| 摘要 |
PURPOSE:To enhance strength of a silicon nitride sintered body at a high temp. by mixing at least tow kinds selected from among Y2O3, Er2O3, Tm2O3, Yb2O3 and Lu2O3 as a sintering adjuvant with Si3N4 powder and molding the mixture and heat-treating the molded body in the specified conditions and thereafter covering this molded body with glass and performing high-temp. hydrostatic pressing and sintering the molded body. CONSTITUTION:At least two kinds selected form among Y2O3, Er2O3, Tm2O3, Yb2O3 and Lu2O3 are added at about 8-13 wt.% as a sintering adjuvant to Si3N4 powder. The mixture is ground by a wet process and thereafter dried to obtain mixed powder. This dry powder is pressure-molded and the molded body is heat-treated at 1750-1950 deg.C in a N2 atmosphere of 9.5 atm. Thereafter this molded body is encapsulated with a glass capsule and deaerated and then high- temp. hydrostatic pressing is performed at 1850-1950 deg.C at 500-2000 atm and the molded body is sintered. The glass capsule is removed after sintering and furthermore the molded body is heated in a N2 atmosphere and crystallizing treatment is performed. An Si3N4 sintered body is obtained which has a high denseness and is excellent in hgih-temp. strength. |
