Kyocera Corporation

Kazunori Koga

Kazumi Osamura

Kiyoshi Yokoyama

Makoto Yoshida

Shoji Kousaka

Tatsumi Maeda

Masafumi Matsunaka

Masaki Terazono

Shoji Kohsaka

Hideki Uchimura

Akira Saito

Disclosed is a silicon nitride sintered body comprising 85 to 99 mole % of .beta.-Si.sub.3 N.sub.4, 1 to 5 mole % as the oxide (M.sub.2 O.sub.3) of at least one compound of an element (M) selected from the group consisting of Sc, Vb, Er, Ho and Dy and less than 10 mole % of excessive oxygen (O.sub.2) based on the three components, wherein the excessive oxygen/M.sub.2 O.sub.3 molar ratio is lower than 2.

Silicon nitride sintered body and process for preparation thereof

Disclosed is a silicon nitride sintered body comprising 70 to 99 mole % of silicon nitride, 0.1 to 5 moles % of a rare earth element oxide and up to 25 moles % of silicon oxide and having a silicon oxide-to-rare earth element oxide molar ratio of from 2 to 25, wherein silicon nitride crystal grains have a fine acicular structure having an average particle major axis of up to 7 .mu.m and an average aspect ratio of at least 3.

Disclosed is a silicon nitride sintered body comprising 85 to 99 mol % of .beta.-Si.sub.3 N.sub.4, 1 to 5 mol % as the oxide (M.sub.2 O.sub.3) of at least one compound of an element (M) selected from the group consisting of Sc, Vb, Er, Ho and Dy and less than 10 mol % of excessive oxygen (O.sub.2) based on the three components, wherein the excessive oxygen/M.sub.2 O.sub.3 molar ratio is lower than 2.

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Kokubu, Japan

Kazunori Koga