Influence of Y_2O_3 addition on electrical properties of β-SiC ceramics sintered in nitrogen atmosphere

摘要

The influence of Y_2O_3 addition on electrical properties of (3-SiC ceramics has been investigated. Polycrystalline SiC samples obtained by hot-pressing SiC-Y_2O_3 powder mixtures in nitrogen (N) atmosphere contain Y_2O_3 clusters segregated between SiC grains. Y_2O_3 forms a Y-Si-oxycarbonitride phase during sintering by reacting with SiO_2 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) Q cm and a carrier density of ~ 10~(20) cm~(-3), which are ascribed to donor states derived from N impurities. The increase in defect density with increasing Y_2O_3 content is likely to be a main limiting factor of the electrical conductivity of SiC ceramics.