| 摘要 |
PURPOSE:To enhance deflection strength and toughness by constituting the sintered body of Si3N4, oxide of rare earth elements and (excess O2/oxide of rare earth elements) which have a specified molar ratio and incorporating fine Fe powder at a low content in the sintered body. CONSTITUTION:Si3N4 powder having 3-20m<2>/g BET specific surface area, >=95% alpha-rate of change and 0.8-1.4wt.% O2 content is washed by acid such as hydrochloric acid. This treated treated Si3N4, rare earth elements and SiO2 are weighted at prescribed amount and mixed. Thereafter a binder is added and the mixture is granulated and molded. Then the molded body is heated to remove the binder thereafter calcined at 1200-1600 deg.C in an inert gas atmosphere. Furthermore powder such as BN powder which is bad in wetting to glass is applied to the surface of the molded body at about 1-10mm. Then the impurities in BN powder are removed by heat-treating the molded body at 1200-1450 deg.C at a reduced pressure. Thereafter glass powder is applied to the surface and the molded body is roasted at 1450-1800 deg.C in the gaseous N2 atmosphere by an HIP method. An Si3N4-based sintered body is obtained which incorporates 70-99mol% (hereinafter shown in %) Si3N4, 0.1-5% oxide of rare earth elements, <=25% excess O2 (expressed in terms of SiO2), 2-55 molar ratio (excess O2/oxide of rare earth elements) and <=50ppm Fe content and has <=7mum mean particle diameter. |
