Ferroelectric barium titanate nanocubes as capacitive building blocks for energy storage applications

Highly uniform polymer-ceramic nanocomposite films with high energy density values were fabricated by exploiting the unique ability of monodomain, nonaggregated BaTiO₃ colloidal nanocrystals to function as capacitive building blocks when dispersed into a weakly interacting dielectric matrix. Monodisperse, surface-functionalized ferroelectric 15 nm BaTiO₃ nanoparticles have been selectively incorporated with a high packing density into poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) leading to the formation of biphasic BaTiO₃-P(VDF-HFP) nanocomposite films. A systematic investigation of the electrical properties of the nanocomposites by electrostatic force microscopy and conventional dielectric measurements reveals that polymer-ceramic film capacitor structures exhibit a ferroelectric relaxor-type behavior with an increased intrinsic energy density. The composite containing 7% BaTiO₃ nanocrystals displays a high permittivity (ε = 21) and a relatively high energy density (E = 4.66 J/cm³) at 150 MV/m, which is 166% higher than that of the neat polymer and exceeds the values reported in the literature for polymer-ceramic nanocomposites containing a similar amount of nanoparticle fillers. The easy processing and electrical properties of the polymer-ceramic nanocomposites make them suitable for implementation in pulse power capacitors, high power systems and other energy storage applications.