Effects of adding methods of YAG on sintering behaviour,mechanical properties and microstructure of SiC ceramic

SiC composite powders were respectively synthesized by sol-gel method and mechanical mixing method, and were pressureless liquid-phase sintered to prepare silicon carbide ceramic. The effects of adding methods on the sintering behaviour, mechanical properties and microstructure of silicon carbide ceramic were analyzed. The results show that at the sintering temperature of 1950℃, silicon carbide ceramic, with SiC/(Al_2O_3+Y_2O_3) composite powder by mechanical mixing method, possesses higher sintering properties, higher mechanical properties and more ideal microstructure than those with SiC/YAG composite powder by sol-gel method, and there exists over-sintering phenomenon in the SiC/YAG composite powder. After optimizing the process, silicon carbide ceramic, sintered at (1860℃) with SiC/YAG composite powder by sol-gel method, can obtain excellent sintering and mechanical properties and perfect microstructure. Formation ahead of sintering and uniform distribution of YAG phase in composite powder can accelerate the densification, decrease sintering temperature and improve mechanical properties and microstructure of silicon carbide ceramic. The fine grains, crack deflexion and grain-bridging are main toughening mechanisms of silicon carbide ceramic.