Interaction of vanadium (5) oxides with holmium and erbium oxides

Phase equilibria in binary systems of vanadium (5) oxide - oxide of rare earth element (holmium and erbium) within the concentration range of 0 - 50 mol.% of r.e.e. oxide have been studied by the differential thermal, X-ray phase, and chemical analyses. At 670 deg C the corresponding orthovanadates are formed which give eutectics with vanadium oxide and melt congruently at 1670 and 1680 deg C, respectively. The heat (kcal/mol) of the reactions of holmium and erbium orthovanadates formation from oxides (-39.7 and -39.9, respectively) have been determined, and enthalpy values of the formation of holmium and erbium orthovanadates (-446.1 and -448.5) at 943 K have been calculated