Sintering behavior of several kinds of Si_3N_4 powders with different content of alpha-phase using Y_2O_3 and MgO as sintering aids

摘要

In this study, several kinds of Si_3N_4 powders with different content of alpha-phase were used as raw materials, and Y_2O_3 and MgO powders were added as sintering aids. The relative density of the Si_3N_4 ceramics from the powder with higher alpha content was lower than that with lower alpha content under all of the sintering temperatures and soaking times. It seems that densification was inhibited by abnormal growth of elongated beta-Si_3N_4 grains, which occured in only the sample fabricated from the Si_3N_4 powder with higher alpha content, because Y_2O_3 and MgO as sintering aids enhanced grain growth at lower temperature in spite of less nucleation due to low viscosity and wettability of liquid phase.