Mass spectrometric thermodynamic study of the $\rm Fe_2\rm O_3$–$\rm TiO_2$ system

High-temperature differential mass spectrometry was used to study the vaporization processes and thermodynamic properties of samples of the $\rm Fe_2\rm O_3$–$\rm TiO_2$ system containing $25{,}~35{,}$ and $45$ mol. $\%$ iron oxide. As shown earlier, at temperatures above $1400$ K, $\rm Fe_2\rm O_3$, losing oxygen, turns into $\rm FeO$. Therefore, in this article, a mass spectrometric thermodynamic study of the $\rm FeO$–$\rm TiO_2$ system was carried out at a temperature of $1760$ K. The composition and partial pressures of vapor, as well as the values of $\rm FeO$ activities and excess Gibbs energy in the $\rm FeO$–$\rm TiO_2$ system were determined. Using the Wilson polynomial made it possible for the first time to estimate the mixing enthalpy and excess entropy in the $\rm FeO$–$\rm TiO_2$ system at $1760$ K. The thermodynamic properties of melts of the $\rm FeO$–$\rm TiO_2$ 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 $\rm Fe$–$\rm O$–$\rm Ti$ bonds at a $\rm FeO$ content of $55$ mol $\%$. It is shown that at a temperature of $1760$ K, the found values of the excess Gibbs energy in the $\rm FeO$–$\rm TiO_2$ system are evidence of negative deviations from the ideality.