Modulation in polymer properties in pvdf/bczt composites with ceramic content and their energy density.

Abstract

The lead‐free 0.5((Ba0.7Ca0.3)TiO3)‐0.5(Ba(Zr0.2Ti0.8))O3(BCZT) piezoceramics were synthesized using sol‐gel method. The Rietveld analysis of X‐ray diffraction (XRD) data and differential scanning calorimetry (DSC) studies of as‐synthesized BCZT powder suggests the co‐existence of ferroelectric orthorhombic (O) and tetragonal (T) phases at room temperature (RT). The value of curie temperature (TT‐C) as depicted from DSC and dielectric studies was found to be ≈ 110°C. The BCZT ceramic particles were dispersed in the polyvinylidene fluoride (PVDF) matrix, an electroactive polymer with great ferro/piezoelectric response in its distinct β and γ phases, to form ferroelectric ceramic‐polymer composites for their applications in flexible energy storage capacitors. The present work reports the Fourier‐transform infrared spectroscopy (FTIR), XRD, dielectric, ferroelectric, and energy density properties of PVDF/BCZT composite films having different wt% of BCZT content fabricated by the solution‐cast technique. The FTIR and XRD studies depict the γ‐PVDF and pure BCZT phases in composite films. The dielectric studies estimated the relative permittivity (εr) of a composite film with 50 wt% of BCZT content to be ≈ 31 (at 120 Hz) which was about three times as compared with that of pure PVDF. The dielectric loss (tan δ) was maximum ≈ 0.15 (at 120 Hz) for 50 wt% BCZT composition. The ferroelectric studies and energy storage calculations showed that the value of remnant polarization (Pr), coercive field (Ec) and energy storage density (W) attain the maximum value of 0.63 μC/cm², 35.22 kV/cm, and 70.46 mJ/cm³, respectively for the film sample having 40 wt% BCZT content. The maximum energy storage efficiency, η (%) is calculated to be ≈ 60 for 50 wt% BCZT composition. The results indicated that the incorporation of BCZT particles in the PVDF matrix improved the overall polarization (polar and interfacial) which enhance the electric properties of composite films. The ferroelectric studies with temperature revealed the PVDF/BCZT composition‐dependent polymer or ceramic dominance in the behavior of composite films. With the maximum value of relative permittivity (εr) and energy storage efficiency (η), the PVDF/BCZT composition with 50 wt% of BCZT content has been optimized for applications in flexible energy storage capacitors.