Electric modulus approach to the analysis of electric relaxation and magnetodielectric effect in reduced graphene oxide–poly(vinyl alcohol) nanocomposite

Abstract

The polymers poly(vinyl alcohol) (PVA) is used as matrices to synthesize a nanocomposite with reduced graphene oxide (rGO). The structural and optical properties of the rGO and the nanocomposites (rGO–PVA) are studied by XRD, FTIR analysis, FESEM studies, Raman spectroscopy and UV–VIS absorption spectroscopy analysis. Interaction of PVA polymer chains with rGO is confirmed from FTIR study. The bandgap of the PVA and rGO–PVA nanocomposites has been studied from UV–VIS absorption spectrum. The refractive index and optical dielectric constants of PVA, GO, rGO and rGO–PVA nanocomposites have been discussed from optical spectrum analysis. The visual structures of the GO, rGO and rGO–PVA nanocomposites are observed from FESEM study. The electric modulus M*(ɷ) formalism used in the analysis enabled us to distinguish and separate the relaxation processes, dominated by marked conductivity in the e*(ɷ) representation. In the ceramics studies, the relaxation times are thermally activated and the dipole process has a clearly non-Debye behaviour. The relaxation process is described with the use of the activation energy of approximately EA = 0.12 eV and the characteristic relaxation time, τ0 = 2.07 × 10–7 s. The dielectric property of the nanocomposite (rGO–PVA) is studied in zero magnetic field and in magnetic field (H) up to 1.2 T. From these data, magnetodielectric effects are obtained as the variation of real (e′) and imaginary (e″) parts of complex dielectric constant with H at some frequencies. In our study at 100 kHz for the increase of H from zero to 1 T e′ decreases by 2.5% in rGO–PVA. This fact is indicative of the interaction between rGO filler particles and PVA polymer chains.