Electrical DC conductivity in iron-containing bismuth-vanadate glasses

The DC conductivity, sigma , of 10 Bi2O3-(90-x)V2O5-xFe2O3 (mol.%) glasses, where x=0, 1, 3, 5, 10, 15, 20, 30 and 40, has been measured in the temperature range RT-200 degrees C. It has been found that for the ion-containing glasses log sigma versus 1/T plots obtained show a change in the slope near 110 degrees C. The activation energy, and the pre-exponential factor in the temperature range T>110 degrees C increases significantly with increasing Fe2O3 content. On the other hand, in the temperature range T<110 degrees C, these parameters increase weakly with increasing Fe2O3 content. The results are discussed in view of Mott's theory of small polaron hopping in the oxide glasses.