Conductive SiC ceramics fabricated by spark plasma sintering

Bulk SiC ceramics were fabricated by spark plasma sintering, and the effects of Y₂O₃ addition on the structural and electrical properties were investigated. Raman spectroscopy revealed that SiC specimens with low Y₂O₃ content (0.01 and 0.05 wt%) contained a graphitic phase (1580 and 2710 cm⁻¹) which was insignificant for high Y₂O₃ content (1.0 and 5.0 wt%). Carbon-rich SiC specimens exhibited p-type conduction character, while others exhibited n-type character. The p- and n-type SiC specimens had electrical resistivities around 10⁻² Ω cm but exhibited photoluminescence spectra quite different from each other. The p-type character is primarily attributable to silicon vacancies (V_Si), while the n-type character is ascribed to nitrogen substitution in carbon sites (N_C) of the zincblende lattice. The change in conduction type with yttria addition in the SiC specimen can be understood in terms of a competition between the densities of V_Si and N_C.