Preparation and properties of stoichiometric vanadium oxides

Stoichiometric Trims of the V2O3-V2O5 system, including the Magneli phases VnO2n-1 (3 less than or equal to n less than or equal to 9), were prepared by thermal oxidation of metallic vanadium between 720 and 950 K in quartz t ubes evacuated to a residual pressure below 10(-3) Pa. The oxidation was pe rformed in the presence of powder mixtures of two vanadium oxides with adja cent stability fields so as to ensure an oxygen partial pressure correspond ing to the stoichiometry of the required vanadium oxide. The oxide films th us prepared showed a sharp metal-insulator transition, with a conductivity change comparable to that in single crystals.