The grain boundary diffusion of Te in Ag was studied over a temperature range of about 600K by using 121Te and 123Te radio-tracers. It was found that, at temperatures of between 378 and 504K, a type-C Harrison regime existed; which permitted direct measurements to be made of the grain-boundary diffusion coefficient (tables 13 and 14). The activation energy and pre-exponential factor for the latter diffusivity were equal to 86.75kJ/mol and 0.000101m2/s. This was the first study which had involved C-regime measurements of impurity grain-boundary diffusion, and accurate estimates of the grain boundary segregation factor from the associated diffusion data. Upon comparing the present results with previous C-regime measurements of grain boundary self-diffusion in Ag, it was concluded that there was a possibility of 2-dimensional phase formation during Te grain-boundary diffusion in Ag.

C.Herzig, J.Geise, J.Mishin: Acta Metallurgica et Materialia, 1993, 41[6], 1683-91

Table 13

Grain Boundary Diffusivity of 121Te in Ag