Preparation and Properties of Stoichiometric Vanadium Oxides

Stoichiometric films of the V2O3–V2O5system, including the Magneli phases VnO2n– 1(3 ≤n≤ 9), were prepared by thermal oxidation of metallic vanadium between 720 and 950 K in quartz tubes evacuated to a residual pressure below 10–3Pa. The oxidation was performed in the presence of powder mixtures of two vanadium oxides with adjacent stability fields so as to ensure an oxygen partial pressure corresponding to the stoichiometry of the required vanadium oxide. The oxide films thus prepared showed a sharp metal–insulator transition, with a conductivity change comparable to that in single crystals.