Study of dielectric relaxation behavior of composites of Poly (vinyl alchohol) (PVA) and Reduced graphene oxide (RGO)

摘要

The composite films of Poly (vinyl alcohol) (PVA) and Reduced graphene oxide (RGO) with 1 wt%, 1.5 wt% and 2 wt% loading of RGO using solution mixing have been prepared via evaporative casting technique. For this purpose, RGO has been chemically synthesized using modified Hummer's method and characterized using UV Visible absorption, Fourier Transform Infrared (FTIR) spectroscopy and Transmission electron Microscopy (TEM). Further, the chemical interaction of PVA chains with RGO has been revealed using FTIR spectroscopy. The variation in dielectric parameter (epsilon' and epsilon") with frequency has been studied at different temperatures (320 K-400 K) in order to epitomize the dielectric relaxation behavior in the prepared composite films. The values of e' and e" have been found to increase with rise in temperature and loading of RGO. The almost linear variation in ac conductivity (sigma(ac)) with frequency at each studied temperature suggests the observation of universal power law in these composites. However, the slope of these curves was found to decrease with rise in temperature suggesting the Correlated Barrier Hopping (CBH) model as charge transport mechanism in these composites. The non-symmetric shape of electric modulus (M") variation indicate the existence of non-Debye type of relaxation. The relaxation time (tau) determined from M" variation with frequency is found to be decreased with rise in temperature. This elucidates the transition of long range to short range mobility of charge carriers with rise in temperature. Further, as an effect of increase in RGO concentration in composites, increase in tau has been found depicting their use in energy storage applications where materials with longer discharging time are required.