Densification, microstructure and properties of liquid-phase sintered silicon carbide

Liquid-Phase Sintered Silicon Carbide (LPSSiC) materials were produced with different Y203:Al203 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 Y203:Al203 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. Microstructures 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.