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) = Wo(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.