| 摘要 |
PROBLEM TO BE SOLVED: To obtain a dense high strength sintered compact by a single gas pressure sintering process without requiring a large-scale apparatus by firing a green compact consisting of a powdery starting material for Si3 N4 , Yb2 O3 powder, a powdery Mg compd. and a powdery Al compd. in two stages under specified conditions in an inert atmosphere. SOLUTION: The green compact is preferably fired in two stages in the inert atmosphere. In the 1st stage, the green compact is heated in the atmosphere under 1-2 atm pressure and held at 1,400-1,600 deg.C preferably for 0.5-2 hr until it is made substantially free from open pores. In the 2nd stage, the pressure of the atmosphere is increased to >=30 atm and the green compact is held at 1,400-1,600 deg.C preferably for 2-5 hr until the residual α-rate of the resultant sintered compact attains to 5-35%. The sintered compact contains 4-10 wt.% (expressed in terms of Yb2 O3 ) Yb, 2-5 wt.% (expressed in terms of MgO) Mg and 0.5-4 wt.% (expressed in terms of Al2 O3 ) Al and the weight ratio of Al2 O3 to MgO is <=1. |
