| 摘要 |
PURPOSE:To obtain a silicon nitride sintered body which is improved in strength and fracture toughness by sintering Si3N4 powder which contains a specific ratio of Ca and is not added with a sintering assistant. CONSTITUTION:This silicon nitride sintered body is obtd. by sintering the silicon nitride powder which contains, by weight, 100-1,000ppm calcium and is not added with the sintering assistant. The Si3N4 powder which contains the Ca at a low ratio and is obtd. by a direct reaction method, imide thermal decomposition method, SiO2 reduction method, etc., is used. The other impurities in the Si3N4 powder, for example, metal impurities such as Fe, Al, Mn and Ni and impurities such as C and Cl may be incorporated therein within the range where the properties are not degraded. The lower ratios thereof are more preferable. The Ca is preferably added to the Si3N4 powder in the form of, for example, oxide CaO. This silicon nitride sintered body is not added with the assistants as an auxiliary effect, unlike with the conventional sintered bodies, and therefore, the oxidation of the sintered body by the exudation of such assistants on the surface is obviated and the oxidation resistance is improved. |
