| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method by which the internal high temp. strength of a silicon nitride sintered compact can be improved while maintaining healing effects on flaws, defects, etc., in the compact. SOLUTION: In this manufacturing method, an aid having a 1 to 3μm average particle size, such as powdery rare earth oxide, Al compound, group 5a element oxide or group 6a element oxide is appropriately added to powdery Si3 N4 having a 0.75μm average particle size and a 95% α ratio to subject them to wet mixing and thereafter, the resulting mixture is dried with a spray dryer to obtain a dry powder. Then, the dry powder thus obtained is subjected to compacting with hydrostatic pressing to form a green compact and thereafter, the green compact is sintered by normal sintering to obtain a sintered compact. Subsequently, first, to obtain the healing effects, the resulting sintered compact is subjected to heat treatment in an oxidizing atmosphere at a comparatively low temp. for 8hr by heating the compact and thereafter, to improve the internal high temp. strength, the treated compact is further subjected to heat treatment in a nitrogen atmosphere at a temp. in the range from liquid phase forming temp. of the aid to the above sintering temp. for 4hr by heating this compact to obtain the objective sintered compact. |
