PURPOSE: To obtain a sintered compact having high strength and high realizbility by sintering powdery silicon nitride having a prescribed β phase content and a prescribed amount of amorphous component.
CONSTITUTION: Powdery silicon nitride is produced by a method of direct nitriding of metallic silicon, a silica reduction method, a silicon halide method, etc., e.g. in the silicon halide method silicon tetrachloride and ammonia are reacted at a low temperature and produced silicon diimide is thermally decomposed to obtain amorphous silicon nitride, to which 10-30wt.% powdery β silicon nitride is added and heated to crystallize at 1300-1400°C in a nitrogen atmosphere. Thus, e.g. 93 pts.wt. powdery silicon nitride having ≥50% β phase content, 5-50wt.% amorphous component and ≥2m2/g specific surface, 5 pts.wt. Y2O3 powder having 1.5μm average size and 2 pts.wt. Al2O3 powder having 0.8μm average size are wet mixed in 1,1,1-trichloroethane in a ball mill for 4 hours and dried, formed under ca.100kg/cm2 pressure, then formed by CIP (cold isostatic press) at 700kg/cm2 and sintered.
ISOZAKI HIROSHI
SHIMODAIRA HIROSHI
NISHIKAWA HIROSHI
KAGA TETSUO
