JPH07291607A - Production of ceramic powder - Google Patents

Abstract

PURPOSE:To obtain ceramic powder having small particle diameters and a high specific surface area, being readily sintered and uniformly dispersed and having a complex perovskite structure free from composition deviation. CONSTITUTION:In producing ceramic powder having a perovskite structure of the general formula ABO3 type (with the proviso that A is an alkaline earth metal and is at least one or more of Ba, Sr, Mg and Ca; B is a tetravalent element of the titanium group and is at least one or more of Ti, Zr, Sn and Hf), a solution of an alkaline earth metal hydroxide is reacted with at least one of a hydroxide and an oxide sols of a tetravalent element of the titanium group in an amount equimolar with the alkaline earth element in a container by heating while stirring a grinding medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ABO ₃ type ceramic powder having a perovskite structure.

[0002]

2. Description of the Related Art The following various methods have been proposed as conventional methods for producing composite perovskite compound powder having an ABO ₃ type structure.

(A) A method of obtaining a target composite perovskite compound by mixing carbonate or oxide powders of the elements constituting the composite perovskite compound and then calcining the mixed powder at a temperature of 1000 ° C. or higher.

(B) Oxalates are reacted with metal ions of the elements constituting the composite perovskite compound to form a composite molecular compound precursor, and then the composite molecular compound precursor is calcined to obtain the target composite perovskite compound. How to get.

(C) After catechol and metal ions of the elements constituting the complex perovskite compound are reacted to form a complex molecular compound precursor, the complex molecular compound precursor is calcined to obtain the target complex perovskite compound. Method.

(D) A method for obtaining a composite perovskite compound by a sol-gel reaction using an alkoxide of an element constituting the composite perovskite compound.

(E) The purpose is to subject a hydroxide of an alkaline earth metal and a hydroxide or oxide sol of a tetravalent titanium group element constituting a composite perovskite compound to a hydrothermal reaction under high temperature, high pressure and sealing conditions. To obtain the composite perovskite compound of. For example, the reaction when the tetravalent titanium group element is Ti is as follows.

Me ⁺² + Ti (OH) ₆ ^-2 → Me
TiO ₃ + 3H ₂ O (provided that Me ^{+2 is an} alkaline earth metal ion) In the present production method, the molar amount of the tetravalent titanium group element hydroxide or oxide sol is larger than that of the tetravalent titanium group element hydroxide or oxide sol. Add an amount of alkaline earth metal hydroxide to make Ti (O
H) ₆ ^-2 complex is formed and the Ti (OH) ₆ ^-2 complex is reacted with an alkaline earth metal ion to increase the reaction yield. After the reaction is completed, excess alkaline earth metal ions are washed with pure water and removed.

[0009]

However, each of the above manufacturing methods has the following problems.

In the production method of (a), since powders of oxides or carbonates of elements constituting the composite perovskite compound are mixed, it is impossible to disperse them uniformly at the molecular level. In addition, it is necessary to pulverize the agglomerates obtained by calcining the mixed powder at a high temperature of 1000 ° C. or higher using a pulverizer having a large shearing force. Was mixed as an impurity in the complex perovskite compound.

In the production method of (b), the aggregate after the composite molecular compound precursor obtained by the reaction with the oxalate is calcined at high temperature is treated with shearing force in the same manner as in (a). It was necessary to carry out the pulverization process using a large pulverizer, and at this time, the abrasion material of the inner wall of the pulverizer or the media was mixed into the complex perovskite compound as an impurity. In addition, the optimum pH for forming oxalate may differ between the elements forming the A site of the composite perovskite, and in such a case, a composite molecular compound precursor having a different composition ratio than the target may be formed. It was Furthermore, in order to suppress dissolution of the obtained composite molecular compound precursor in water, it is necessary to add a large amount of an organic solvent such as ethyl alcohol.
This increased the BOD in the filtered waste liquid.

Also in the production method of (c), the aggregate after the composite molecular compound precursor obtained by the reaction with catechol is calcined at high temperature has a large shearing force as in (a). It is necessary to perform a pulverization process using a pulverizer, and at this time, the abrasion material of the inner wall of the pulverizer or the media is mixed as an impurity in the complex perovskite compound.

