Phase diagrams of II-VI/III-VI solid solutions with ordering tendencies

This paper describes a new procedure for the calculation of phase diagrams for quasiternary systems composed of quasibinary subsystems showing up to three ordering regions near special stoichiometric compositions. The system Hg3Te3/In2Te3/Ga2Te3 is used as an example. The phase diagrams for the subsolidus region are calculated from excess Gibbs energy functions that are modulated at the specified stoichiometric compositions by distribution functions of the Gauss type. These "Gaussian" terms consider the contribution of the composition and temperature dependent ordering energy to the excess Gibbs energy of the solid solution. If the energy of the solid state is described in this way by a single continuous Gibbs function, the thermodynamic factor for interdiffusion in such quasibinary systems can also be derived as a single continuous function. (C) 1999 Elsevier Science S.A. All rights reserved.