DC electrical properties and non–adiabatic small polaron hopping in V2O5–CdO–ZnO glass nanocomposites

Abstract

Semiconducting transition metal oxide (TMO) doped glass nanocomposites xV₂O₅–(1–x) (0.05CdO–0.95ZnO), x=0.3, 0.5, 0.7 and 0.9 have been prepared by melt quenching method. DC electrical conductivity of as prepared glass nanocomposites is are investigated over a wide temperature range. Formation of small polarons has been confirmed from dc electrical conductivity experimental data, whereas conductivity is due to mainly polaron hopping from V⁺⁴ to V⁺⁵ valence state in these glassy systems. Temperature dependent conductivity data have been analyzed using the small polaron hopping (SPH) model. Low, high temperature activation energy, optical phonon frequency and Debye’s temperature have been determined. Conductivity data have been analyzed in view of Mott’s variable range hopping (VRH) models and Greaves VRH models; the density of states at the Fermi level has been evaluated. Various polaron hopping parameters such as polaron radius, polaron binding energy, polaron band width and polaron coupling constant (γ_P) have been estimated. It has been ascertained by these estimated quantities and different approaches that the nature of hopping conduction is non–adiabatic variable range hopping of small polarons. The evaluated values of hopping carrier mobility (μ) and hopping carrier concentration (N_C) are found to depend on composition and temperature.