Phase diagram and thermodynamic properties in the VWO system at high temperatures I. In a region WWO 2VO 2V 2O 3

Abstract

The phase relation within a region, WWO 2VO 2V 2O 3 in the VWO system, was examined at 1173K and 1373K by using a vacuum seal technique and the TG method. The dissociation pressure of oxygen for V xW 1−xO 2 (0<x<1) was measured by using the EMF method at temperatures from 1173K to 1373K. The detailed phase diagram in the region, WWO 2VO 2V 2O 3, containing the complicated coexisting boundaries of the V xW 1−xO 2 and V nO 2n−1 (n:integer. ≥2) could be established at these temperatures. The standard Gibbs energy change of the formation of V 0.5W 0.5O 2 was calculated from the equilibrium partial pressure of oxygen.