Solid-liquid equilibria in ternary regular associated solutions

Abstract

The model of Regular Associated Solutions, developed by A.S. Jordan for binary systems, has been extended to 3-component systems. Expressions for the activity coeffi-cients have been obtained, which satisfy the Gibbs-Duhem equation. The activity coefficients are identical with those found by Jordan when the first or second component is absent. At the pseudo-binary cut the activity coeffi-cients γAC and γBC are identical with those for regular solutions. Equations relating the temperature and compo-sitions of the solid and liquid phases were used in the general form given by Laugier but without the approxima-tions he used to express the mole fractions of the com-pounds formed in the liquid phase. These mole fractions can be found by a simple numerical procedure. It is pro-posed to solve the solid-liquid equilibrium equations with respect to the temperature and solid compositions by the Newton-Raphson method, neglecting the weak temperature dependence of the mole fraction ratios xAC/xAC and xBC/xBC- The liquidus surface and the solid composition surface are calculated for the system zinc-cadmium-tellurium based on the experimental liquidus temperatures obtained by Steininger, Strauss and Brebrick and using the model developed here.