| 摘要 |
PURPOSE:To obtain a high strength and high toughness silicon nitride sintered body by sintering a molded body of silicon nitride powder blended with a sintering aid such as Y2O3 and a Ce compd. in an inert atmosphere and by successively heat-treating the sintered body in an inert atmosphere and an oxidizing atmosphere. CONSTITUTION:A sintering aid such as Y2O3, Al2O3 or MgAl2O4 and a Ce compd. such as CeO2 are added to silicon nitride powder. This powdery mixture is molded and the molded body is sintered by heating in an inert atmosphere. The sintered body is heat-treated in an inert atmosphere to deposit an apatite phase of oxynitride contg. trivalent Ce at the grain boundary. The heat-treated sintered body is further heat-treated in an oxidizing atmosphere to oxidize the trivalent Ce in the apatite phase to tetravalent Ce. By this oxidation, CeO2 and SiO2 are formed to cause stress deformation and a desired silicon nitride sintered body is obtd. |
