Microstructure and mechanical properties of alpha-silicon carbide sinteredwith yttrium-aluminum garnet and silica

The effect of glassy-phase chemistry, using Y3Al5O12 (YAG) and SiO2 as sint ering additives, on the microstructure and mechanical properties of liquid- phase-sintered, and subsequently annealed, alpha-SiC materials was investig ated. The microstructural development of annealed materials was insensitive to changes in glass chemistry. The mechanical properties vs SiO2/YAG ratio curve had a maximum; i.e., there was a small glass composition range at wh ich optimum mechanical properties were realized, The best results were obta ined when the ratio was similar to 0.5. The flexural strength and fracture toughness of the material were >450 MPa and >6 MPa.m(1/2), respectively.