Sintering of silicon nitride to high density

摘要

A silicon nitride compact with a density of 95% to 100% is produced by forming a particulate dispersion of silicon nitride and beryllium additive into a compact, firstly sintering the compact from about 1900 DEG C. to about 2200 DEG C. in nitrogen at superatmospheric pressure sufficient to prevent thermal decomposition of the silicon nitride until the entire outside surface of the compact becomes impermeable to nitrogen gas, and then secondly sintering the compact from about 1800 DEG C. to about 2200 DEG C. under a nitrogen pressure having a value at least twice the first nitrogen sintering pressure.