Quenching induced modified nanoarchitectonics in the dielectric and energy storage behavior of poly (vinylidene fluoride)/Ba_0.7Sr_0.3TiO₃ composites thick films

Free-standing flexible poly(vinylidene fluoride)-barium strontium titanate (PVDF-BST) composite films loaded with 5 vol% of Ba_0.7Sr_0.3TiO₃ submicronic particles have been synthesized. The synthesized PVDF-BST composite film was quenched in ice water as quenching strongly affects its crystalline phase, dielectric and energy storage behavior. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) studies confirmed that quenching leads to the evolution of the β-phase of PVDF in the PVDF-BST composite films. At 1 kHz, the dielectric constant of the quenched film is ~ 17, which is higher than that of the unquenched film, i.e. ~ 15. At 460 kV/cm, the energy density of the quenched film is 2.5 times higher (~ 4.8 J/cc) as compared to the unquenched film (1.9 J/cc). Significant improvement in the dielectric constant and energy density is attributed to the formation of β-phase of PVDF in PVDF-BST composite film. Mechanism for β-phase formation by quenching at low temperatures has also been suggested.