Effect of ZnO nanoparticles and temperature on dielectric constant/loss properties of polystyrene nanocomposite films

In the present work, pristine and ZnO-doped polystyrene (PS) nanocomposite films were synthesized using solution-mixing technique. These films have been synthesized with different concentrations of ZnO, i.e. 5, 10, 15 and 20 wt% to PS matrix. The main emphasis of this study is to investigate the effect of ZnO nanopowder on the dielectric properties of PS matrix. Dielectric constant/loss of these PS nanocomposite films was examined as a function of frequency (from 100 Hz to 300 kHz) and temperature (from 293 to 443 K). Overall increase in dielectric constant, i.e. from 7.5 to 9.3 (at room temperature) and 7.7 to 9.5 (at 443 K), and dielectric loss, i.e. from 0.08 to 0.18 (at room temperature), was observed after the incorporation of ZnO in PS matrix. Change in dielectric constant and loss values of nanocomposite films is attributed to the increased water absorption capability and defects/traps arise in nanocomposite films. These configurational changes were confirmed by different characterization techniques, viz. Fourier transform infrared and photoluminescence techniques. Cole-Cole distribution function has been employed to investigate the variation in dielectric relaxation phenomenon due to the insertion of ZnO in PS matrix. Different parameters like mean relaxation time, molecular relaxation time, dipolar relaxation strength and dielectric strength are calculated from the experimental data. Significant changes in dipolar relaxation strength, i.e. from 0.13 to 0.51 and 0.36 to 0.69, were observed at 293 K and 443 K temperature, respectively, with the increase in wt% of ZnO.