Model calculations of phase stabilities of oxide solid solutions in the CoFeMnO system at 1200°C

Abstract The thermodynamics of the spinel and rock-salt structure phases of the system CoFeMnO at 1200°C have been investigated with regard to their relation to the phase equilibria between these phases. To describe the thermodynamics of the spinel phase, a sub-lattice model, based on the cation distribution of 2+ and 3+ ions between octahedral and tetrahedral sites has been used. In the modelling, the influence of deviations from stoichiometry has been taken into account for the rock-salt structure phase. A set of thermodynamic parameters has been derived which allows the calculation of the compositions of the spinel and rock-salt structure phases at equilibrium as a function of oxygen partial pressure at 1200°C. The model also permits the calculation of the cation distribution in the ternary spinel phase at all compositions.