Universal curve of ionic conductivities in binary alkali tellurite glasses

The main objective of this work is to present an analysis and brief discussion of experimental ionic conductivity a 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 sigma or log sigma T vs. E-A/k(B)T, where E-A is the activation enthalpy for conduction, k(B) 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 E-A/k(B)T, the difference between large and small values of a 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 log(10)sigma and log(10)sigma T. Indeed, the pre-exponential term sigma(0) varies around an average value of 50 Omega(-1) cm(-1) considering different compositions in this system. The fact that sigma lies on these single 'universal' curves for so many ion-conducting binary tellurite glasses means that a is governed mainly by E-A. The composition dependence of the activation enthalpy is explained in the context of the Anderson-Stuart theory.