Immiscibility in the Fe3O4–FeCr2O4 spinel binary

摘要: The solid solution behavior of the Ni(Fe{sub 1-n}Cr{sub n}){sub 2}O{sub 4} spinel binary is investigated in temperature range 400-1200 C. Non-ideal behavior, as exhibited by non-linear changes lattice parameter with n, observed a series single-phase solids air-cooled from 1200 Air-annealing for one year at 600 C resulted partial phase separation having n = 0.5. Spinel crystals grown NiO, Fe{sub 3} and Cr{sub reactants, mixed to give NiCrFeO{sub 4}, Ostwald ripening molten salt solvent, single stability down about 750 (the estimated consolute temperature, T{sub cs}). A solvus exists below cs}. becomes increasingly asymmetric lower temperatures extrapolates values 0.2 0.7 300 extrapolated shown be consistent that predicted using primitive regular model which free energies mixing are determined entirely configurational entropy room temperature.