Significantly Enhanced Dielectric Behavior of Polyvinylidene Fluoride-Barium Strontium Titanate Flexible Nanocomposite Thick Films: Role of Electric Field-Induced Effects

The polyvinylidene fluoride (PVDF)-0.05Ba_0.8Sr_0.2TiO₃ (BST) nanocomposite (0.05 is the fractional weight of BST) facile thick films of thickness ~100 μm have been synthesized by tape-casting. The synthesized films are exposed to an electric field of 22 kV/mm (for different time durations, 0 min, 40 min, 50 min, and 60 min) to investigate the electric field-induced effects on dielectric and structural properties of nanocomposite thick films. Structural studies have shown that the electric field increases the β phase of PVDF in PVDF-BST nanocomposites. The most prominent effect of the applied electric field is observed in the dielectric behavior of the nanocomposite thick films. The film exposed to the electric field for 60 min has the highest dielectric constant (~25) and very low tangent loss (~0.02) at 1 kHz, whereas the unexposed film of nanocomposite has a dielectric constant of ~15 and tangent loss (~0.03). The approximated Debye relaxation theory has been used to understand the correlation between dielectric and structural observations. Analysis confirms the duration of exposure to the electric field enhances the β-phase, which causes the increase in the density of dipoles. The enhanced dielectric performance is attributed to the increased dipolar density due to modification in the structural and interfacial behavior as well as molecular motion of the dipoles in the polymeric chain.