The effect of the random glass structure on the conductivity of amorphous V₂O₅

Abstract

The observed activation energy of the d.c. electronic conductivity of amorphous V₂O₅ and some V₂O₅-containing glasses obeys W(T) = W_o(1 - θ/T) for T>225 K, with θ ≃ 70 K. This temperature dependence is ascribed to the effect of the random glass structure on the mobility of the hopping small polarons. A model in which the hopping energy varies with the hopping distance gives a satisfactory account of the data; site disorder and percolation models do not. The random glass structure contributes typically 0.09 eV to an average hopping energy of 0.7 eV. The conductivity increases smoothly with the ratio c = V⁴⁺/(V⁴⁺ + V⁵⁺) up to c = 0.35. The addition of other oxides to V₂O₅ increases the hopping energy and changes the pre-exponential factor.