Synergistic effect of graphene on dielectric and piezoelectric characteristic of PVDF-(BZT-BCT) composite for energy harvesting applications

Piezoelectric energy harvester has attracted considerable attention as an independent power source for applications in biocompatible, implantable, and flexible electronic devices. However, the lacuna of getting enhanced piezoelectric response from flexible lead-free polymer-based composite persists in this field. Here, we present a detailed study on the electrical characteristics such as dielectric, ferroelectric, and piezoelectric properties of (PVDF)-[0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3]-graphene oxide (GO) three-phase composite films synthesized by solvent-casting followed by a hot pressing method. Structural investigations reveal that the fraction of beta-phase of PVDF in all the composites is more than 65%. The dielectric constant of the composite increases up to the threshold value (0.16 wt% for GO and 0.08 wt% for rGO), and further loading causes a decrease in the dielectric constant. The composite with GO concentration of 0.16 wt% (G-0.16) shows a dielectric constant of 25.6 with a loss tangent of 0.0498. In contrast, composite with reduced graphene oxide (rGO) concentration of 0.08 wt% (R-0.08) are 24.3 and 0.0681, respectively, at 1 kHz. Remnant polarization and d(33) value of G-0.16 are 0.012 mu C cm(-2) and 11 pC N-1, respectively, which are six times and four times more than pure PVDF. The piezoelectric harvester from G-0.16 produces an open-circuit voltage of similar to 4 V and a short-circuit current of similar to 1.6 mu A with simple hand tapping, which is the highest among the compositions, makes it a suitable candidate for piezoelectric energy harvesting applications.