Thermal and electrical properties of some single and mixed transition-metal ions-doped tellurite glasses

Abstract

Two sets of tellurium-based glasses doped with vanadium and vanadium-cobalt oxides have been prepared by melt quench method and investigated for density, glass-transition temperature, specific-heat capacity and dc electrical conductivity in the temperature range 300-500 K. Thermal stability, fragility and glass-forming tendency in these systems have been estimated. Thermal stability of these glasses was found to be larger than for similar systems. The dc electrical conductivity has been analyzed in the light of Mott's small polaron hopping (SPH) and Mott's and Greave's variable range hopping (VRH) models. The electrical conduction was confirmed to be due to non-adiabatic SPH. The conductivity behavior at temperatures above TD (=?D/2) (where ?D is Debye's temperature) was found to be in agreement with Mott's SPH model and at low temperatures behaved in accordance with Mott's VRH model. The temperature regions in which Mott's SPH and VRH models hold for the present systems are found to be different from similar systems already reported. Various physical parameters in these models such as, activation energy, polaron hopping energy, etc., were determined. It is for the first time that the above-mentioned properties have been investigated for the present mixed transition-metal ions-doped glasses. © 2008 Elsevier B.V. All rights reserved.