Densification, Microstructure and Properties of Liquid-Phase Sintered Silicon Carbide

摘要

Liquid-Phase Sintered Silicon Carbide (LPSSiC) materials were produced with different Y_2O_3:Al_2O_3 sintering additive ratios. Different densification techniques were employed (hot pressing (HP) and gas pressure sintering (GPS)) and densification kinetics studied. The results show significant increase in densification with decreasing Y_2O_3: Al_2O_3 ratio. Microstructure and phase evolution during sintering and post-sintering heat treatment was studied. The ratio of the SiC polytypes and the amount and crystalline composition of grain boundary phases was determined using Rietveld analysis. Micro structures of the materials were related to mechanical (hardness, fracture toughness and strength) and electrical properties. Electrical properties were studied using Impedance Spectroscopy. By this method, the resistivities of the grain and grain boundaries could be separated.