It was noted that the exchange of a radioactive tracer between the 2 samples which formed a diffusion couple depended upon the diffusion rate of the tracer in each sample and also upon the transfer rate of the tracer across the interface between the samples. The interface could also contain a barrier layer having a different chemical composition and/or structure. Diffusion couples having 3 different initial tracer distributions were considered here. A detailed analysis was made of the mathematics which were required in order to extract values of the tracer diffusion coefficients, and of the rate constant for transport across the interface, from experimental data. This analysis was also of interest for obtaining true values of the bulk diffusivities and for the quantitative characterization of the resistance of interfaces to the exchange of certain species.

Bulk Diffusion Measurements to Study the Effectiveness of Barrier Layers - I. Mathematical Treatment. L.Tian, M.O.Thompson, R.Dieckmann, C.Y.Hui, Y.Y.Lin: Journal of Applied Physics, 2001, 90[8], 3799-809