Gorsky-effect relaxation measurements were used to study diffusion in 4N84-purity recrystallized material (table 82). The diffusion coefficients were very large, and exhibited only a weak exponential temperature dependence (which decreased, below 300K, for H). Contrary to classical rate theory, the activation energies were isotope-dependent whereas the pre-exponential factors were isotope-independent to within experimental error.

G.Schaumann, J.Völkl, G.Alefeld: Physica Status Solidi, 1970, 42[1], 401-13

Table 78

Grain Boundary Diffusivity of Cu in [1¯01]/[112] Nb Bicrystals

as a Function of Temperature and Tilt Angle