Electrical, thermal and mechanical properties of silicon carbide–silicon nitride composites sintered with yttria and scandia

Abstract

Abstract Composites of SiC–Si 3 N 4 , which consisted of uniformly distributed β-Si 3 N 4 grains, nitrogen-doped β-SiC grains, and a Y- and Sc-containing junction phase, were fabricated by conventional hot-pressing in nitrogen atmosphere, with a new additive system of 2 vol% equimolar Y 2 O 3 –Sc 2 O 3 additives. The effect of Si 3 N 4 content on the electrical, thermal, and mechanical properties of SiC–Si 3 N 4 composites were investigated. The electrical resistivity showed a minimum at 10 vol% Si 3 N 4 content, owing to the growth of nitrogen-doped SiC grains from a Y–Sc–Si oxycarbonitride glass via a solution-reprecipitation mechanism. The thermal conductivity decreased with increasing Si 3 N 4 content, whereas the fracture toughness increased with increasing Si 3 N 4 content. Typical electrical resistivity and thermal conductivity of the SiC–10 vol% Si 3 N 4 composites were 0.09 Ω cm and 83 W/m K at room temperature, respectively. The flexural strength, fracture toughness, and Vickers hardness values of the SiC–35 vol% Si 3 N 4 composite were ∼720 MPa, ∼7 MPa m 1/2 , and ∼19 GPa, respectively.