Activity-composition relations in FeTiO3-MnTiO3 ilmenite solid solutions from EMF measurements at 1050?1300 K

Abstract

The activity of FeTiO3 in the binary ilmenitepyrophanite (FeTiO3-MnTiO3) solid solution has been determined for the temperature range 1050–1300 K by displacement of the reaction: 2 FeTiO3=2 Fe+2 TiO2+O2 in T-μO2 space, using an electrochemical technique with calcia- and yttria-stabilized zirconia solid electrolytes. The activities show small positive deviations from ideality, which, although the data are unusually precise, may be perfectly described by the simple regular solution model, with an interaction parameter, W Fe-Mn ilm , of 2.2±0.3 kJ g-atom−1, which is independent of temperature. This value, together with the experimental data on the partitioning of Fe and Mn between ilmenite and garnet (Pownceby et al. 1987), gives W Fe-Mn gt =1.2±0.5 kJ g-atom−1 for the almandine-spessartine (Fe3Al2Si3O12-Mn3Al2Si3O12) solid solution.