Dielectric relaxation and electric modulus of polyvinyl alcohol-Zinc oxide composite films

A systematic study of AC electrical properties and dielectric relaxation of polyvinyl alcohol (PVA)-zinc oxide (ZnO) composite films has been presented in the frequency range 1 Hz-100 kHz when temperature changes from 288 K-353 K. The films were characterized for structural analysis by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) attached with EDAX and Fourier transform infrared spectroscopy (FTIR). The structural investigation confirms the presence of ZnO in PVA polymer. The incorporation of ZnO particles into PVA matrix enhances the AC conductivity and temperature dependence of them obeys the Jonscher's universal power law. The frequency exponent which depends on temperature suggests the CBH (correlated barrier hopping) mechanism; is dominent mechanism in the composite film. The real and imaginary part of dielectric constant shows dispersion at low frequencies and decreased at high frequencies which may be ascribed to interfacial or electrode polarization. The temperature dependence of epsilon ' follows the Debye model. At low frequency, the values of a real part of the electric modulus (M ') remains almost zero at all temperature except at 288 K and 303 K temperature due to viscous nature of polymer at low temperatures. The dielectric relaxation time was extracted from a plot of frequency dependence of M '' at different temperature and it is found to decrease with temperature resulting in the enhancement of AC conductivity.