Grain boundary structures in silicon carbide: Verification of the extended boundary concept

A grain boundary layer of ca. 0.5 nm in thickness is present in B+C added SiC and SiC without any sintering aids. Since these materials do not show a significant strength-decrease at high temperatures, Ikuhara et al. presumed that the layer is not a second phase of sintering aids or impurities but a reconstructed structure formed to reduce the high energy of the grain boundary, and they called such a boundary an extended boundary. The concept of the extended boundary, however, has not yet been generally accepted for lack of convincing evidence. In the present work, the elements analysis of the boundary layer was made and some additional collateral verifications were conducted in order to inspect the extended boundary concept.