JPH06649B2 - Method for producing fine dielectric particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing dielectric fine particles such as barium titanate fine particles, strontium titanate fine particles, and barium zirconate fine particles.

[Conventional technology]

The applicant of the present invention has filed Japanese Patent Application No. 57-147226 (a method for producing fine particles of barium titanate), Japanese Patent Application No. 57-151240 (a method for producing fine particles of calcium titanate) and Japanese Patent Application No. 57-156315 (production of fine particles of strontium titanate). Method), Japanese Patent Application No. 57-219540
In (Production method of barium zirconate fine particles) and the like, a method for producing dielectric fine particles by a wet synthesis method was proposed.

In these methods for producing dielectric fine particles, Ti) or Z
When chloride is used as the raw material of r),
The outline is as follows.

First, TiCl ₄ (or ZrCl ₄ , ZrOCl ₂ · 8H ₂ O, etc.) is hydrolyzed and then neutralized using an alkaline agent such as NaOH, KOH. Next, after adding Ba (or Ca, Sr, etc.) in an equimolar amount to TiCl ₄ , the pH is made strongly alkaline with an alkaline agent such as NaOH, KOH, and the mixture is heated and reacted. After that, washing with water by decantation, filtration and drying are carried out to obtain, for example, barium titanate BaTiO ₃ fine particles.

[Problems to be solved by the invention]

As described above, when the dielectric fine particles produced by using chloride as a raw material of Ti (or Zr) are measured with a fluorescent X-ray analyzer, a trace amount of Cl is detected. This Cl is considered to be derived from the titanium oxide (or zirconium chloride) that is the raw material. Since the presence of Cl may cause deterioration of reliability due to aging after processing into a capacitor, a ceramic molded product, etc., it is desirable that the amount of Cl be as small as possible. Further, even when used as a raw material for fine ceramics products, the presence of Cl may cause a problem.

The present invention provides a method for producing dielectric fine particles, which can solve the above problems.

[Means for solving problems]

In the present invention, a chloride of titanium or zirconium (for example, TiCl ₄ , ZrCl ₄ , ZrOCl ₂ · 8H ₂ O, etc.) is hydrolyzed in an aqueous solution, and then this aqueous solution is treated with an alkaline agent (NaOH, KOH).
Etc.) and make it alkaline with pH 7.1 or higher, and then rinse with water,
Decanting is performed to remove chlorine ions. Subsequently, at least one of water-soluble salts of barium, strontium and calcium is added and reacted in a strongly alkaline aqueous solution to obtain desired dielectric fine particles.

When the resulting dielectric particles are ABO ₃ (A: Ba, Sr, C
a, B: Ti, Zr), and can be applied to the production of not only a single system but also a composite system of fine particles.

As the water-soluble salt of barium, for example, Ba (N
_{O 3) 2, Ba (OH} ) 2, can be used _{BaCl 2, Ba (CH 3 COO} ) 2. Moreover, as the water-soluble salt of strontium, for example, Sr (NO ₃ ) ₂ , Sr (OH) ₂ , SrCl ₂ , Sr (CH ₃ COO) ₂ , and SrO can be used. As a water-soluble salt of calcium,
For example it is possible to use _{Ca (NO 3) 2, Ca} (OH) 2, CaCl 2, Ca (CH 3 COO) 2, CaO.

[Action]

In a method for producing fine dielectric particles using chloride as a raw material of titanium or zirconium, when chloride is conventionally hydrolyzed and neutralized with alkali, Cl remains in the form of TiOCl _2, etc., and Cl is crystallized during the synthesis reaction. It is taken in by or is adsorbed on the crystal surface and is not removed even by washing with water during the reaction.
There is a problem that Cl remains in the obtained dielectric fine particles. However, in the present invention, the solution after hydrolysis of chloride is not neutral, but is made alkaline, so that Cl is less likely to remain, and washing in water and decantation significantly increase Cl in the solution. Can be removed. Therefore, the residual amount of Cl in the obtained dielectric fine particles can be suppressed to be low.

〔Example〕

Example 1 NH ₄ OH was added to a solution prepared by dissolving 50 g of TiCl ₄ in 100 g of water to cause hydrolysis to bring the pH to 9.5. Then, the solution generated by this sedimentation is repeatedly washed with water and decanted to adjust the pH.
Was set to 7. Next, Ti in the solution was mixed with Ba in an approximately equimolar amount (0.95).
(OH) ₂ was added and the pH was adjusted to 14 with KOH solution. This solution was reacted at 90 ° C. for 3 hours, the formed precipitate was filtered, washed with water, and then dried at 100 ° C. for 1 day.

According to the result of X-ray diffraction analysis of the obtained fine particles, it was confirmed that the fine particles were BaTiO ₃ . The particle size was 200 to 300Å.

Example 2 To a solution of 50 g of TiCl ₄ dissolved in 200 g of water was added a NaOH solution for hydrolysis to bring the pH to 9.5. Then, washing with water and decantation are repeated on the solution in which this sedimentation is generated,
The pH was 7. Next, BaO was added, the pH was adjusted to 13.7 with a NaOH solution, and the mixture was reacted at 95 ° C for 2 hours. The generated precipitate was filtered, washed with water, and dried at 100 ° C for 1 day.

According to the result of X-ray diffraction analysis of the obtained fine particles, it was confirmed that the fine particles were BaTiO ₃ . The particle size was 200 to 300Å.

