Critical evaluation and thermodynamic reassessment of the Na2O-SiO2 system

Abstract

Thermodynamic investigation of the Na₂O-SiO₂ system is extremely significant for the silicate glass industry and the control of Na₂O balance in the input materials of blast furnaces. The Na₂O-SiO₂ system has been thermodynamically assessed numerous times in the previous studies. However, the phase equilibria in the Na₂O-rich side remain inadequately described. Consequently, the Na₂O-SiO₂ system was reassessed by the CALPHAD approach in the present work. The liquid phase was described by using the two-sublattice partially ionic liquid model (Na⁺¹)_P(O⁻²,SiO₄⁻⁴,SiO₂)_Q and six intermediate compounds were treated as stoichiometric compounds due to their limited solid solubilities. A set of self-consistent thermodynamic parameters was then obtained, and the experimental phase diagram data and thermodynamic properties can be satisfactorily reproduced by the calculation within the experimental errors. The present thermodynamic parameters contribute to the composition design of silicate glass and the formulation of input materials in blast furnaces.