Study of polaron transport mechanism in rare earth nano particles doped zinc-molybdenum-boro-tellurite glasses

Abstract

Erbium nanoparticles doped zinc-molybdenum-boro-tellurite glasses with chemical composition, (B2O3)0.1-(ZnO)0.1- (MoO3)0.3- (TeO2)0.50-x-(Er2O3)x (x = 0.01, 0.02, 0.03, 0.04 and 0.05) have been synthesized by the melt quenching technique. The samples were investigated for structure, density and dc conductivity as a function of temperature. Powder XRD studies revealed noncrystalline nature of the samples. Room temperature density of the glasses has been determined and molar volume has been estimated. Nature of variation of both density and molar volume with Er2O3 concentration revealed dynamic nature of the glass network. Temperature dependence of conductivity points out semiconducting behavior of the glasses. The conductivity at high temperature has been fit to Mott's small polaron hopping (SPH) model expression from which the Debye's temperature and activation energy were determined. Activation energy decreased for increase of mole fraction of Er2O3 which infers increasing hindrance to the polaronic motion developed with increase of Er2O3 concentration. Conductivity data deviated from Mott's SPH fit has been analyzed using Mott's VRH model and the density of states at fermi level has been determined. For the first time, erbium nanoparticles doped zinc-molybdenum-boro-tellurite glasses have been investigated for density and molar volume and their conduction mechanisms probed thoroughly. © 2019 Elsevier Ltd. All rights reserved.