Universal curve of ionic conductivities in binary alkali tellurite glasses

Abstract

The main objective of this work is to present an analysis and brief discussion of experimental ionic conductivity σ data in the binary alkali tellurite system, including on 47 glasses that extend the ionic conductivity range by more than 14 orders of magnitude in a wide compositional range. A 'universal' behavior is obtained, using log σ or log σT vs. E A/kgT, where EA is the activation enthalpy for conduction, kB is the Boltzmann constant and T is the absolute temperature. This finding further indicates the importance of a scaling factor F recently proposed, that is correlated to the free volume of glass composition. For a given value of EA/kBT, the difference between large and small values of G is only one order of magnitude in 87% of these glass systems. The influence of alkali content and temperature was minor on the pre-exponential terms, considering both expressions log10σ and log 10σT. Indeed, the pre-exponential term σ0 varies around an average value of 50 Ω-1cm-1 considering different compositions in this system. The fact that σ lies on these single 'universal' curves for so many ion-conducting binary tellurite glasses means that o is governed mainly by E4. The composition dependence of the activation enthalpy is explained in the context of the Anderson-Stuart theory.