Mechanical, thermal, and electrical properties of pressureless sintered SiC–AlN ceramics

Abstract SiC–AlN ceramics were prepared by pressureless sintering and the effects of the polytype of the starting SiC powder and the sintering atmosphere on the mechanical, thermal, and electrical properties of the ceramics were investigated. Almost fully densified SiC–AlN ceramics with a high SiC–AlN solid solution (2Hss) content (75–85%) were fabricated through pressureless sintering using 5 mol% Y2O3 as a sintering additive. Higher flexural strength, hardness, and thermal conductivity of the SiC–AlN ceramic were achieved under nitrogen atmosphere. In contrast, under argon atmosphere, a higher 2Hss content, toughness, and electrical resistivity could be achieved. The use of α-SiC as the starting powder provided higher hardness, electrical resistivity, and thermal conductivity, whereas the use of β-SiC as the starting powder led to higher 2Hss content and toughness. The mechanical, thermal, and electrical properties of the SiC–AlN ceramics prepared by pressureless sintering were significantly affected by the 2Hss content and nitrogen concentration in the liquid phase. The 2Hss content and nitrogen concentration in the liquid phase were influenced by the sintering atmosphere and starting polytype of the SiC powder. Thus, the mechanical, thermal, and electrical properties of the SiC–AlN ceramics could be adjusted, to some extent, through judicious selection of the sintering atmosphere and polytype of the starting SiC powder.