Next, Table 1 shows the results of measuring the residual chlorine content of the BaTiO ₃ fine particles obtained in Examples 1 and 2 by fluorescent X-ray analysis together with Comparative Example (pH of the solution immediately after hydrolysis is 7). Indicate. From this table, the solution after hydrolysis was made alkaline, washed with water and decanted.
It can be seen that it is effective in reducing the amount of residual chlorine in the TiO ₃ fine particles.

Example 3 NH ₄ OH was added to a solution prepared by dissolving 50 g of TiCl ₄ in 100 g of water to cause hydrolysis to bring the pH to 9.5. The solution in which this precipitate was formed was washed with water and decanted repeatedly to adjust the pH.
Was set to 7. Next, for the Ti of this solution, Sr / Ti = 1.
Sr (OH) ₂ with a molar ratio of 05 was added, and the pH was adjusted to 14 with a KOH solution. After this solution was reacted at 95 ° C for 4 hours, the formed precipitate was filtered, washed with water, and dried at 100 ° C for 1 day.

According to the result of X-ray diffraction analysis of the obtained fine particles, it was confirmed that the fine particles were SrTiO ₃ . The particle size was 100 to 200Å.

Example 4 To a solution of 50 g of TiCl ₄ dissolved in 200 g of water was added a NaOH solution for hydrolysis to bring the pH to 9.5. Then, the solution in which the sedimentation has occurred is repeatedly washed with water and decanted to adjust the pH.
Was set to 7. Next, an equimolar amount of SrCl ₂
Was added and the pH was adjusted to 14 with a NaOH solution. After reacting at 100 ° C for 3 hours, the formed precipitate was filtered and washed with water,
Dried for a day.

According to the analysis result by X-ray diffraction, the fine particles are SrTiO ₃
It was confirmed that

Next, Table 2 shows the results of measuring the residual chlorine content of the SrTiO ₃ fine particles obtained in Examples 3 and 4 by fluorescent X-ray analysis together with Comparative Examples (pH immediately after hydrolysis is 7). .

Example 5 NH ₄ OH was added to a solution prepared by dissolving 50 g of TiCl ₄ in 100 g of water for hydrolysis to adjust the pH to 9.5. Then, the solution in which this precipitation had occurred was repeatedly washed with water and decanted to adjust the pH to 7. Next, Ca (OH) ₂ with a molar ratio of 1.05 was added to Ti of this solution, and the pH was adjusted to 14 with a NaOH solution. After this solution was reacted at 95 ° C for 4 hours, the formed precipitate was filtered, washed with water, and dried at 100 ° C for 1 day.

According to the result of X-ray diffraction analysis of the obtained fine particles, it was confirmed that the fine particles were CaTiO ₃ . The particle size was 1 to 3 μm.

Example 6 A solution of 50 g of TiCl ₄ in 200 g of water was hydrolyzed by adding a NaOH solution to adjust the pH to 9.5. Then, the solution in which the sedimentation has occurred is repeatedly washed with water and decanted to adjust the pH.
Was set to 7. Next, CaCl _{2 in the same} molar amount as Ti in this solution
Was added and the pH was adjusted to 14 with a NaOH solution. This solution at 100 ℃ 3
After reacting for a time, the generated precipitate is filtered and washed with water,
It was dried at 100 ° C. for 1 day.

According to the analysis result by X-ray diffraction, the fine particles are CaTiO ₃
It was confirmed that

Next, Table 3 shows the results of measuring the residual chlorine content of the CaTiO ₃ fine particles obtained in Examples 5 and 6 by fluorescent X-ray analysis together with Comparative Examples (pH immediately after hydrolysis is 7). .

Example 7 40 ml was taken from a solution of 500 ml in which 55.74 g of ZrCl ₄ was dissolved in water, and LiOH was dissolved therein to hydrolyze the solution to adjust the pH.
It was set to 9.5. Then, the solution in which this precipitation had occurred was repeatedly washed with water and decanted to adjust the pH to 7. LiO Ba a (OH) ₂ · 8H ₂ O and 9.054g (Ba / Zr = 1.5) was added to the white suspension
The pH was adjusted to 14 with H solution. After reacting this solution at 98 ° C for 8 hours, the generated precipitate was decanted and filtered,
Dried.

According to the result of analyzing the obtained fine particles by X-ray diffraction, it was confirmed that the fine particles were BaZrO ₃ . The particle size was 2 to 3 μm. According to the result of measuring the residual chlorine amount by fluorescent X-ray analysis, it was confirmed that the residual chlorine amount in the BaZrO ₃ fine particles obtained by the present production method was significantly reduced.

〔The invention's effect〕

According to the present invention, since the amount of chlorine remaining in the dielectric fine particles is significantly reduced, the deterioration of characteristics due to chlorine does not occur, and a highly reliable capacitor, ceramic molded product, etc. can be provided. Further, it is only necessary to add a step of removing Cl, and the wet synthesis method proposed by the present applicant can be adopted as it is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidemasa Tamura Inventor Hidemasa Tamura 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-59-195574 (JP, A)

Claims (1)

[Claims] 1. Hydrolysis of titanium or zirconium chloride in an aqueous solution, and then once rendering the aqueous solution alkaline to remove chloride ions, and subsequently at least one of water-soluble salts of barium, strontium and calcium. And a reaction method in a strong alkaline aqueous solution.