| 摘要 |
PURPOSE:To improve strength at room temp. and high temp. by controlling the amt. of silicon nitride incorporated into the intergranular area of a silicon nitride crystal phase to specified proportion and by providing a crystal phase expressed by Si2N2O. CONSTITUTION:Oxides of group 3a elements in the periodic table (e.g. Y2O3), silicon oxide and silicon nitride by <30mol% are mixed, heated and molten to prepare glass. This glass is pulverized and added to the source material powder of silicon nitride, molded and calcined in a nonoxidative atmosphere. The sintered body thus obtd. is subjected to heat treatment to crystallize the intergranular material to precipitate a Si2N2O crystal phase. Thereby, the obtd. silicon nitride sintered body has a silicon nitride crystal phase and the intergranular phase containing at least group 3a elements. This intergranular phase contains silicon nitride component by <=30mol% to the total intergranular phase and a crystal phase expressed by Si2N2O. The sintered body thus obtd. is suitable as a high temp. material such as a heat engine. |
