ ,
A reaction step of adding and reacting barium hydroxide to a solution containing at least titanium oxide powder;
A method for producing a perovskite composite oxide, characterized in that titanium oxide powder having a pore volume of 0.38 mL / g or more and a specific surface area of 250 m ² / g or more is used as the titanium oxide powder. The method of claim 1,
A part of Ba which comprises A site is substituted by Sr and / or Ca, The manufacturing method of the perovskite type | mold composite oxide. The method according to claim 1 or 2,
A process for producing a perovskite complex oxide, further comprising the step of heat treating the perovskite complex oxide produced in the reaction step.

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