Flexible and multifunctional P(VDF-TrFE)/BT-BMT polymer composite films: Realizing high piezoelectric performance and electrocaloric effect

Abstract

In the era of unprecedented advancement of portable electronics, the utilization of multifunctional materials that enable integration of functionalities, hold great promise since they not only reduce size and weight but also curtail energy consumption of the system. In this regard, this study focused on the development of polyvinylidene fluoride (PVDF)-based polymer composites and achieved excellent piezoelectric performance along with enhanced dielectric, ferroelectric and electrocaloric response. Novel flexible polymer composite films composed of P(VDF-TrFE) 55/45 polymer and BT-BMT (BaTiO<inf>3</inf>-0.2Bi(Mg<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf>) oxide filler particles were fabricated using cost-effective solution-casting method. The inclusion of BT-BMT fillers promoted ferroelectric β-phase formation, confirmed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopy studies. The dielectric permittivity enhanced considerably with the incorporation of filler particles, while the dielectric loss remained low. An excellent piezoelectric coefficient, |d<inf>33</inf>| ∼41 pC/N was achieved in the optimal composite (5 wt% BT-BMT), which was nearly 58 % higher than that obtained in the pure copolymer (|d<inf>33</inf>| ∼26 pC/N). Furthermore, an improved electrocaloric performance in terms of electrocaloric temperature change (ΔT) and electrocaloric strength was noted. A ΔT ∼3.15 °C was achieved in the optimal composite film at a modest electric field of 60 MV/m. Additionally, the investigation of microscale piezoelectric and mechanical responses revealed a correlation with the macroscale properties and suggested a complex interplay of interphase effects (filler–polymer interface; crystalline–amorphous interface) in the films. Thus, this work highlights the significance of the BT-BMT fillers in enhancing prominent functional properties in the P(VDF-TrFE)/BT-BMT polymer composite films, thereby rendering them suitable for multifunctional flexible devices.