| 摘要 |
PURPOSE: To obtain silicon nitride ceramics excellent in strength at high temp. by adding a sintering aid made of multiple oxides of specified rare earth elements to silicon nitride stock and sintering them in a nitrogen atmosphere after compacting. CONSTITUTION: Oxides of two or more kinds of rare earth elements such as Sc, Y, Tb and Dy are mixed, pulverized and calcined at 1,0001,750 deg.C to form multiple oxides of the rare earth elements. About 0.5-10wt.% powder of this multiple oxide is added as a sintering aid to silicon nitride stock and they are sintered in a nitrogen atmosphere to produce the objective silicon nitride ceramics. The compsn. of a formed glass phase and the thickness of a formed grain boundary phase are made uniform and the strength of the ceramic at high temp. can be enhanced. The ceramics are useful as an engine member, etc., requiring strength at high temp. |
