| 摘要 |
PURPOSE:To improve strength at high temp. by subjecting a powdery raw material which consists of a powder mixture consisting of Si3N4 powder, spinel powder or powder mixture of MgO and Al2O3, and powder mixture of Y2O3 and one or more kinds among La2O3, CeO2, and Yb2O3 to compacting and then to sintering. CONSTITUTION:A powder mixture consisting of 1.5-6% (by weight, the same applies to the following) of either or both of spinel powder and powder mixture in which MgO and Al2O3 are blended in a molar ratio of 1 to 1, a sintering auxiliary in which the total content of 2-5% Y2O3 and one or more kinds selected from the group consisting of La2O3, CeO2, and Yb2O2 is regulated to 3.5-6.30% and the relations in Y2O3/(Y2O3+La2O3+CaO2+Yb2O3)<=0.8 are satisfied, and Si3N4 powder as the balance is compacted. The resulting green compact is sintered at 1650-1950 deg.C under an N2 atmosphere, by which an Si3N4 sintered compact minimal in reduction in strength at high temp. is obtained. |
