Thermodynamic Evaluation and Optimization of the As–Cd, As–Zn and As–Cd–Zn Systems

Abstract

In this work, a critical evaluation of all available phase diagrams and thermodynamic data for the As–Cd, As–Zn and As–Cd–Zn systems has been performed and thermodynamic assessments over the whole composition ranges are presented using the CALPHAD method. To predict thermodynamic properties and phase equilibria for these systems, the Modified Quasichemical Model for short range ordering was used for the liquid phase and the Compound Energy Formalism was used for the solid solutions. The optimized binary systems are in good agreement with existing experimental data. Within the ternary system predicted phase equilibria, the {text{ZnAs}}_{2}{-}{text{CdAs}}_{2} and {{text{Zn}}_{3}text{As}}_{2}{-}{{text{Cd}}_{3}text{As}}_{2} sections are in good agreement with the experimental data. Also, the eutectic temperature is accurately optimized for {text{ZnAs}}_{2}{-}{{text{Cd}}_{3}text{As}}_{2} and {{text{Zn}}_{3}text{As}}_{2}{-}{text{CdAs}}_{2}. However, the calculated liquidus of these two joins are less satisfactory compared to the experimental data. This is most likely due to the polymerization behavior of arsenic and its multivalence, which is not considered by the model used in this work.