THE ASSESSMENT OF THERMODYNAMIC PARAMETERS IN THE FE-O AND FE-SI-O SYSTEMS

Abstract

Thermodynamic data for phases in the Fe-Si-O system have been assessed using experimental information on phase equilibria, electrochemical measurements of oxygen activity, calorimetry, and elastic property measurements. The sublattice model was applied to magnetite, wustite, and liquid phase. To get consistency between two sets of experimental data on subsolidus phase equilibria in the Fe-O system at 1 bar and in the Fe-Si-O system at pressures up to 20 GPa and temperatures up to 2000 K, the thermodynamic data for solid phases has been optimized (the volumetric properties for fayalite, magnetite, and ferrosilite, enthalpy and heat capacity for fayalite, enthalpy, and entropy for ferrosilite and γ-spinel). Thermodynamic properties of liquid phase (Gibbs free energy of Fe2SiO4 endmember and mixing parameters) have been reassessed to reach consistency with experimental data. Parameters in the Fe-FeO system have been evaluated up to 16 GPa. The assessment of liquid mixing parameters in the Fe-Si-O system has been made only at 1 bar, due to the lack of experimental data at high pressures.