| 摘要 |
PURPOSE:To obtain a sufficiently densified and sintered silicon nitride-based compact by sintering a calcined compact, consisting of silicon nitride and calcining assistant and having a gas-impermeable dense layer only on the surface part in an inert gas under conditions of a prescribed pressure and temperature according to hot isostatic pressing. CONSTITUTION:A mixture consisting of silicon nitride and a well-known calcining assistant, e.g. oxide, nitride, carbide, etc., of group IIIa elements, etc., of the periodic table is formed into a desired shape. Furthermore, the above- mentioned mixture is composed of, e.g. 20wt.% calcining assistant and the remainder of silicon nitride. The aforementioned compact is then calcined to prepare a calcined compact having a gas-impermeable dense outer layer formed thereon. The resultant calcined compact is subsequently sintered at 1600-2000 deg.C temperature under 100-2000 atm pressure in N2 atmosphere by hot isostatic pressing. Thereby, since high density can be provided in a hardly sinterable composition system or large-sized shape, e.g. a sintered compact of a system with hardly any assistant can be obtained in the sintered silicon nitride-based compact. |
