Electrical and thermal properties of off-stoichiometric SiC prepared by spark plasma sintering

Off-stoichiometric silicon carbide (SiC), C- and Si-added SiC (6H, α-type), with an excess amount of C or Si from 1 to 5 mol%, were fabricated by spark plasma sintering at 2373 K and 50 MPa in a vacuum. The microstructure, electrical, and thermal properties of off-stoichiometric SiC were investigated. The lattice parameters increased after the addition of C and Si, suggesting the formation of solid solutions of C and Si in SiC. The addition of C and Si increased the densification, while the addition of a small amount of Si (1 mol%) significantly improved the densification. The electrical conductivity (σ) of C-added SiC was 0.7–1.4 × 102 S m−1 at 298–1150 K. The Seebeck coefficient of C-added SiC changed from n- to p-type with increasing addition of C, whereas that of Si-added SiC was almost independent of the amount of Si added. The thermal conductivity of C- and Si-added SiC was in the range of 180–250 W m−1 K−1, which was greater than that of pristine SiC (100 W m−1 K−1) at room temperature.