Detection of boron segregation to grain boundaries in silicon carbide by spatially resolved electron energy-loss spectroscopy

Boron segregation to grain boundaries in SiC was directly observed for the first time by using spatially resolved electron energy-loss spectroscopy me thods, The hot-pressed, fully dense material was doped with 0.3 wt% of boro n and was free of other additives, except for 2 wt% of free carbon. The det ection of boron was achieved in the difference spectra at all the grain bou ndaries that were examined, Its interfacial excess was in the range of 15-2 9 atoms/nm(2), or approximately one monolayer, Concurrently, silicon deplet ion occurred at these boundaries, although to a lesser extent (-13.5 atoms/ nm(2) on average), which indicated that boron mainly replaces silicon and b onds with carbon at the grain boundary. These findings validate the dual ro le of boron at the grain boundary for promoting densification via improved grain-boundary diffusivity while maintaining a covalent grain boundary with out an oxide phase.