A study was made of diffusion in a solid phase which was in contact with a melt. It was noted that the inter-phase boundary moved, due to dissolution and diffusion of the solid in the melt. A mathematical description involved the solution of the diffusion equation, with constant Dirichlet boundary conditions imposed at the non-stationary boundary of the diffusion field. The problem was solved by using the thermal potential for a double layer. It was found that the values of the diffusion coefficients which were deduced from experimental data by using this theory were higher than those which were estimated in the case where movement of the inter-phase boundary was not taken into account.

P.Kubicek, L.Mrazek: Czechoslovak Journal of Physics, 1996, 46[10], 931-41