The orientation phase-space averaged excess volume that was associated with grain boundaries in nanocrystalline material was deduced from a rule-of-mixtures analysis of density and thermal expansion coefficient measurements. The atomic density was found to fluctuate along the grain-boundary core with an amplitude that could be reduced by low-temperature annealing. The scaling relationship between resistivity and crystallite size changed significantly below about 7nm. It was suggested that, in this limit, the intrinsic nature of a grain boundary became linked to its spatial extent.

R.Birringer, C.E.Krill, M.Klingel: Philosophical Magazine Letters, 1995, 72[2], 71-7