Effect of interfacial layers on the temperature-dependent dielectric and impedance behavior of flexible PVDF-BST nanocomposite thick films

Abstract

High energy storage performance of polymer-ceramic nanocomposites at elevated temperatures (room temperature to 100 °C) becomes unstable because of thermally unstable dielectric behavior (permittivity and loss tangent). Therefore, the present work describes the experimental and analytical investigation of the temperature-dependent dielectric behavior, AC conductivity, and impedance of flexible poly(vinylidene difluoride) (PVDF)-Ba0.8Sr0.2TiO3 (BST) nanocomposite thick films. An increase in the dielectric constant and a decrease in the loss tangent is found with an increase in the loading of BST nanoparticles in the nanocomposite thick films. The highest dielectric constant, approximately 25, and the lowest loss tangent, approximately 0.03, are observed for 10 wt% BST–loaded PVDF-BST nanocomposite at 1 kHz; the dielectric constant and the loss tangent increase to approximately 93 and approximately 1.64, respectively, at 150 °C. The dielectric constant and the loss tangent of all the PVDF-BST nanocomposites are thermally stable up to 70 °C, and then increase with further increase of the temperature. A phenomenological model is proposed to explain the experimentally observed behavior, which might be attributed to the thermally induced translational motion in the polymeric chains of PVDF, the motion of ions, and the migration of space charge in the interfacial layer of the PVDF matrix and BST nanoparticles.