Thermodynamics of the Ca-CaO-CaF2 system

A static method was used to measure the partial vapor pressure of calcium over the Ca-CaO, Ca-CaF2, and Ca-CaO-CaF2 liquid solutions in the temperature range from 1165 to 1812 K. Simultaneously, the solubility of solid CaO or CaF2 in the melts was determined. All solutions are characterized by positive deviations from Raoult's law. The thermodynamic properties of the Ca-CaF2 melt were approximated by a subregular-solutions model with the ideal entropy term and those of Ca-CaO by a model that takes into account some ordering in molecular arrangement. The thermodynamic description of the ternary liquid solution was attained under the assumptions that interparticle interactions do not change in going from the binary constituent systems to the ternary one and that there is no triple interaction. The models were applied for the computation of phase diagrams of the studied systems.