Thermodynamic properties of NiCr2O4-NiFe2o4 spinel solid solution

Abstract

The tie lines delineating ion-exchange equilibria between NiFe2O4- NiCr2O4 spinel solid solution and Fe2O3Cr2O3 corundum solid solution were determined at 900, 1000, and 1200 °C by electron microprobe and energy dispersive X-ray analysis of oxide phases, using the flux growth technique. Activities of the spinel components were calculated from the tie lines, assuming Temkin's ideal mixing in the corundum solid solution. The spinel phase could be expressed by a regular solution with negative deviations from ideality. The Gibbs free energies of mixing for spinel solid solution were discussed in terms of the cation distribution model, based on site preference energies and assuming random mixing on both tetrahedral and octahedral sites.