Effect of coupling agents on the dielectric properties and energy storage of Ba_0.5Sr_0.5TiO₃/P(VDF-CTFE) nanocomposites

Dielectric materials with high electric energy density and low dielectric loss are critical for electric applications in modern electronic and electrical power systems. To obtain desirable dielectric properties and energy storage, nanocomposites using Ba_0.5Sr_0.5TiO₃ (BST) as the filler and poly(vinylidene fluoride-chlorotrifluoroethylene) as the matrix material are prepared with a uniform microstructure by using a newly developed process that combines the bridge-linked action of a coupling agent, solution casting, and a hot-pressing method. When a proper amount of coupling agent is used to modify the surface of the nanoparticles, the composite exhibits a higher dielectric constant and a more uniform microstructure. A dielectric constant of 95, dielectric loss of 0.25, and energy density of 2.7 J/cm³ is obtained in the nanocomposite with 30 vol.% of BST and 15 wt.% of coupling agent. The results suggest that the energy storage ability of the composites could be improved by the surface modification of the fillers and from the interface compatibility between the fillers and the polymer matrix.