In the method (d), the alkoxide of Ti, such as Ti (OC ₃ H ₇ ) _4, is relatively inexpensive, but the alkoxides of other elements constituting the composite perovskite compound are very expensive. It was not suitable for mass production. Further, the alkoxide of an alkaline earth metal ion has a small solubility in a general organic solvent, and it has been impossible to increase the concentration of the complex perovskite compound and improve the production efficiency. Further, a special reaction device capable of controlling the atmosphere is required, and the reaction device itself becomes expensive.

In the production method of (e), the equipment cost is high because a reactor which can withstand high pressure is required.

When the excess alkaline earth metal ions are removed by washing after completion of the reaction, a part of the excess alkaline earth metal ions reacts with carbon dioxide gas in the air to form a sparingly soluble carbonate, resulting in a reaction. It remains in the composite perovskite compound powder obtained in. Therefore, if a weak acid is used to remove the carbonate, a part of the complex perovskite compound powder is dissolved together with the alkaline earth metal carbonate, and the complex perovskite compound powder deviated from the target molar ratio. Became.

Therefore, an object of the present invention is to solve the above problems and to have a composite perovskite structure which has a small particle size, a large specific surface area, is easily sinterable, and is uniformly dispersed and has no composition deviation. It is to provide a method for producing ceramic powder.

[0017]

In order to achieve the above object, the method for producing a ceramic powder according to the present invention comprises a general formula A
BO ₃ type (where A is an alkaline earth metal element, Ba, S
At least one of r, Mg, and Ca, and B is 4
In producing a ceramic powder having a perovskite structure of at least one of Ti, Zr, Sn, and Hf which is a valent titanium group element, a solution of an alkaline earth metal hydroxide and the alkaline earth metal It is characterized in that an equimolar amount of at least one kind of hydroxide or oxide sol of tetravalent titanium group element is reacted by heating while stirring the grinding media in the container.

Further, the hydroxide of the tetravalent titanium group element is
The water-soluble inorganic compound of the tetravalent titanium group element is reacted with caustic, and the oxide sol of the tetravalent titanium group element is obtained by hydrolyzing the water-soluble inorganic compound of the tetravalent titanium group element. And at least one of hydrolyzed organometallic compounds of the tetravalent titanium group element.

Further, it is characterized in that the reaction is carried out by heating to a temperature of 60 to 95 ° C. in a closed container.

Further, it is characterized in that at least one kind of caustic alkali or an organic amine compound is added in an amount of 1 to 4 mol per 1 mol of a tetravalent titanium group element and reacted.

After the reaction, the carbonate ion and the dispersant are added.

[0022]

In the present invention, an equimolar amount of a hydroxide of an alkaline earth metal is reacted with at least one of a hydroxide of a tetravalent titanium group element or an oxide sol.
Therefore, unlike the case of the conventional hydrothermal reaction, it is not necessary to remove the excess alkaline earth metal element by washing to adjust the molar ratio.

Further, in the present invention, the pulverized media are reacted while being stirred. Therefore, the reaction efficiency is increased by the mechanochemical action due to the shearing energy generated on the collision surface by the collision of the media. Furthermore, since the composite perovskite compound powder produced by the method of the present invention is a crystalline oxide, it shows a tendency to agglomerate as well although it is not as cohesive as amorphous hydroxide, but it is This agglomeration can be prevented by stirring and adding a dispersant.

Further, since the reaction is carried out at a temperature of 60 to 95 ° C., the pressure in the reaction vessel never exceeds 1 atm. Therefore, unlike the case of the manufacturing method utilizing the hydrothermal reaction, a high-pressure resistant reaction container is not required, and the reactor becomes inexpensive.

Further, the formation of insoluble carbonate of an alkaline earth metal element can be prevented by causing the reaction with the carbon dioxide gas in the air in a closed state without contact.

In the present invention, instead of the hydroxide of the alkaline earth metal element, a caustic alkali or an organic amine compound is added to form a Ti (OH) ₆ ^-2 complex. Therefore, after the reaction is completed, the toxic element Ba ⁺²
Need not be collected and processed. Moreover, since the caustic alkali and the organic amine compound to be added are inexpensive, the production cost of the composite perovskite compound powder can be reduced.

Further, since the powder of the complex perovskite compound produced by the method of the present invention is fine, some of it is dissolved and the alkaline earth metal element ions are eluted. By reacting the eluted alkaline earth metal element ions with carbonate ions to generate an insoluble alkaline earth metal carbonate salt, it is possible to prevent the deviation of the molar ratio of the obtained composite perovskite compound.

