| 摘要 |
SILICON NITRIDE SINTERED BODY AND PROCESS FOR PREPARATION THEREOF A silicon nitride sintered body comprised of 1.5 to 3.0% by weight of Y2O3 , 0.1 to 1.0% by weight of Al2O3 and 96 to 98.4% by weight of Si3N4 wherein the Y2O3/Al2O3 weight ratio is at least 2.5, and having a density of at least 3.0 g/cm3, exhibits a high oxidation resistance and a high strength at a high temperature. This silicon nitride sintered body is prepared by sintering a powdery mixture consisting essentially of 1.5 to 3.0% by weight of Y2O3 powder, 0.1 to 1.0% by weight of Al2O3 powder, and 96 to 98.4% by weight of Si3N4 powder, the Y2O3/Al2O3 weight ratio being at least 2.5, the oxygen content in the Si3N4 powder being less than 2.0% by weight and the total metallic impurity content in the Si3N4 being less than 200 ppm, at a temperature of 1,850 to 2,000.degree.C in a non-oxidizing atmosphere. |
