Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn\(_{2}\)O\(_{3}\)-SiO\(_{2}\) and FeO-Fe\(_{2}\)O\(_{3}\)-MnO-Mn\(_{2}\)O\(_{3}\)-SiO\(_{2}\) Systems

A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn\(_{2}\)O\(_{3}\)-SiO\(_{2}\) and FeO-Fe\(_{2}\)O\(_{3}\)-MnO-Mn\(_{2}\)O\(_{3}\)-SiO\(_{2}\) systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25 \(^{\circ }\)C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe\(_{2}\)SiO\(_{4}\)-Mn\(_{2}\)SiO\(_{4}\)) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO\(_{3}\)-FeSiO\(_{3}\)) and braunite (Mn\(_{7}\)SiO\(_{12}\) with excess Mn\(_{2}\)O\(_{3}\)) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)\(_{3}\)O\(_{4}\)) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237–246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.