Solid–Liquid Phase Equilibria for the Ternary Systems V2O5–Na2O–Fe2O3, V2O5–Na2O–Cr2O3, and V2O5–Na2O–MgO

Abstract

The phase equilibrium relationships of several vanadate systems have been studied by a combination of differential thermal analysis (DTA) and X-ray powder diffraction methods. All systems studied were eutectic in nature. The liquidus temperatures of the sodium vanadates were found to depend on the oxygen partial pressure for sodium oxide concentrations between 1.0 and 36 mol%. This effect was not observed for the ferric vanadate, chromic vanadate or magnesium vanadate systems. The solid–liquid phase equilibria for the ternary vanadate systems V2O5–Na2O–Fe2O3, V2O5–Na2O–Cr2O3, and V2O5–Na2O–MgO were measured by determining the temperature–composition data for various quasi-binary systems within each ternary system. Liquidus temperatures between 500 and 700 °C were found for those compositional ranges containing greater than 40 mol% V2O5 and between 10 and 60 mol% Na2O. The liquidus temperatures decreased with increasing oxygen partial pressure over much of the same compositional range.