Simultaneous measurement of tracer and interdiffusion coefficients: an isotopic phenomenological diffusion formalism for the binary alloy

• Published in: Philosophical magazine (Abingdon, England) England), 2013-09, Vol.93 (26), p.3515-3526
• Main Authors: Belova, I.V., Kulkarni, N.S., Sohn, Y.H., Murch, G.E.
• Format: Article
• Language: English
• Subjects: Binary alloys; Condensed matter: structure, mechanical and thermal properties; Diffusion; Diffusion in solids; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fluxes; Formalism; Interdiffusion; isotope; Law; Onsager; phenomenological; Physics; SIMS; Solubility, segregation, and mixing; phase separation; theoretical; tracer; Tracer diffusion; Transport properties of condensed matter (nonelectronic)
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786435.2013.813982

In this paper, a new development of the classic Onsager phenomenological formalism is derived using relations based on linear response theory. The development concerns the correct description of the fluxes of the atomic isotopes. The resulting expressions in the laboratory frame are surprisingly simple and consist of terms coming from the standard interdiffusion expressions and from Fick's first law, where the tracer diffusion coefficient is involved thus providing a better understanding of the relationship between the two approaches - Fick's first law and the Onsager phenomenological formalism. From an experimental application perspective, the new development is applied to the binary alloy case. The formalism provides the means to obtain the interdiffusion coefficient and tracer diffusion coefficients simultaneously from analysis of the interdiffusion composition profiles in a single experiment.