Phase Equilibria in the Mn–V–O System near MnO–V2O3 Isopleth

Abstract

Phase equilibria in the MnVO system near MnOV2O3 isopleth has been investigated in the temperature range from 1200 degrees C to 1600 degrees C and in the range of oxygen partial pressure from similar to 10(-6) to similar to 10(-13) atm. High-temperature equilibration, quenching and electron probe microanalysis were employed to obtain equilibrium compositions of liquid and several solid solutions. XRD analysis was also employed to confirm the stable phases. The phases which have been observed are; liquid oxide, (MnO)(s.s)., (V2O3)(s.s.), and (MnV2O4)(s.s.). The (MnV2O4)(s.s). phase was confirmed to be the only intermediate phase near the MnOV2O3 isopleth under the conditions in the present study. It was found that sub-solidus phase equilibria are considerably affected by the oxygen partial pressure. From the effect of oxygen partial pressure on the subsolidus phase equilibria, the structures (Mn2+, V2+)T(Mn2+, Mn3+, Mn4+, V3+, Va)(2-x) O-O(4), (V3+, Mn3+, V4+)(2)O3+y and (Mn2+, Mn3+, V2+)(1-z)O are proposed for MnV2O4, V2O3, and MnO solid solutions, respectively.