Thermal, electrical, and mechanical properties of pressureless sintered silicon carbide ceramics with yttria-scandia-aluminum nitride

The effects of the polytype of SiC starting powders on the thermal, electrical, and mechanical properties of pressureless sintered SiC ceramics with a new additive system (6.5 vol% Y2O3-Sc2O3-AlN) were investigated. Powder mixtures prepared from α- or β-SiC powders were sintered at 1950 °C for 6 h in a nitrogen atmosphere without an applied pressure. We found that both specimens could be sintered to >96% of the theoretical density without an applied pressure. The SiC ceramic fabricated from β-SiC powders showed lower electrical resistivity, higher thermal conductivity, and better mechanical properties than that from α-SiC powders. The flexural strength, fracture toughness, hardness, electrical resistivity and thermal conductivity values of the SiC ceramics fabricated from β-SiC powders were 520 MPa, 5.1 MPa m1/2, 25.0 GPa, 6.7 × 10−1 Ω cm and 110 Wm−1 K−1 at room temperature, respectively. The new additive system achieved the highest thermal conductivity in pressureless liquid-phase sintered SiC ceramics.