Interfacial effects on ferroelectric and dielectric properties of GO reinforced free-standing and flexible PVDF/ZnO composite membranes: Bias dependent impedance spectroscopy

Flexible membranes with attractive ferroelectric and dielectric properties are promising for numerous technological devices, such as, energy storage and harvesting devices, sensors etc. Here we report the development of conducting nanofiller containing inorganic semiconductor and organic polymer based tri-phase composite membranes and demonstrate their ferroelectric and frequency dependent dielectric characteristics. The graphene oxide (GO) nanosheet reinforced free-standing, flexible and beta-phase abundant PVDF/ZnO composite membranes are fabricated by simple, low-cost and scalable chemical method. The ferroelectric properties of the PVDF polymer based composite membranes are modified through incorporation of small amount of GO and ZnO without sacrificing the mechanical flexibility as evidenced by electrical polarization characteristics. The ferroelectric polarization for PVDF/ZnO and PVDF/ZnO/GO membranes are respectively 15.98 and 14.14 mC/cm(2) at only 15 kV/cm electric field which are distinctly superior than PVDF-copolymer and PVDF-perovskite based composites as reported recently. Furthermore, as per our knowledge for the first time we have studied the effects of external electric field on dielectric relaxation times originating from the electrical responses from core grains and grain-boundary or interfaces by using dc bias dependent impedance spectroscopy. The modulation in dielectric permittivity of the composite membranes is attributed to the formation of complete beta-crystalline phase in PVDF/ZnO/GO membranes and introduction of active interfaces facilitating induced electrical polarization. These studies provide significant insight into the interfacial effects on the electrical transport, ferroelectric and dielectric properties of tri-phase PVDF/ZnO/GO polymer membrane, an emerging energy material. (C) 2020 Elsevier B.V. All rights reserved.