Electrical charge transport and dielectric response in ZnO nanotubes

The AC electrical response of consolidated ZnO nanotubes was studied using impedance spectroscopy. The separation of grain and grain boundary properties was achieved using an equivalent circuit model. Modulus analysis provided additional information related to the charge transport properties. The frequency analysis of modulus properties showed a distribution of the relaxation time existing in the system. The activation energies calculated from the conductivity pattern and the relaxation time pattern were found to be nearly the same, which suggests that there is a link between these two phenomena. The dielectric absorption and dispersion behaviour of ZnO nanotubes as a function of frequency and temperature was studied. The real and imaginary part of the dielectric constant was found to increase with increasing temperature and found to decrease with increasing frequency. ► Transport properties and dielectric behaviour of ZnO nanotubes were analysed. ► Grain and grain boundary parameters were extracted from the equivalent circuit. ► Modulus analysis gave an evidence of localised and delocalised conduction. ► Asymmetric broadening of impedance peaks emphasised the poly-dispersive relaxation. ► ZnO nanotubes are very attractive for the applications in varistors.