| 摘要 |
PURPOSE:To obtain the sintered products of high oxidation resistance and high strength at elevated temperature, by calcining a mixed powder in which a proportion of lanthanum oxide, aluminum oxide and silicon nitride, the oxygen content and the total amount of metal impurities are specified at a specific temperature and pressure. CONSTITUTION:The proportion of powders of lanthanum oxide, aluminum oxide and silicon nitride is specified to 1.0-2.5wt.% of lanthanum oxide, 0.1-2.5wt.% of aluminum oxide where the weight ratio of the lanthanum oxide/aluminum oxide is over 0.6, and the rest part of silicon nitride. The oxygen content in the silicon nitride is less than 2.0wt.% and the total amount of the metal impurities is less than 200ppm. The powder mixture is sintered in a nitrogen atmosphere at 1,900-2,100 deg.C under pressure over 5kg/cm<2>G. The sintering temperature must be 1,900-2,100 deg.C and lower temperature results in unsatisfactory densification of the sintered products, while too high temperature causes undesirably the decomposition of silicon nitride. |
