Silicon nitride sintered body and process for preparing the same.

摘要

A silicon nitride sintered body containing silicon nitride and/or sialon in an amount of at least 85% by weight and having a relative density of at least 98%, wherein the silicon nitride and/or sialon consists of particles whose greatest diameters measured on a two-dimensional section of the sintered body are each less than 5 mu m, and silicon nitride and/or sialon particles whose greatest diameters mentioned above are each 0.7 mu m or less account for 40 to 70% of the total cross sectional area of all the particles. Fine particles of compound(s) mainly composed of nitride(s) of element(s) of Group 4A, each having a size of 500 nm or less may be dispersed in the above sintered body of silicon nitride. The silicon nitride sintered body is produced by mixing a specific material powders, molding the mixture, subjecting the molded body to primary and secondary sinterings under the specific conditions so as to attain a relative density of at least 98% in the resultant sintered body. <IMAGE>