A new form of diffusion coefficient, the so-called thermodynamic interdiffusion coefficient, was introduced. It was related to the conventional chemical interdiffusion coefficient and to the thermodynamic properties of the system. Three main advantages to using the thermodynamic interdiffusion coefficient were highlighted by applying it to the Al-Ni system. These advantages were a better interpretation of the relative diffusivities in various phases of the same system, the estimation of suitable values of the activation energy for the diffusion process, and the determination of the thermodynamic intrinsic diffusion coefficient (tracer diffusion coefficient) in an intermediate phase with a narrow homogeneity range. The latter was not possible otherwise without performing tracer diffusion experiments.

Thermodynamic Interdiffusion Coefficient in Binary Systems with Intermediate Phases. S.P.Garg, G.B.Kale, R.V.Patil, T.Kundu: Intermetallics, 1999, 7[8], 901-8