| 摘要 |
PURPOSE:To compatibilize the productivity and the mechanical properties of a sintered material by sintering a powdery mixture having a specific composition of Si3N4 having specific alpha-content and particle diameter, a 1st assistant consisting of Y2O3/MgO and a 2nd assistant consisting of Al2O3/AlN under specific sintering condition. CONSTITUTION:The objective sintered material containing both alpha-Si3N4 and beta-sialon in the crystal phase is produced by producing a green compact or a molding of a powdery mixture consisting of Si3N4 powder having alpha-content of >=93% and an average particle diameter of <=0.7mum, a 1st assistant consisting of Si3N4-Y2O3 and MgO and a 2nd assistant consisting of Al2O3-AlN and having a composition falling within the range encircled by lines connecting the points A to D in the triangular composition diagram of Si3N4 being the 1st assistant and the 2nd assistant (the compositional ratio of Si3N4: the 1st assistant is 85:15 to 95:5, and that of Si3N4: the 2nd assistant is 90:10 to 98:2 in terms of mol.%), subjecting the green compact, etc., to the primary sintering at 1400-1600'C in N2 gas atmosphere under <=1.1atm to get a sintered material having a relative density of 96-98.5% and then to the secondary sintering at 1400-1700 deg.C in N2 gas atmosphere under >=10atm to get a sintered material having a relative density of >=99.5%. |
