Shin-etsu Chemical Co., Ltd.

Masaki Watanabe

Hirofumi Fukuoka

Yoshiharu Konya

Masanori Fukuhira

Silicon nitride powder is prepared by nitriding metallic silicon powder in a nitriding gas atmosphere at a temperature of 1,000.degree. C.-1,500.degree. C. Midway the nitriding step, the nitrided product is heat treated in an inert non-oxidizing gas atmosphere or vacuum at a temperature higher than the nitriding temperature, but lower than 1,600.degree. C. The product is nitrided again, obtaining high .alpha.-content silicon nitride powder.

Preparation of high alpha-type silicon nitride powder

In a method for preparing a high .alpha.-type silicon nitride powder by adding to and mixing with metallic silicon powder a copper catalyst and nitriding the mixture in a non-oxidizing gas atmosphere containing nitrogen or ammonia at 1,000.degree. to 1,500.degree. C., the amount of copper catalyst is limited to from 0.05 % to less than 0.5 % by weight of copper based on the weight of the metallic silicon. There is obtained silicon nitride powder of high purity at low cost and high efficiency since the copper catalyst can be efficiently removed from the silicon nitride powder through conventional acid treatment.

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Annaka, Japan

Masaki Watanabe