Ss-sic-powders sinter and process for its manufacture

A beta -SiC powder suitable as a sintering material is prepared by mixing a silica powder of high purity not larger than 50 mu m in particle size and a carbon powder not larger than 1 mu m in particle size and not more than 0.2 wt% in ash content such that the C/SiO2 ratio falls in the range from 2.8 to 4.0, and firing the mixture in a nonoxidizing atmosphere at a temperature lower than 2000 DEG C and not lower than 1700 DEG C for not more than 2 hr. The beta -SiC powder contains less than 5 wt% and not less than 1 wt% of 2H??? phase and is not larger than 1 mu m in mean particle size and is in the range from 12 to 20 m /g in specific surface area measured by the BET adsorption method. Preferably the particle size distribution of the beta -SiC powder is controlled so as to contain fairly fine particles, relatively coarse particles and intermediate particles in adequate proportions. A sintered body of beta -SiC having good microstructure and high mechanical strength is easily obtained by sintering a green body formed on this beta -SiC powder in a nonoxidizing atmosphere at 1900-2100 DEG C.