Phase Relations in the System MgO-V2O3-VO2 at 1200°C

Phase relations in the quasi-ternary system MgO-V₂O₃-VO₂ at 1200°C were studied using the quenching technique under controlled O₂ atmospheres. A new phase of a type z VO _y Mg_{2? x} V_{1+ x} O₄ (0< x <1, y ≥1.5, z >0) was found with a compositional region along the MgV₂O₄-Mg₂VO₄ join. Equilibrium P _{O 2} observed for Mg_{2? x} V_{1+ x} O₄ is quite different from that for V _n O_{2 n -1} with an equal ratio of V³⁺/V⁴⁺, corresponding to the V³⁺ stabilities in two types of compounds. Thus, the phase relations in the ternary system were constructed on a conventional triaxial diagram as a function of P _O2.