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 sigma data in the binary alkali tellurite system, exemplified on 47 glasses that extent ionic conductivity by more than 14 orders of magnitude in wide compositional range. A universal finding is obtained using log sigma or log sigmaT vs. EA/kBT, where EA is the activation enthalpy for conduction, kB is the Boltzmann constant and T is the absolute temperature. This finding corroborates 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 to small values of sigma is only one order of magnitude in 87% of the glass systems considered. The influence of alkali content and temperature was minor on the pre-exponential terms, considering both expressions log10 sigma and log10 sigmaT. Indeed, the pre-exponential term sigma0 varies around an average value of sigma 50 1/Ohm.cm 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 sigma is governed mainly by EA. The activation enthalpy composition dependence is explained concerning the Anderson-Stuart theory