Enhanced dielectric tunability of Ba_0.6Sr_0.4TiO₃/Poly(vinylidene fluoride) composites via interface modification by silane coupling agent

(Ba_0.6Sr_0.4)TiO₃ (BST)/poly(vinylidene fluoride) (PVDF) composites were fabricated by tape casting using aminopropyl triethoxy silane (KH550) modified BST particles and PVDF matrix polymer. Effects of the KH550 mass fraction on the microstructure and dielectric properties of BST/PVDF composites were investigated. The results show that the surface of BST particles was covered by silane coupling agent. The KH550 not only can connect with the surface of BST particles by dehydration reaction but also can form hydrogen bond with PVDF. The relative permittivity raised in the first stage (i.e., 0 wt%-4 wt%), then decreased as the concentration of KH550 increasing, while the loss tangent exhibits a trend opposite to that of the dielectric constant. KH550 will improve the dielectric tunability and energy storage density of the BST/PVDF composites. A threshold bias was observed in the plot of the dielectric tunability vs. applied electric DC field. BST/PVDF composites with KH550 show the high dielectric tunability (>78%). The maximum dielectric tunability of 95.2% under a low electric bias of 40 kV/mm, and the highest energy storage density of 5.28 J/cm³ were obtained for BST/PVDF composites with 4 wt% KH550.