High-temperature phase relations and thermodynamics in the iron-titanium-oxygen system

Phase equilibria and thermodynamics in the FeO-TiO2-Ti2O3 ternary system we re studied at 1500 degrees C and 1600 degrees C. In particular, the liquid slag-phase region and its saturation boundary with respect to metallic iron , titania, and lower titanium oxides was investigated. The liquid slag-phas e region extends substantially toward an anosovite (Ti3O5) composition, and considerable concentrations of divalent iron coexist with trivalent titani um in the liquid-slag phase. This seems to be a consequence of the complete solid solution between ferrous pseudobrookite (FeTi2O5) and anosovite (Ti3 O5), which exists at subsolidus temperatures. The liquid-slag field is sign ificantly enlarged toward the anosovite composition upon increasing the tem perature from 1500 degrees C to 1600 degrees C. Activities of the component s "FeO" and TiO2 in the liquid-slag region were determined by Gibbs-Duhem i ntegration of the measured oxygen partial pressures at 1500 degrees C, The FeO shows moderate negative deviation, while titania shows a slight negativ e deviation in FeO-rich slags and a positive deviation in high-titania slag s. The experimentally measured activity values were modeled using regular a nd biregular solution models, and good agreement was obtained with the bire gular solution model.