Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride‐hexafluoropropylene [P(VDF‐HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis loop, is employed as the polymer matrix. Highly dispersive Ba _0.6 Sr _0.4 TiO ₃ (BST) nanoparticles with an average particle size of 12.1 nm are utilised to improve the polarisation of the blend film without sacrificing the dielectric strength. Uniform nanocomposite films with high flexibility and excellent energy‐storage performance are obtained. Especially, due to the optimisation of both polymer matrix and fillers, the BST modified P(VDF‐HFP)/PMMA blend films show improved breakdown strength and depressed energy loss, which leads to an enhanced energy density of 10.3 J/cm ³ at 378 kV/mm.

Large deformability and high sensitivity is difficult to be realized simultaneously in flexible sensors. Herein, taking advantage of the high permittivity and highly active surfaces of the ultrasmall barium titanate nanoparticles (BT NPs) and the high stretchability of the p(BA‐GMA) elastomer matrix, we propose a high‐performance soft stretchable sensor. The addition of the ultrasmall BT NPs can not only increase the permittivity and capacitance of polyacrylate‐matrix composite dielectric material to obtain a high sensitivity, but also basically maintains the excellent mechanical properties of the polymer matrix. The dielectric constants of the composite films increase from 5.68 to 13.13 at 10 kHz with the increase of BT NPs content from 0 to 15 vol.%, which results in a high capacitance of 236.16 pF for 15 vol.% BT/p(BA‐GMA) sensor. Combining the high permittivity and the large deformability (a maximal deformation of 87.2%), the 15 vol.% BT/p(BA‐GMA) sensor has high sensitivity and shows high linearity and stable output even if under dynamic measurement. The dual‐mode sensor that utilizes the orthogonality of capacitance‐resistance is designed, which shows excellent performance in monitoring human body movements and noncontact measurement. The results present that the BT/p(BA‐GMA)‐based sensor has high stability and reliability not exceed 65°C, which can meet the application requirements in dynamic monitoring. image

BaTiO₃ (BTO) nanoparticles (NPs) with controlled particle sizes of 2.8, 4.5 and 8.1 nm and large-scale size uniformity are fabricated. The structure and polarization switching behaviour of the 4.5 nm BTO NPs are investigated. Structural analysis using the atomic pair distribution function (PDF) technique confirms that the particles are non-centrosymmetric at room temperature, and reveals that the ferroelectric distortions are spatially coherent. With increasing temperature, declined ferroelectric features and responses are observed by Raman scattering and second harmonic generation (SHG), suggesting a diffuse phase transition. After self-assembly into compact thin films, selectively written and read electric polarization of the nanocrystals show direct evidence for the presence of ferroelectricity, demonstrating that the local spatial coherent asymmetric nanoparticles with detectable Ti distortion can lead to sufficient macroscopic polarization in the 4.5 nm BTO NP aggregate. The results indicate that these ultrafine ferroelectric NPs are promising candidate materials for the fabrication of high-density ferroelectric memory devices.