Thermodynamics of the V–O System : Dissociation Energies of VO and VO2

Abstract

The molecules vaporizing from V₂O₅(s) and VO(s) have been determined employing a mass spectrometer to analyze the vapors effusing from Knudsen cells containing these materials. The vapor over the V₂O₅ loaded cells was found to contain V₄O₁₀(g), V₆O₁₄(g), V₆O₁₂(g) with some evidence for V₄O₈(g) and V₂O₄(g). Since both the composition and the partial pressures varied with time no quantitative data could be obtained for these molecules. By contrast, both the composition and partial pressures of the vapor over VO(s) were essentially constant with time. The molecules observed were V(g), VO(g), and VO₂(g). A thermodynamic treatment of the data yields 6.4±0.2 ev and 12.8±0.2 ev, respectively, for the atomization energies of VO and VO₂.