Pressureless Sintered Dense Silicon Nitride Body Having High Toughness and High Strength without Rar

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The present invention relates to a high-toughness high-strength silicon nitride sintered body and a silicon nitride structural member manufactured by an atmospheric pressure sintering process which does not use a rare earth element. The crystal phase of silicon nitride is not less than 88 wt%, and a rare earth element or rare earth compound is not contained as a sintering aid. 1.5-4 wt% of Mg element converted to oxide, 0.5-2.5 wt% of Al element converted to oxide, 1-5 wt% of Ti element converted to oxide, and 1-4.5 wt% of Si element converted to oxide are contained necessarily as sintering aids. The weight ratio of Al element converted to oxide to Mg element converted to oxide is in the range of 1 : 1 to 1 : 2.5, the weight ratio of Al element converted to oxide to Si element converted to oxide is in the range of 1 : 1 to 1 : 3, and the weight ratio of Al element converted to oxide to Ti element converted to oxide is in the range of 1 : 1 to 1 : 4.5.COPYRIGHT KIPO 2018