Electrical and thermal properties of silicon carbide–boron nitride composites prepared without sintering additives

Abstract

Composites of SiC–BN consisting of uniformly distributed plate-shaped hexagonal BN grains and nitrogen-doped α-SiC grains were fabricated by conventional hot-pressing in an argon atmosphere without sintering additives. The effects of the BN content on the electrical, structural, thermal, and mechanical properties of the SiC–BN composites were investigated. The electrical resistivity showed a minimum at a BN content of 10vol%, which is attributable to N substitution for C sites in the 6H–SiC lattice, which acts as donors for supplying carriers to the conduction band. The thermal conductivity of the composites showed a decreasing trend with increasing BN content, indicating that the presence of the SiC/BN interface discourages phonon conduction in the composites. The electrical resistivity, thermal conductivity, flexural strength, fracture toughness, and hardness of the SiC–10vol% BN composite were 9.3×105Ω×cm, 74.4W/mK, 559MPa, 3.6MPam1/2, and 23GPa, respectively.