Enhanced dielectric properties and suppressed leakage current density of PVDF composites flexible film through small loading of submicron Ba_0.7Sr_0.3TiO₃ crystallites

Ba_0.7Sr_0.3TiO₃ (BST) crystallites prepared by sol–gel technique are incorporated into poly(vinylidene fluoride) PVDF matrix by solution casting technique. Cuboid shape of crystallite has been confirmed by high resolution transmission electron microscopy. PVDF composite films exhibit high dielectric constant and very low leakage current density. The dielectric constant ~22 (at 1 kHz) has been obtained for composites containing 11 vol% of BST crystallite; which is ~3 times higher than the dielectric constant of the pure PVDF (~7.9). Moreover, the leakage current density with same loading of BST crystallite increased only by one order (i.e. 10⁻⁷Amp/cm² for pure PVDF to 10⁻⁶Amp/cm²). The observed value of leakage current density is very small as compared to earlier reports. The dielectric loss was found to be 0.02–0.03 at 1 kHz, which is also very small. The improved dielectric behavior is attributed to the improved interface between PVDF and BST crystallite and, the suppressed leakage current density might be arising due to smaller conducting pathways at interface.