Polaronic conduction in barium borate glasses containing iron oxide

The conductivity of xFe(2)O(3) . (60 - s)BaO . 40B(2)O(3) glasses can be de scribed using Mott's models for the small polaron hopping and variable-rang e hopping processes. The change of resistivity and activation energy with c omposition indicates that the conduction process varies from ionic to polar onic one. The activation energy is the predominant parameter that affects t he conductivity with composition. The calculated values of the conductivity parameters indicate that the conduction mechanism is adiabatic in nature. The change in both the density and molar volume was discussed in terms of t he structural modifications that take place in the glass matrix upon replac ing BaO by Fe2O3. (C) 2001 Elsevier Science B.V. All rights reserved.