Abstract

A new analytical method for computing concentration-dependent interdiffusion coefficients, when a non-uniform solute distribution pre-exists in a substrate prior to diffusion in a binary system, is developed from Fick’s laws of diffusion. The key concept of the new method is validated by experimental data reported in the literature. This new method addresses the limitations of previous analytical techniques such as Boltzmann–Matano, Saucer–Friese, and Sarafianos methods, which are restricted to a single solute concentration profile, with no non-uniform initial solute distribution. The analyses of numerically simulated concentration profiles show that previous standard analytical methods are erroneous when computing the interdiffusion coefficients in binary systems with significant non-uniform initial solute distributions. In contrast, the new analytical method can reliably compute the concentration-dependent interdiffusion coefficient operative between two isothermal concentration profiles obtained at different diffusion times. Practically, this method can be used to extract concentration-dependent interdiffusion coefficients from planar diffusion systems with non-uniform initial solute distribution caused by pre-diffusion or multi-staged diffusion processes.

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