The grain boundary solute diffusion of Se in Ag polycrystals was investigated systematically by using serial sectioning technique and the 75Se isotope at 371 to 877K. The measurements were performed in the Harrison type-B regime at high temperatures and in the type-C regime at low temperatures. The solid solubility of Se was very small, and Se formed an intermetallic compound; indicating the predominance of Se-Ag bonds. The measured grain-boundary diffusivity of Se was close to that for grain-boundary self-diffusion, but the activation enthalpy was higher for Se grain-boundary diffusion than for Ag grain-boundary diffusion. This was explained in terms of the formation of embryos of 2-dimensional phases at high-energy grain-boundary sites. The results could be described by:

sδD (m3/s) = 3.0 x 10-14 exp[-63.5(kJ/mol)/RT]

D (m2/s) = 4.1 x 10-4 exp[-84.8(kJ/mol)/RT]

T.Surholt, C.Minkwitz, C.Herzig: Acta Materialia, 1998, 46[6], 1849-59