[0028]

EXAMPLES Examples of the method for producing ceramic powder of the present invention will be described below.

First, Ti (O) which is an alkoxide of Ti
1.0 mol of C ₃ H ₇ ) ₄ was dissolved in an isopropyl alcohol (hereinafter referred to as IPA) solution to prepare a 1.0 mol / L diluted solution of alkoxide. Next, this diluted alkoxide solution was dispensed so that the amount of Ti would be 0.1 mol and transferred to a beaker. After that, IPA was added to the collected alkoxide diluted solution to make it about 200 cc, and 180 cc of IPA solution containing 10% pure water was slowly added to hydrolyze while heating to 45 to 55 ° C. on a hot plate. . After hydrolysis, the pH was adjusted to 9 by adding aqueous ammonia to prepare a Ti oxide sol.

Similarly, Zr which is an alkoxide of Zr
Using (OC ₄ H ₉ ) ₄ as a starting material, a Zr oxide sol was prepared.

Further, each alkoxide diluted solution was dispensed so that Ti and Zr were each 0.05 mol and transferred to a beaker. Then, IPA was added to the separated alkoxide diluted solution to make it about 200 cc, and 180 cc of IPA solution containing 10% of pure was slowly added thereto while heating at 45 to 55 ° C. on a hot plate for hydrolysis. After the hydrolysis, ammonia water was added to adjust the pH to 9 to prepare a Ti / Zr composite oxide sol.

Next, so that the composition ratio shown in Table 1 is obtained,
Oxide sol of tetravalent titanium group element, hydroxide of alkaline earth metal element, NaOH and pure water 500 cc, diameter 2
500 cc of PSZ boulders of mm was put into a reaction container having an inner volume of 2000 cc with urethane stuck inside. Then PSZ
Set a sealed lid with an impeller for high-speed stirring in the reaction vessel, fix the reaction vessel in an oil bath, and
Z was reacted at 85 ° C. for 3 hours while stirring at high speed.

After completion of the reaction, 2 mol% of Na ₂ CO ₃ and 0.01 wt% of EDTA were added to the produced composite perovskite compound, and the mixture was stirred at a low speed for 30 minutes. Then, the reaction container was taken out from the oil bath and cooled to room temperature, and then the reaction product was collected and washed with pure water to remove Na ⁺ to obtain a composite perovskite compound powder.

[0034]

[Table 1]

Next, the obtained composite perovskite compound was subjected to X-ray diffraction (XRD) analysis, specific surface area (SS) measurement, and chemical analysis of molar ratio. The results are shown in Table 2. In addition, the sample No. Using the transmission analysis electron microscope, the composite perovskite compound of No. 2 was subjected to random molar ratio analysis at 10 spots with a spot diameter of 3 μm. The results are shown in Table 3.

[0036]

[Table 2]

[0037]

[Table 3]

As shown in Table 2, as a result of the XRD analysis, the sample No. obtained by the manufacturing method of the present invention was tested. The composite perovskites 1 to 3 are BaTiO ₃ and (BaSr) TiO _{3 respectively.}
And a cubic single phase of Ba (TiZr) O ₃ . As a result of the SS measurement, the sample No. The powders 1 to 3 have a specific surface area of about 40 m ² / g, which is 10 times or more that of the powder obtained by calcination and pulverization of the conventional carbonate or oxide powder. The obtained composite perovskite compound is shown to be a very fine powder. In addition,
The particle size converted from the value of SS is 3 nm, which is almost the same as the crystal particle size of 4 nm calculated from the diffraction width of XRD, and the particles are primary particle equal crystal particles. Moreover, according to the result of electron microscope observation, it has been found that primary particles of several nm are aggregated to form secondary particles of 0.1 to 0.3 μm. Further, the sample No. A chemical analysis of the molar ratios of the composite perovskite compound powders 1 to 3 showed that the compounds as charged were obtained within the analytical error range.

Further, as shown in Table 3, the sample No. The result of randomly analyzing the composite perovskite compound powder of No. 2 with a transmission analysis electron microscope at 10 spots with a spot diameter of 3 μm also shows a molar ratio close to the charged amount.

From the above results, according to the method for producing a ceramic powder of the present invention, a composite perovskite powder which is uniformly dispersed at the composition ratio as charged and has a large specific surface area and high surface activity is obtained.

