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

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 10 vol%, 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-10 vol% BN composite were 9.3 × 105 Ω × cm, 74.4 W/m K, 559 MPa, 3.6 MPa m1/2, and 23 GPa, respectively.