Conductive SiC ceramics fabricated by spark plasma sintering

Abstract

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 0.05wt%) contained a graphitic phase (1580 and 2710cm−1) which was insignificant for high Y2O3 content (1.0 and 5.0wt%). 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 10−2Ωcm but exhibited photoluminescence spectra quite different from each other. The p-type character is primarily attributable to silicon vacancies (VSi), while the n-type character is ascribed to nitrogen substitution in carbon sites (NC) 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 VSi and NC.