Ferroelectric-relaxor behavior of Ba(Zr0.3Ti0.7)O3 nanofibers (BZT NF) with a large aspect ratio were prepared via electrospinning and surface modified by PVP as dielectric fillers. The nanocomposite flexible films based on surface modified BZT NF and polyvinylidene fluoride (PVDF) were fabricated via a solution casting. The results show that the surface-modified BZT NF fillers are highly dispersed and well integrated in the PVDF nanocomposites. The nanocomposites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified BZT NF. The polymer nanocomposites maintain a relatively high breakdown strength, which is favorable for enhancing energy storage density in the nanocomposites. The nanocomposite containing of 2.5 vol. % of PVP modified BZT NF exhibits energy density as high as 6.3 J/cm3 at 3800 kV/cm, which is more than doubled that of the pure PVDF of 2.8 J/cm3 at 4000 kV/cm. Such significant enhancement could be attributed to the combined effects of the surface modification and large aspect ratio of the BZT NF. This work may provide a route for using the surface modified ferroelectric-relaxor behavior of ceramic nanofibers to enhance the dielectric energy density in ceramic-polymer nanocomposites.

Schematic diagrams of the fabrication of F-BST NF/PVDF nanocomposites.

Ceramic-polymer nanocomposites, consisting of surface hydroxylated cube-shaped Ba 0.6 Sr 0.4 TiO 3 nanoparticles (BST-NPs) as fillers and poly(vinylidenefluoride) (PVDF) as matrix, have been fabricated by using a solution casting method. The nanocomposites exhibited increased dielectric constant and improved breakdown strength. Dielectric constants of the nanocomposite with surface hydroxylated BST-NPs (BST-NPs-OH) were higher as compared with those of their untreated BST-NPs composites. The sample with 40 vol % BST-NPs-OH had a dielectric constant of 36 (1 kHz). Different theoretical models have been employed to predict the dielectric constants of the nanocomposites, in order to compare with the experimental data. The BST-NPs-OH/PVDF composites also exhibited higher breakdown strength than their BST-NP/PVDF counterparts. A maximal energy density of 3.9 J/cm 3 was achieved in the composite with 5 vol % BST-NPs-OH. This hydroxylation strategy could be used as a reference to develop ceramic-polymer composite materials with enhanced dielectric properties and energy storage densities.

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