Electrical conductivity and hopping conduction mechanism by VRH model in halide modified tellurite glasses

Abstract

Electrical properties of halide doped tellurium glasses with composition 60TeO2-(25-x) Bi2O3-15B2O3-x ZnCl2, where x varies from 0 to 20 with step-size 5 has been studied in frequency range 10-1 Hz–105 Hz and temperature range of 200°C–300°C. The frequency-dependent conductivity was found to obey Almond-West's universal powers law and parameters such as frequency exponent (s), DC conductivity, and crossover frequency were obtained by fitting the ac conductivity experimental data with Almond-West's universal powers law. Based on estimated s values the electrical conduction model was depicted, and it was found that the correlated barrier hopping (CBH) model provides a pretty realistic depiction of the primary AC conduction mechanism. Further, the migratory enthalpy (Hm) and the enthalpy required to remove the cation from its initial position near a charge-compensating centre (Hf) were calculated. Further, Variable range hopping, or VRH, was found to be the process by which charges move between localized states.The electric modulus (M″) fitting with the Kohlrausch-Williams-Watts (KWW) function revealed non-Debye-type relaxation in the examined glass samples. Activation energy estimated from conductivity (1.13–1.20 eV), and electric modulus (1.13–1.22 eV) analysis are in good agreement indicating that polarons had to overcome a constant energy barrier throughout both the relaxation and conduction phases. One master curve was produced for all compositions and temperatures as a result of an impressive convergence in the scaling spectra of the AC conductivity and electric modulus (M′ and M″). Therefore, it was concluded that neither temperature nor composition impacted the conduction or relaxation mechanisms seen in the glass samples under study. The dielectric properties studies suggested non-debye type behavior.