| 摘要 |
PROBLEM TO BE SOLVED: To produce a thin or thick silicon nitride sintered compact preventing oxidation at low temp. while maintaining high strength at high temp. and capable of exhibiting strength even at low temp. SOLUTION: In this silicon nitride sintered compact contg. silicon nitride and compds. of rare earth elements, Yb and Y are contained as the rare earth elements by 5-7mol% in total (expressed in terms of oxides) in a molar ratio of 4:6 to 9:1 (expressed in terms of oxides), H and J phases are contained as crystals phases at the grain boundaries and the percentage of the H phase is higher than that of the J phase. This sintered compact is produced by adding Yb2 O3 and Y2 O3 as sintering aids to Si3 N4 powder by 5-7mol% in total in a molar ratio of 4:6 to 9:1, mixing and compacting them, sintering the resultant compact at 1,850-1,950 deg.C in an atmosphere of nitrogen and carrying out heat treatment at 1,000-1,500 deg.C for 0.5-10hr in the air. |
