The measurement of the so-called true grain boundary diffusivity in the C kinetic regime was illustrated for Ag self-diffusion. It was noted that there existed a transitional regime in which classical analysis of grain-boundary diffusion profiles (assuming B-type or C-type conditions) was inapplicable. An alternative method for treating this regime was tested which permitted the determination of both the true grain-boundary double products, and the true grain-boundary diffusion coefficients, from experimental profiles. The ratio of these values furnished the thickness of the grain boundary. This value was consistent with the usually assumed value of 0.5nm. At 423 to 803K, the true grain-boundary diffusivity of Ag could be described by:

D (cm2/s) = 1.26x 10-1 exp[-0.87(eV)/kT]

P.Gas, D.L.Beke, J.Bernardini: Philosophical Magazine Letters, 1992, 65[3], 133-9