Thermodynamic activities of FeO in CaO‐FeO‐SiO₂ slags

In the present work, a thermodynamic model to describe the activities of components in complex slag systems based on a Temkin approach has been put forward. The model was applied to the ternary system CaO‐“FeO”‐SiO 2 in order to calculate the activities of FeO as a function of temperature and composition from literature data. For this purpose, the experimental data on the activity of FeO available in literature were complemented in the present work by ZrO 2 ‐CaO solid electrolyte galvanic cell measurements for some selected compositions. An assessment of the data for the binary systems FeO‐SiO 2 and CaO‐FeO was carried out. The computed ternary activities are presented in the form of iso‐activity lines at 1673 and 1873K. On the basis of the model predictions, the reliability of the solid electrolyte method for such measurements is discussed.