JPH11157845A - Production of ruthenium oxide powder and ruthenium multiple oxide powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce fine Ru oxide powder and Ru compound oxide powder having <=10 μm size and free from coarse particles. SOLUTION: Amorphous ruthenium oxide hydrate is deflocculated while dispersing in water or an org. solvent and it is dried and roasted to produce the objective Ru oxide powder. Amorphous ruthenium oxide hydrate is mixed with a compd. of at least one metal selected from among Pb, Bi, Ca, Sr, Ba and La, the mixture is deflocculated while dispersing in water or an org. solvent and it is dried and roasted to produce the objective Ru compound oxide powder. The roasting temp. is preferably 300-1,000 deg.C.

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 a Ru oxide powder and a Ru composite oxide powder for forming a thick film resistor paste.

[0002]

2. Description of the Related Art Ru oxide powders and Ru composite oxide powders are widely used as conductive materials for thick-film resistors because a resistor whose electrical resistance value changes gradually by changing the ratio of glass powder can be formed. ing.

In order to form a thick film resistor having a small resistance value distribution and good electrical characteristics, it is necessary that the Ru oxide powder and the Ru composite oxide powder are fine and free of coarse particles. As a raw material of a thick-film resistance paste having a small resistance value distribution and good electric characteristics, it is preferable that the particle diameter of the Ru oxide powder or the Ru composite oxide powder is 10 μm or less. As a method for producing such a Ru oxide powder, generally, an amorphous solution of ruthenium chloride is neutralized with an alkali, or a solution of an alkali metal ruthenate is neutralized and reduced with an alcohol or formic acid to form an amorphous form. It is produced by precipitating ruthenium oxide hydrate and roasting the amorphous ruthenium oxide hydrate at a high temperature.

The Ru composite oxide powder is prepared by mixing a Ru oxide with an oxide such as Pb, Bi, Ca, Sr, Ba, La, etc., and heat-treating the mixed oxide or an amorphous ruthenium oxide hydrate. It is manufactured by coprecipitating such an oxide and then roasting.

[0005]

However, in these production methods, a particle having a particle size of Ru oxide powder or Ru composite oxide powder which is greatly different depending on production conditions or other processing conditions is produced, or 10 μm Coarse particles exceeding 10 μm are likely to be generated, which causes deterioration of the electrical characteristics of the thick film resistor.

The present invention solves the above-mentioned problems of the prior art, and provides a method for producing a Ru oxide powder or a Ru composite oxide powder having a fine particle size of 10 μm or less and no coarse particles. The purpose is to do so.

[0007]

The present inventors have made amorphous ruthenium oxide hydrate or amorphous ruthenium oxide hydrate and at least one compound selected from the group consisting of Pb, Bi, Ca, Sr, Ba and La. Was found to solve the above-mentioned problem by dispersing and dispersing in water or an organic solvent, and then drying and roasting to complete the present invention.

That is, the first embodiment of the present invention is characterized in that amorphous ruthenium oxide hydrate is dispersed in water or an organic solvent to loosen agglomerates, and then dried and roasted. It is characterized by a method for producing a Ru oxide powder at a temperature of 300 to 1000 ° C.

In a second embodiment, the above-mentioned amorphous ruthenium oxide hydrate further comprises Pb, Bi, Ca, S
At least one compound selected from the group consisting of r, Ba, and La is mixed, disaggregated while dispersing in water or an organic solvent, and then dried and roasted. It is characterized by a method for producing a Ru composite oxide powder at 1000 ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION R as a raw material of a thick film resistor paste
It is desirable that the u oxide powder and the Ru composite oxide powder have a fine particle size, a small particle size distribution, and good dispersibility. This Ru oxide powder or Ru composite oxide powder is produced by heat-treating amorphous ruthenium oxide hydrate. In the course of this heat treatment, coarse particles may grow, and the resistance value of the thick film resistor may be increased. Increase the distribution,
In some cases, this may cause deterioration of electrical characteristics.

The present inventors have conducted intensive studies on the cause of the formation of the coarse particles of the Ru oxide powder and the Ru composite oxide powder. It was found that there was a difference in the formation of microcrystals of the Ru oxide powder and the Ru composite oxide powder depending on the portion, and this was responsible for the formation of coarse particles.

That is, amorphous ruthenium oxide hydrate is synthesized from a solution containing ruthenium by a wet method, but very fine particles are aggregated during this synthesis. It has been found that this local difference in the manner of aggregation causes coarse particles of the Ru oxide powder and the Ru composite oxide powder.

Therefore, in the present invention, the amorphous ruthenium oxide hydrate or the amorphous ruthenium oxide hydrate and P
b, Bi, Ca, Sr, Ba, a mixture with at least one compound selected from La, after dispersing in water or an organic solvent to disperse agglomeration, by drying and roasting, Agglomeration of the amorphous ruthenium oxide hydrate becomes uniform, and as a result, coarse particles are not generated during roasting. The amorphous ruthenium oxide hydrate used here may be one synthesized by any conventional synthesis method, and it is not necessary to strictly set synthesis conditions.

The dispersion medium for dispersing the amorphous ruthenium oxide hydrate and the mixture of the amorphous ruthenium oxide hydrate and the compound described above is preferably a water-soluble organic solvent such as water or alcohol. Further, a dispersant for accelerating the dispersion of amorphous ruthenium oxide hydrate can be added as required. Amorphous ruthenium oxide hydrate or a method of loosening agglomeration while dispersing a mixture of the amorphous ruthenium oxide hydrate and the compound described above is a general method used for dispersing a powder in a liquid phase. And a ball mill, an attritor, a bead mill and the like are preferable from the viewpoint of easy handling. In addition, aggregation is loosened while dispersing, and Pb, Bi, Ca, Sr, B
As a method for drying the amorphous ruthenium oxide hydrate mixed with a compound such as a and / or La, any conventional method can be used.

