Re-evaluation of the Energy Density Properties of VDF Ferroelectric Thin-Film Capacitors

Large dielectric constants and small remanent polarization of the relaxor-ferroelectric (RFE) polymers are favored for energy-harvesting applications. Here, the energy harvesting of RFE thin films of vinylidene fluoride (VDF)-based terpolymers were re-evaluated. VDF-based terpolymers with trifluoroethylene (TrFE) and chlorofluoroethylene (CFE), CFE terpolymer, and those with TrFE and chlorotrifluoroethylene were used. Thermally annealed CFE terpolymer exhibited an energy density of 8.3 J cm(-3) and an energy efficiency of 82% at a field of 280 MV m(-1). The high-energy efficiency was related to the narrow bipolar hysteresis of displacement (D)-electric field (E) of the CFE terpolymer film. This narrow D-E hysteresis was a sum of the unipolar hysteresis directed toward the positive electric field region and that toward the negative electric field region, which suggested antiferroelectric-like behavior.