PRODUCTION OF SINTERED SILICON NITRIDE

摘要

PURPOSE:To obtain a large-sized and thick-walled sintered material having improved reliability by baking a formed mixture of silicon nitride and a sintering assistant under specific baking condition to eliminate the open pores of the formed article and proceeding the sintering without causing the sintering difference between the surface and the core parts at a temperature and a pres sure higher than those of the baking stage. CONSTITUTION:A powdery mixture composed of silicon nitride as a main component and a sintering assistant (e.g. Y2O3, La2O3 and Er2O3) is formed. The formed product is baked in nitrogen atmosphere having an inert gas content of >=50% and a total pressure of 0.1-2atm at 1500-1700 deg.C to eliminate the open pores of the formed material. The baked product is further baked in nitrogen atmosphere at a temperature and a pressure higher than those of the primary baking process to proceed the sintering without causing the sintering difference between the surface and the core parts.