Further, in the production method of the Ru oxide powder and the Ru composite oxide powder, K,
A method has been proposed in which ions such as Na, Li and / or B are added to amorphous ruthenium oxide hydrate or a mixture of the amorphous ruthenium oxide hydrate and the compound described above. These ions may be added in the step of loosening the aggregation while dispersing the regular ruthenium oxide hydrate.

The roasting temperature of the amorphous ruthenium oxide hydrate or the mixture of the amorphous ruthenium oxide hydrate and the compound described above is preferably in the range of 300 to 1000 ° C., and the roasting temperature is 300 ° C. Below, the amorphous ruthenium oxide hydrate does not completely turn into RuO ₂ powder, while
If the temperature exceeds ℃, the particle size of the RuO ₂ powder becomes too large, and RuO ₂ is converted to RuO ₄ and volatilized, and the yield of RuO ₂ is reduced.

[0017]

Example 1 Amorphous ruthenium oxide hydrate obtained by reducing a K ₂ RuO ₄ solution with methanol was washed with water to remove impurities, and then 200 g of amorphous ruthenium oxide was added together with alumina balls having a diameter of 10 mm. Dispersed in a 2 liter ball mill for 40 hours, dried at 110 ° C.,
After roasting for a time, a Ru oxide powder was prepared.

Example 2 Amorphous ruthenium oxide hydrate obtained by reducing a K ₂ RuO ₄ solution with methanol was washed with water to remove impurities. Dispersed in a ball mill of 40 liters for 40 hours, dried at 110 ° C.,
After roasting for a time, a Ru oxide powder was prepared.

Example 3 Amorphous ruthenium oxide hydrate and lead oxide hydrate obtained by neutralizing a K ₂ RuO ₄ solution with a lead nitrate solution and nitric acid were washed with water to remove impurities. 200 g of amorphous ruthenium oxide hydrate and lead oxide hydrate were put into a 2 liter ball mill together with alumina balls having a diameter of 10 mm, dispersed for 40 hours, dried at 110 ° C., and then roasted at 600 ° C. for 2 hours to form a Ru composite. An oxide powder was prepared.

Example 4 Amorphous ruthenium oxide hydrate and lead oxide hydrate obtained by neutralizing a K ₂ RuO ₄ solution with a lead nitrate solution and nitric acid were washed with water to remove impurities. Ruthenium oxide hydrate and 200 g of lead oxide hydrate were put into a 2 liter ball mill together with alumina balls having a diameter of 10 mm and dispersed for 40 hours, then dried at 110 ° C., and then roasted at 800 ° C. for 2 hours to obtain a Ru composite oxide. Product powder was prepared.

Comparative Example 1 A powder of Comparative Example 1 was obtained in the same manner as in Example 1 except that the dispersion treatment was not performed by a ball mill.

Comparative Example 2 A powder of Comparative Example 2 was obtained in the same manner as in Example 2 except that the dispersion treatment was not performed by a ball mill.

Comparative Example 3 A powder of Comparative Example 3 was obtained in the same manner as in Example 3 except that the dispersion treatment was not performed by a ball mill.

Comparative Example 4 A powder of Comparative Example 4 was obtained in the same manner as in Example 4 except that the dispersion treatment was not performed by a ball mill.

The specific surface areas of the Ru oxide powder and Ru composite oxide powder prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were examined by a continuous flow method, and the SEM
As a result, the presence or absence and the number of coarse particles having a particle diameter of 1 μm or more were confirmed. Further, the Ru oxide powder and the Ru composite oxide were identified by an X-ray diffraction method. Tables 1 and 2 show the evaluation results.

[0026]

[Table 1]

[0027]

[Table 2]

Tables 1 and 2 show that in Examples 1 to 4 in which amorphous ruthenium oxide hydrate or amorphous ruthenium oxide hydrate and lead oxide hydrate were dispersed before drying, generation of coarse particles was not observed. In contrast, Comparative Examples 1 to 4 in which the specific surface area was large and thereby the average particle size was small, whereas coarse particles were generated in Comparative Examples 1 to 4 which were not dispersed before drying, the specific surface area was small and the average particle size was small. It turned out to be big. It was also found that the generation of coarse particles was more remarkable as the roasting temperature was higher.

[0029]

As described above, according to the present invention, there are no coarse particles which are liable to be generated by the conventional manufacturing method, and a fine particle size of 10 μm or less, a Ru oxide powder having a small particle size distribution, and a Ru composite oxide. Product powder can be manufactured.

Claims (4)

[Claims] 1. A method for producing a Ru oxide powder, comprising dispersing amorphous ruthenium oxide hydrate in water or an organic solvent to loosen agglomerates, drying and roasting. 2. The method for producing a Ru oxide powder according to claim 1, wherein the roasting temperature is 300 to 1000 ° C. 3. The method according to claim 1, wherein at least one compound selected from the group consisting of Pb, Bi, Ca, Sr, Ba and La is mixed with the amorphous ruthenium oxide hydrate.
Production method of u composite oxide powder. 4. The method according to claim 3, wherein the roasting temperature is 300 to 1000 ° C.