In the above embodiment, Ti (OC ₃ H ₇ ) ₄ which is an organometallic compound of tetravalent titanium group element is used.
Alternatively, an oxide sol obtained by hydrolyzing Zr (OC ₄ H ₉ ) ₄ is reacted with a hydroxide of an alkaline earth metal, but the present invention is not limited to this.
That is, a hydroxide obtained by reacting a water-soluble inorganic compound of a tetravalent titanium group element with caustic or a hydrolyzed oxide sol, or an organometallic compound such as an alkoxide of a tetravalent titanium group element is used. At least one of the hydrolyzed oxide sols can be appropriately reacted with a hydroxide of an alkaline earth metal.

As the water-soluble inorganic compound of tetravalent titanium group element, chloride, oxychloride, nitrate, sulfate and the like can be used. Examples of the tetravalent titanium group organometallic compound include alkoxides such as titanium isopropoxide, titanium butoxide, titanium ethoxide, dibutoxy-ditriethanolaminatotitanium, and dibutoxy (2-hydroxyethylaminoethoxy) titanium, and other alkoxides. Ti organic compounds can be used. Also,
The same applies to other tetravalent titanium group elements other than Ti as in the case of Ti organic compounds such as Ti alkoxide.

Further, in the above embodiment, NaOH is added to form the Ti (OH) ₆ ^-2 complex, but the present invention is not limited to this. That is, Na
In addition to OH, caustic alkali such as KOH and LiOH and NH ₄
OH or aliphatic amine such as methylamine, dimethylamine, trimethylamine, ethylamine, o-, m
Aromatic amines such as-, p-toluidine and N, N-dimethylbenzylamine can be used as appropriate.

Further, in the above-mentioned Examples, Na ₂ CO ₃ was added after completion of the reaction to precipitate the complex perovskite compound which was dissolved in a small amount, but the present invention is not limited to this. That is, in addition to Na ₂ CO ₃ , carbonates such as K ₂ CO ₃ , Li ₂ CO ₃ and (NH ₄ ) ₂ CO ₃ can be used as appropriate.

[0045]

As is apparent from the above description, the method for producing a ceramic powder according to the present invention employs an equimolar amount of a hydroxide of an alkaline earth metal and a hydroxide or oxide of a tetravalent titanium group element. At least one of the product sol is reacted with the grinding media while stirring, and the product is ground simultaneously with the reaction. Therefore, it is possible to obtain a ceramic powder having a composite perovskite structure which has a small particle size, a large specific surface area, is easily sinterable, and is uniformly dispersed without compositional deviation.

Further, since the reaction is carried out in the closed container at a temperature of 60 to 95 ° C., the pressure in the reaction container does not become 1 atm or more, and the high withstand pressure as in the case of the manufacturing method utilizing the hydrothermal reaction is obtained. The reactor is inexpensive because it does not require a reaction vessel.

Claims (5)

[Claims] 1. The general formula ABO ₃ type (wherein A is an alkaline earth metal element and at least one or more of Ba, Sr, Mg, and Ca is used, and B is a tetravalent titanium group element, Ti or Z.
At least one of r, Sn, and Hf) in the production of ceramic powder having a perovskite structure, a solution of a hydroxide of an alkaline earth metal, and tetravalent titanium in an equimolar amount with the alkaline earth metal. A method for producing a ceramic powder, which comprises reacting at least one of a hydroxide of a group element or an oxide sol with stirring while heating a grinding medium in a container. 2. The hydroxide of a tetravalent titanium group element is
A water-soluble inorganic compound of a tetravalent titanium group element is reacted with caustic, and an oxide sol of a tetravalent titanium group element is obtained by hydrolyzing the water-soluble inorganic compound of a tetravalent titanium group element. And at least one of those obtained by hydrolyzing the organometallic compound of the tetravalent titanium group element,
The method for producing a ceramic powder according to claim 1, wherein 3. The method for producing a ceramic powder according to claim 1, wherein the reaction is carried out by heating to a temperature of 60 to 95 ° C. in a closed container. 4. The ceramic according to claim 1, wherein 1 to 4 mol of at least one of caustic alkali and an organic amine compound is added to 1 mol of a tetravalent titanium group element and reacted. Powder manufacturing method. 5. The method for producing a ceramic powder according to claim 1, wherein carbonate ions and a dispersant are added after the reaction is completed.