Influence of Y2O3 addition on electrical properties of β-SiC ceramics sintered in nitrogen atmosphere

The influence of Y2O3 addition on electrical properties of β-SiC ceramics has been investigated. Polycrystalline SiC samples obtained by hot-pressing SiC–Y2O3 powder mixtures in nitrogen (N) atmosphere contain Y2O3 clusters segregated between SiC grains. Y2O3 forms a Y–Si-oxycarbonitride phase during sintering by reacting with SiO2 and SiC and by dissolution of N from the atmosphere; this induces N doping into the SiC grains during the process of grain growth. The SiC samples exhibit an electrical resistivity of ∼10−3 Ω cm and a carrier density of ∼1020 cm−3, which are ascribed to donor states derived from N impurities. The increase in defect density with increasing Y2O3 content is likely to be a main limiting factor of the electrical conductivity of SiC ceramics.