Sintering shrinkage behavior of Si_3N_4 ceramics prepared by a post-reaction sintering technique

摘要

Post-reaction sintering is one of the fabrication processes of Si_3N_4 ceramics, which has received considerable attention as a cost-effective process due to the use inexpensive Si powder as a raw material. So far, many researches on the development of this method have been performed in order to improve their properties; however, the sintering shrinkage behavior, which is valuable for the optimization of the firing conditions, has not been well clarified. In this study, we focus on the post-reaction sintering of the Si-Y_2O_3-Al_2O_3 system, and investigate its sintering shrinkage behavior by dilatometery. It was found that there is no shrinkage from 1400 to 1600 ℃ due to grain rearrangements in the green body of the reaction-bonded Si_3N_4. Furthermore, the shrinkage of the reaction-bonded Si_3N_4 commenced at approximately 1750℃, which is higher than the shrinkage temperature of the green body of conventional Si_3N_4 powder. The restriction of the shrinkage appears to result from the neck growth and strong aggregation among the reacted Si_3N_4 particles.