Thermodynamic description of the M2O–SiO2 (M = K, Na) systems

The phase diagrams of the M2O–SiO2 (M = K, Na) binary systems were assessed using the Calculation of Phase Diagram (CALPHAD) technique. The thermochemical and phase equilibrium information taken from the literature for these two binary systems have been evaluated, and a series of thermodynamic parameters was obtained to describe each phase in these systems. The liquid phase was described by the ionic two-sublattice model with the formula ( M + 1 ) P ( O - 2 , SiO 4 - 4 , SiO 2 0 , Va - ) Q (M = K, Na). The heat capacities of solid phases were taken into consideration in this optimization process, a brief review of which is given in this work. The calculated phase equilibria were found to be in agreement with available experimental data.