Mass Spectrometric Thermodynamic Study of the Fe2O3–TiO2 System

High-temperature differential mass spectrometry was used to study the vaporization processes and thermodynamic properties of samples of the Fe2O3–TiO2 system containing 25, 35, and 45 mol. % iron oxide. As shown earlier, at temperatures above 1400 K, Fe2O3, losing oxygen, turns into FeO. Therefore, in this article, a mass spectrometric thermodynamic study of the FeO–TiO2 system was carried out at a temperature of 1760 K. The composition and partial pressures of vapor, as well as the values of FeO activities and excess Gibbs energy in the FeO–TiO2 system were determined. Using the Wilson polynomial made it possible for the first time to estimate the mixing enthalpy and excess entropy in the FeO–TiO2 system at 1760 K. The thermodynamic properties of melts of the FeO–TiO2 system at 1760 K were modeled using the generalized lattice theory of associated solutions, and the relative numbers of bonds of various types in the model melt lattice were calculated, indicating the preferential formation of Fe–O–Ti bonds at a FeO content of 55 mol %. It is shown that at a temperature of 1760 K, the found values of the excess Gibbs energy in the FeO–TiO2 system are evidence of negative deviations from the ideality.