公开(公告)号：US5173458A

公开(公告)日：1992-12-22

申请号：US810723

申请日：1991-12-18

申请人： Takao Nishioka ,  Kenji Matsunuma ,  Koichi Sogabe ,  Tomoyuki Awatsu ,  Masaya Miyake ,  Takehisa Yamamoto ,  Akira Yamakawa

发明人： Takao Nishioka ,  Kenji Matsunuma ,  Koichi Sogabe ,  Tomoyuki Awatsu ,  Masaya Miyake ,  Takehisa Yamamoto ,  Akira Yamakawa

IPC分类号： C04B35/593

CPC分类号： C04B35/5935

摘要： Disclosed is a silicon nitride sintered body produced by subjecting a green compact of a mixed powder composed of 1) a silicon nitride powder having a percentage .alpha. crystallization of 93% or more and a mean grain diameter of 0.7 .mu.m or less and 2) 5 to 15% by weight in total of a first sintering aid selected from among rare earth element, yttrium oxide and lanthanide oxides and a second sintering aid consisting of aluminum oxide or nitride and at least one selected from among oxides and nitrides of Mg, Ca and Li, to primary sintering in a nitrogen gas atmosphere under a pressure of 1.1 atm or less at 1500.degree. to 1700.degree. C.; and subjecting the sintered body to secondary sintering in a nitrogen gas atmosphere under a pressure of 10 atm or more at the primary sintering temperature or below, thereby giving a sintered body wherein the relative density of the sintered body is 99% or more and the precipitation ratio of an .alpha.-Si.sub.3 N.sub.4 (including .beta.'-sialon) crystal phase ranges from 1:3 to 1:8 in terms of the peak intensity ratio in X-ray diffraction.