| 摘要 |
PURPOSE:To obtain a silicon nitride sintered compact which has high breaking toughness and is adequate as a high-temp. structural material, etc., by composing this sintered compact of a main phase consisting of a beta-silicon nitride crystal and a grain boundary phase contg. specific different particle materials, pores and a sintering assistant. CONSTITUTION:(A) alpha-silicon nitride powder which is an essential component, (B) 1 to 20vol.% different particle powder selected from silicon carbide, titanium boride, titanium carbide, titanium nitride and zirconium boride having a coefft. of thermal expansion larger than the coefft. of thermal expansion of the silicon nitride and a grain size 0.1 to 10mum, (C) 1 to 10mol% yttrium oxide powder and (D) 1 to 10mol% total of one or <=4 kinds selected from aluminum oxide, neodymium oxide, lanthanum oxide and cerium oxide are mixed. This power raw material mixture is then sintered in a nitrogen atmosphere. As a result, the sintered compact consisting of the grain bounding phase having the main phase consisting of the beta-silicon nitride crystal, contg. 1 to 20vol.% component B, contg. pares having a diameter up to 30mum up at max. 11vol.% and contg. a sintering assistant for the balance is obtd. |
