| 摘要 |
A silicon nitride sintered body wherein a number of grain boundaries of Si3N4 per a length of 10 mu m is not more than 20 when measured along a straight line drawn in an arbitrary section of the silicon nitride sintered body. A process is disclosed for producing such a silicon nitride sintered body, which includes the steps of grinding and mixing a raw material of silicon nitride and not more than 0.3 wt. % of Al when calculated as Al2O3, shaping the mixture, and firing the shaped body. The silicon nitride sintered body involves not only ordinary silicon nitride sintered bodies, but also vapor deposited films of silicon nitride formed by CVD or the like, flame sprayed films of silicon nitride formed by flame spraying, and the like.
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