Frequency and temperature dependent conductivity spectra of mixed transition metal oxide doped semiconducting glassy system

Abstract

Frequency and temperature dependent conductivity of mixed transition metal oxide (TMO) doped semiconducting glassy system, xV2O5–(1−x) (0.05MoO3–0.95ZnO) have been investigated in the wide range of frequency and temperature. The dc conductivity (σdc), crossover frequency (ωH), frequency exponent (n) and power law exponent (s) have been computed from the best fitted plots of experimental data. We have estimated the values of activation energy of ac conduction (Eac) and free energy of polaron migration (EH). Dc conductivity of the as-prepared samples shows thermally activated non–linear nature, which has been interpreted with Vogel–Tammann–Fulcher (VTF) model. From the fitting, pseudo activation energy (Ea) and thermodynamic ideal glass transition temperature (T0) have been estimated. Nature of variation of conductivity and the power law exponent (s) data exhibit that non–overlapping small polaron tunnelling (NSPT) model is suitable to interpret these data for compositions x=0.3, 0.5 and 0.7. On the other hand, correlated barrier hopping (CBH) model is most applicable mechanism for ac conduction for compositions x=0.9 and 0.93. Formation of some complex Mo-O-V structures may be possible reason for applicability of CBH model for composition x=0.9, 0.93. It is also observed that conductivity relaxation process of charge carriers (polarons) is independent of temperature, but depends upon composition.