The effect of sintering temperature on the mechanical and thermal properties of SiC ceramics sintered with Al2O3-Y2O3-CaO without applied pressure was investigated. SiC ceramics containing A(2)O(3)-Y2O3-CaO as sintering additives can be sintered to >97% theoretical density at temperatures between 1750 degrees C and 1900 degrees C without applied pressure. A toughened microstructure, consisting of relatively large elongated grains and relatively small equiaxed grains, has been obtained when sintered at temperatures as low as 1800 degrees C for 2 h in an argon atmosphere without applied pressure. The achievement of toughened microstructures under such mild conditions is the result of the additive composition. The thermal conductivity of the SiC ceramics increased with increasing sintering temperature because of the decrease in the lattice oxygen content of the SiC grains. Typical sintered density, flexural strength, fracture toughness, hardness, and thermal conductivity of the 1850 degrees C-sintered SiC, which consisted of 62.2% 4H, 35.7% 6H, and 2.1% 3C, were 99.0%, 628 MPa, 5.3 MPam(1/2), 29.1 GPa, and 80 W(mK)(-1), respectively.