Modulation of Electrical Characteristics of Polymer–Ceramic–Graphene Hybrid Composite for Piezoelectric Energy Harvesting

Abstract

The use of lead-based ceramics to enhance the piezoelectricity of poly(vinylidene fluoride) (PVDF) is the primary challenge toward nontoxic flexible piezoelectric devices. 0.67BiFeO3-0.33BaTiO3 (BF33BT) is one of the lead-free piezoceramics with high-temperature stability and comparable piezoelectric characteristics to existing lead-based piezoceramics. The work represents PVDF–BF33BT two-phase and PVDF–BF33BT–graphene oxide (GO) three-phase composites with detailed analysis of the dielectric, ferroelectric, and piezoelectric characterizations. Solvent-casting followed by the hot-pressing technique improves the electroactive β-phase of ≥60% in the composites. With BF33BT and GO loading, the dielectric constant and loss tangent increase; however, there is an abrupt rise at the threshold GO concentration of 0.08 wt %. The three-phase composite with 40 wt % BF33BT and 0.08 wt % GO records a dielectric constant of 303 and a loss tangent of 0.68. The harvester out of the same composition achieves a piezoelectric strain constant of 9 pC·N–1, an open-circuit voltage of ∼3.9 V, and a short-circuit current of 1.3 μA. The feasibility of the harvester was tested by powering a calculator by charging a 2.2 μF capacitor after rectification. The recoverable energy density also improves seven times, indicating that the PVDF–BF33BT–GO composite is preferable for piezoelectric and energy storage applications.