PURPOSE: To obtain fine α-type silicon nitride powder of high purity suitable for use in the manufacture of a high stress material for high temp. use by rapidly heating a silane compound contg. nitrogen, and thermally decomposing and crystallizing it to manufacture silicon nitride.
CONSTITUTION: A silane compound contg. nitrogen such as silicon diimide obtd. by reacting silicon halide with ammonia is thermally decomposed and crystallized. At this time, the compound is heated while controlling the temp. rising speed in the temp. range of 1,350W1,550°C to ≥15°C/min, and it is held at about 1,550W1,700°C to manufacture silicon nitride by thermal decomposition. Thus, the resulting silicon nitride is inhibited from being made larger in grain size, the formation of β-type silicon nitride is prevented, and fine polycrystalline α-type silicon nitride powder is obtd. A sintered body obtd. by sintering this silicon nitride powder is chemically and physically stable and shows high strength.
KASAI KIYOSHI
TSUKIDATE TAKAAKI
