Thermodynamic modeling of the (Al2O3 + Na2O), (Al2O3 + Na2O + SiO2), and (Al2O3 + Na2O + AlF3 + NaF) systems

All available thermodynamic and phase diagram data for the condensed phases of the (Al2O3 + Na2O), (Al2O3 + Na2O + SiO2), and (Al2O3 + Na2O + AlF3 + NaF) systems have been critically assessed. Model parameters for solid solutions and a single set of parameters for the liquid solution in the binary, ternary, and ternary reciprocal systems have been optimized and permit to reproduce most of the critically reviewed experimental data. The Modified Quasichemical Model in the Quadruplet Approximation was used for the oxyfluoride (mixture of molten oxides and salts) liquid solution, which exhibits strong first-nearest-neighbor and second-nearest-neighbor short-range order. This thermodynamic model takes into account both types of short-range order as well as the coupling between them. The charge compensation effect present in the (Al2O3 + Na2O + SiO2) system was taken into account by adding a (NaAl)4+ species in the liquid solution.

► We modeled Al2O3–Na2O–SiO2 and Al2O3–Na2O–AlF3–NaF using the Modified Quasichemical Model in the Quadruplet Approximation.
► This assessment includes a very thorough review of all available experimental data for Al2O3–Na2O and Al2O3–Na2O–SiO2.
► The charge compensation effect in the SiO2-rich region of the (Al2O3 + Na2O + SiO2) system is modeled with a NaAl4+ cation.
► First detailed thermodynamic modeling of the (Al2O3 + Na2O + SiO2) ternary system.
► First thermodynamic modeling at all compositions and temperatures of the (Al2O3 + Na2O + AlF3 + NaF) reciprocal oxyfluoride system.