Occurrence and Distribution of Boron‐Conitaining Phases in Sintered ş‐Silicon Carbide

A variety of optical and analytical instruments have been employed to observe and characterize the mlcrostructure and composition of the B‐containing phases which occur in sintered α‐SiC as a result of either their use as a nensification aid or that which evolves as a result of annealing well below the sintering temperatures. The former have been identified as B₄C containing a small amount of Si. The latirr occur as ∼20‐nm precipitates which have also been tentatively identified as B₄C and are believed to contain trace quantities of Si. No B phase was observed on the SiC grain boundaries; furthermore, the precipitate formation was not enhanced by the application of stress.