Analytical electron microscopy of graphite-rich inclusions in sintered α-silicon carbide

Intragranular inclusions and multiphase regions at triple grain junctions in (B+C)-doped sintered α-SiC were investigated using analytical and high-resolution electron microscopy. Both regions were two-phase, composed of graphite and amorphous material. The triple junctions also contained pores. The amorphous regions were principally carbon and oxygen. Graphite was formed by partial transformation of the amorphous regions. Only the triple-junction regions contain typical impurities from the starting α-SiC powder, inferring that they are the main sinks for all grain-boundary/surface impurities in the material system.