| 摘要 |
PURPOSE:To provide a silicon nitride-based sintered compact which undergoes slight deterioration of the strength in the temp. range from room temp. to a high temp. and has excellent oxidation resistance. CONSTITUTION:A compact consisting of 70-97mol% silicon nitride and 3-30mol%, in total, of the oxide of a group IIIa element of the periodic table and silicon oxide in 1:>=2 molar ratio is fired in a nonoxidizing atmosphere and the resulting sintered compact is held at a temp. between the softening temp. of glass formed at the grain boundaries of the sintered body and the crystallization temp. of the glass which is crystallized to y-RE2Si2O7 crystals (RE is the above- mentioned group IIIa element). The sintered compact is then held at a temp. between the crystallization temp. of the glass and the transition temp. of y- RE2Si2O7 which undergoes transition to beta-RE2Si2O7 to deposit y-RE2Si2O7 at the crystal boundaries of a silicon nitride crystal phase as the principal phase. |
