The Phase Equilibria in the FeO-Fe2O3-V2O3 System at 1500°K

Abstract

Abstract The phase equilibria in the FeO–Fe2O3–V2O3 system have been determined at 1500°K by varying the oxygen partial pressure. The following three oxide phases have been stable in equilibrium: a sesquioxide solid solution with a corundum-type structure (approximate composition Fe2O3–V2O3), a ternary solid solution with a spinel type structure (approximate composition FeO·Fe2O3–FeO·V2O3), and a ternary wüstite solid solution with a periclase-type structure which dissolves vanadium ions up to about 10 mol per cent. The extent of the solid solution areas and the location of the oxygen isobars have been determined. The spinel phase coexisted partly with metallic iron and partly with the wüstite solid solution, corresponding to lower and higher iron contents respectively. The standard free energies of the Fe+V2O3+\frac12O2=FeV2O4 and 0.05 Fe+V2O3+Fe0.95O=FeV2O4 reactions to produce FeV2O4 have been calculated to be −45500±200 cal and −5800±400 cal respectively at 1500°K on the basis of the equilibrium oxygen partial pressure.