Thermodynamic Optimization And Calculation Of Phase Diagrams Related To The Rare Earth Halides (Ⅲ) And The Alkali Metal Halides Or Alkali Earth Metal Halides

By using CALPHAD(Computer Coupling of Thermo-chemistry and Phase Diagram)technique the optimization and calculation of the binary systems of ErCl₃-MCl(M= Li,Na,K,Rb,Cs),H0Cl₃-MCl(M= Na,K, Rb,Cs),DyCl₃-MCl(M= Rb,Cs),ErCl₃-CaCl₂ were carried out.For describing the Gibbs energies of liquid phase in these systems,the new modified quasi-chemical model in the pair-approximation for short-range ordering were used.According to the characters of the rare earth halide phase diagrams,simple software was applied to calculate them.In the course of optimization,thermodynamic models were chosen firstly.Then from measured phase equilibrium data and parts of experimental integral properties the ErCl₃-MCl(M= Li,Na,K,Rb,Cs), HoCl₃-MCl(M= Na,K,Rb,Cs),DyCl₃-MCl(M= Rb,Cs),ErCl₃-CaCl₂ phase diagrams were optimized and calculated.A set of thermodynamic functions were gotten based on interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.By analyzing the calculated phase diagrams and the experimental ones,we checked up and complemented some parts of experimental phase diagrams.Furthermore discussion about the enthalpy of mixing in those systems was taken,and some principles were proven: the enthalpy of mixing decreases with the increasing of the radius of Alkali metal ion from Li⁺ to Cs⁺;moreover the broad minimum values of the interactive coefficients were found at the 25%mole fraction of rare earths halides,which represented the characters of short-range ordering. For simple Eutectic system,thermodynamic property emerges weak negative error versus ideal solution.Enthalpy of mixing and interactive coefficient is all large.