Compositional dependence of DC electrical conductivity of SrO-vanadate glasses

Direct current (DC) electrical conductivity and infrared (IR) spectroscopy studies were carried out on SrO-vanadate glasses with the nominal composition (V2O5)(x) (SrO)(1-x), 0.5 <= x <= 0.8 in an attempt to understand the nature of the mechanism governing the DC electrical conductivity and the effect of addition of V2O5 on the structure and electrical properties in these glasses. The glasses investigated in this paper were prepared by using melt quenching technique. XRD patterns confirm the amorphous nature of the present glasses and the actual compositions of the glasses were determined by ICP spectroscopy. The IR results agree with previous investigations on similar glasses and it has been concluded that Sr-vanadate glasses, studied in this investigation with 20 mol% SrO and greater would consist of a mixture of VO5 groups (Probably trigonal bipyramids) and VO4 metavandate chains with the Sr2+ ions occupying interstitial sites among the chains. The conductivity results were analyzed with reference to theoretical models existing in the literature and the analysis shows that the conductivity data are consistent with Mott's nearest-neighbor hopping model. However, both Mott VRH and Greaves models are suitable to explain the data. Schnakenberg's generalized polaron hopping model is also consistent with the temperature dependence of the activation energy, but the various model parameters such as density of states, hopping energy obtained from the best fits were found to be not in accordance with the prediction of the Mott model. (C) 2012 Elsevier B.V. All rights reserved.