| 摘要 |
PURPOSE:To obtain the subject sintered material having excellent high- temperature strength and improved oxidation resistance from a low temperature to a high temperature. CONSTITUTION:A mixture composed of silicon nitride, an S oxide of a group 3a element of the periodic table (RE2O3) and silicon oxide (SiO2) at an SiO2/RE2 O3 molar ratio of >=2 is formed, sintered, temporarily maintained at a temperature between the softening temperature Tg of the glass formed on the grain boundary of the sintered material and the crystallization temperature Tc of silicon nitride to RE2Si2O7 to generate crystal nuclei of RE2Si2O7. The product is heat-treated by maintaining at a temperature between Tc and a eutectic point Te of silicon nitride crystal and RE2Si2O7 crystal to effect the growth of the crystal nuclei of RE2Si2O7. The formation of RE2Si2O7 crystal in the grain boundary is promoted and the average thickness (t) of the amorphous layer 4 between the silicon nitride crystal particle 1 and the RE2Si2O7 crystal 3 at the triple point of the grain boundary 2 is controlled to <=5nm. |
