Effect of α-Si_3N_4 powder bedding on the microstructure of gas pressure sintered Si_3N_4 ceramics

摘要

The effect of α-Si_3N_4 powder bedding on the densification behavior and microstructure was investigated. The microstructure was strongly dependent on the bedding condition. The specimens sintered with α-Si_3N_4 powder bedding consisted of relatively small garins as compared to those of specimens sintered without bedding. It is believed that the grain growth of specimens sintered without bedding occurred earlier than that of specimens sintered with α-Si_3N_4 powder bedding because of the rapid densification and α-to-β phase transformation. Consequently, the microstructure of the specimen sintered without bedding consisted of larger grains.