添加稀土氧化物热压氮化硅陶瓷的蠕变机制

Creep Mechanisms of Hot-Pressed Silicon Nitride Ceramics with Rare-Earth Oxide Additives

The creep mechanisms of hot-pressed silicon nitride ceramics with rare-earthoxide additives without and with extra alumina in various amounts have been stu-died.Based on the stress exponent derived from the experimental result and micro-structure observation a compound mechanism of creep,or diffusional viscous flowas the controlling factor,and grain boundary sliding together with cavity forma-tion as the concurrent mechanism,is suggested for HPSN with rare-earth additives,while the grain boundary separation caused by cavitation is responsible to the HPSNwith rare-earth additives furthermore with extra alumina.LaYO_3 crystalline phasecan be separated out from the glassy phase of grain boundaries by heat treatment,and thus the stress exponent of the material drops,while the diffusional mechanismpredominates.