Thermodynamic analysis of the system Fe2O3-FeTiO3

The cluster variation method, in the single prism approximation, is used to model phase relations in the system, Fe₂O₃-FeTiO₃. Ordering in FeTiO₃ is analyzed, and it is shown that the stabilization of FeTiO₃ (relative to mechanical mixing of Fe₂O₃ and Ti₂O₃) includes: (1) a contribution from the redox reaction, Fe³⁺+Ti³⁺→Fe²⁺+Ti⁴⁺ (ΔH _redox～?70kJ mole^?1); and (2) a contribution from ordering (ΔH _OD～?8kJ mole^?1). A theoretical phase diagram is presented and compared with available experimental data. Semiquantitative agreement between theory and experiment (on the location of phase boundaries) is achieved; but, owing to the paucity of experimental data on coexisting phases, these results may be fortuitous.