Optical and dielectric properties of ZnO-PVA nanocomposites

Nanocomposites of polyvinyl alcohol and ZnO were prepared using the solution casting method. ZnO nanoparticles with hexagonal wurtzite structure and mean sizes of 59, 82 and 150 nm were prepared by thermal decomposition of zinc acetate dihydrate. The synthesized crystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) Optical properties of the nanocomposites were determined using UV visible absorption spectroscopy. The results showed that all samples appeared near band edge absorption close to the bulk value. Furthermore, broadband dielectric spectroscopy, at ambient temperature, was employed in order to investigate the effect of mean particle size upon interfacial relaxation phenomena. Dielectric data provide evidence that interfacial polarization, which is present in all three nanocomposite films, shifts to higher frequencies and its intensity is decreasing as the mean nanoparticle diameter is also decreasing. Finally exploiting the Cole Davidson approach, becomes evident, that interfacial polarization process acquires a more symmetric form, tending to a pure Debye relaxation. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.