| 摘要 |
PURPOSE:To obtain a silicon nitride-based sintered compact having excellent mechanical strength at ordinary temperature advantageously to productivity and cost by sintering mixed powder composed of silicon nitride raw material powder, the first specific assistant and second specified assistant of a composition within a specific range under specified conditions in two stages. CONSTITUTION:A compact composed of mixed powder having a composition within an area [(85:15) to (95:5)mol% ratio of Si3N4: the first assistant and (90:10) to (98:2)mol% ratio of Si3N4: the second assistant] surrounded by points A, B, C and D in a ternary compositional diagram of the Si3N4-first assistant (Y2O3+CeO2 or CaO)-second assistant (one or two or more of Al2O3 and AlN) is primarily sintered in an N2 gas atmosphere at 1500-1700 deg.C under <=1.1atm so as to provide >=96% relative density of the sintered compact and then secondarily sintered in an N2 atmosphere at 1500-1700 deg.C under >=10atm so as to afford >=99% relative density of the sintered compact. The crystal phase in the sintered compact comprises both alpha-Si3N4 and beta'-sialon. |
