Electrically conductive SiC-BN composites

SiC-BN composites were fabricated by conventional hot-pressing from β-SiC and h-BN powders with 2 vol% Y2O3 as a sintering additive. Electrical, mechanical, and thermal properties of SiC-BN composites were investigated as a function of the BN content in the starting materials. The addition of BN suppressed the grain growth of the SiC and triggered the β → α phase transformation of the SiC in SiC-BN composites. A minimum electrical resistivity of 3.7 × 10−2 Ω cm was obtained for the SiC-4 vol% BN composite (SBN4). This low electrical resistivity was ascribed to N-doping in the SiC lattice, which acts as a donor for supplying electrons to the conduction band. Typical values for the electrical conductivity, fracture toughness, flexural strength, and thermal conductivity of the SBN4 at room temperature were 27 Ω−1 cm−1, 4.1 MPa m1/2, 566 MPa, and 87 W/m K, respectively. The SiC-4 vol% BN composite can be electrical discharge machined to form complex shapes.