The thermodynamics of mixing and its dependence on cation distribution in the Fe3O4–Fe2TiO4 (magnetite-ulvöspinel) spinel solid solution were studied using high-temperature oxide melt solution calorimetry and a range of structural and spectroscopic probes. The enthalpies of formation of ilmenite and ulvöspinel from the oxides and from the elements were obtained using oxidative drop solution calorimetry at 973 K in molten sodium molybdate. The enthalpy of mixing, determined from the fit to the measured enthalpies of drop solution calorimetry, is endothermic and represented by a quadratic formalism, ΔHmix = (22.60 ± 8.46)x(1 − x) kJ/mol, where x is the mole fraction of ulvöspinel. The entropies of mixing are more complex than those for a regular solution and have been calculated based on average measured and theoretical cation distributions. Calculated free energies of mixing show evidence for a solvus at low temperature in good agreement with that observed experimentally.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.