Ac conductivity of transition metal oxide doped glassy nanocomposite systems: temperature and frequency dependency

Abstract

Transition metal oxide (TMO) doped different types of semiconducting glassy systems of the common terminology as 0.3V2O5–0.7 (0.05AmOn–0.95ZnO) for AmOn = MoO3, SeO2, Nd2O3, and CdO have been prepared by melt quenching route. The frequency and temperature dependent conductivity of all the as-quenched glass nanocomposite samples has been investigated over a wide temperature and frequency range. Conductivity, depending on temperature and frequency, is well established using Jonscher’s universal power law and Almond-West formalism. The values of DC conductivity (σdc), polaron hopping frequency (ωH), frequency exponent (n), and power law exponent (s) have been computed. The value of n indicates three-dimensional motions of charge carriers or polarons, which is the main reason for high-frequency dispersion in the ac conductivity. The estimated values of activation energy of ac conduction (Eac), free energy of polaron migration (EH) and activation energy of DC conductivity (Edc) are mainly owing to polaron transport with the energy level in the optical band gap. Ac conductivity and temperature dependent power-law exponent (s) of the as-prepared glassy samples containing MoO3 and Nd2O3 are dominated by non-overlapping small polaron tunneling (NSPT). Conversely, correlated barrier hopping (CBH) solely controls the ac conductivity and temperature dependent power-law exponent (s) of the glassy samples containing SeO2 and CdO. It is ascertained that mobile charge carrier concentration is independent of temperature and only 20%–25% of the total charge carriers (polarons) contribute to the ac conductivity of the presently studied glassy systems.