Interdiffusion experiments, performed above and below the critical temperature for de-mixing, were carried out on quasi-binary systems with a spinodal miscibility gap. The effect of thermodynamics upon the Arrhenius parameters for interdiffusion was determined as a function of the excess Gibbs energy. This could be calculated if the thermodynamic interaction parameters of the system were known. The interdiffusion coefficient comprised a mobility term and a thermodynamic factor. Assuming that the logarithm of the mobility term depended linearly upon composition, the evolution of the thermodynamic factor was extracted from experimental diffusion data and was compared with the predictions of a theoretical model. It was shown that, in systems which exhibited a marked deviation from ideal behavior, the interdiffusion exhibited a minimum at the critical de-mixing composition. The Arrhenius parameters, as a function of composition, exhibited maxima that tended to infinity when a critical point was approached. The so-called correlation effect, in the composition dependence of the Arrhenius parameters for interdiffusion, could be understood qualitatively in systems that exhibited a distinct deviation from ideal behavior.

The Influence of Thermodynamics on the Interdiffusion in Quasibinary Systems. V.Leute: Solid State Ionics, 2003, 164[3-4], 159-68