The impurity diffusion of Se in polycrystals was investigated by using 75Se radiotracer and serial sectioning techniques over a temperature range of 600K. In the type-C regime, the grain boundaries diffusivities were measured directly and could be described by:

D(cm2/s) = 2.6 x 10-3exp[-13.2(kcal/mol)/RT]

T.Surholt, J.M.Mishin, C.Herzig: Solid State Phenomena, 1995, 41, 113-20