By using hot isostatically-pressed B-doped material, it was demonstrated that the structural width and chemical width of a general boundary could be quite different. High-resolution electron microscopic observations did not detect the existence of an approximately 1nm-thick amorphous film at such grain boundaries. There was a core structure of only 1 or 2 atomic planes at the grain boundary. The chemical width of the grain boundary, as deduced from a spatially-resolved electron energy-loss spectroscopic analysis, was visibly wider than the core region. Spatially-resolved energy-loss near-edge structural analysis not only revealed the chemical bonding between B and C, O and Si, but also revealed an extended grain boundary region in which the chemical bonding was modified in comparison to that of grain interiors. Such analysis revealed a width that was even wider than the chemical width. These 3 grain-boundary widths, of differing scale, suggested a comprehensive picture for general boundaries that was markedly different from general boundaries with an amorphous film. Instead of a film which was confined by the 2 atomically sharp grain surfaces, there was now only one interface. The rough grain boundary core contained most of the B-C and Si-O bonds, and an extended grain surface layer formed the general grain boundary in B-doped SiC.

Structural and Chemical Widths of General Grain Boundaries: Modification of Local Structure and Bonding by Boron-Doping in β-Silicon Carbide. H.Gu, Y.Shinoda: Interface Science, 2000, 8[2-3], 269-78