Birch, Stewart, Kolasch & Birch
Silicon nitride sintered body having excellent high-temperature strength and method of producing same
 A silicon nitride sintered body having a composition of 1.5-3.0 weight % of Y.sub.2 O.sub.3, 0.1-1.0 weight % of Al.sub.2 O.sub.3 and balance substantially Si.sub.3 N.sub.4, a weight ratio of Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 being 2.5 or more, which has a density of 3.0 g/cm.sup.3 or more and has a structure in which the minor axes of grains are substantially 6 .mu.m or less. This silicon nitride sintered body is produced by preparing a powder mixture containing Y.sub.2 O.sub.3 powder, Al.sub.2 O.sub.3 powder and silicon nitride powder in the above proportions, the silicon nitride powder having an oxygen content of 1.2 weight % or less, a specific surface area of 9-11 m.sup.2 /g and a metal impurity content of 200 ppm or less; and sintering the powder mixture at a temperature of 1900.degree.-2100.degree. C. and a pressure of 5 kg/cm.sup.2 G or more in a nitrogen atmosphere. 
Honda Giken Kogyo Kabushiki Kaisha Tosoh Corporation
C C
C04B C04B
inventional inventional
Toshihiko Kagehisa Yasunobu Toshiyuki
Arakawa Hamazaki Kawakami Mori