Ceramic capacitors with upper operating temperatures far beyond 200°C are essential for high-temperature electronics used in deep oil drilling, aviation, automotive industry and so on. Recent advances in existing lead-free dielectrics for potential high-temperature capacitor applications are reviewed and grouped into three categories according to the parent component of the solid solution. Their desirable temperature stabilities were summarised comprehensively. However, there are still some limitations in the current research, such as achieving low loss in a wide temperature range and maintaining stable dielectric properties with different frequencies or at different voltages. Furthermore, the successful implementation of multilayer ceramic capacitors is one of the biggest challenges, which will have far-reaching impacts on the realisation of high-temperature capacitor application in the future.

The attractive dielectric poly(vinylidene fluoride) (PVDF) and its copolymers are well confirmed possessing the highest electroactive response including dielectric constant, piezoelectric and ferroelectric effects, which have increasingly wide range of applications such as in energy transfer, energy generation and storage, monitoring and control, and include the development of capacitors, sensors, actuators and so on. In this study, by clarifying the reliability of dielectric performances on their crystal phase structure of various PVDF polymers, the different physical and chemical fabricating ways to achieve different forms of PVDF samples such as linear polymers, ferroelectrics, and relaxor ferroelectrics were identified and quantified. In addition, many recent advances in the PVDF-based polymer dielectrics and some developed applications of these polymers are presented, which gives a reference in academic and engineering area to select an appropriate PVDF series dielectric polymer.

Dielectric materials with excellent energy storage capability at elevated temperatures are critical to meet the increasing demand of electrical energy storage and power conditioning at extreme conditions such as hybrid electric vehicles, underground oil industries and aerospace systems. This review study summarises the important aspects and recent advances in the development of nanostructured dielectric materials including ceramics, polymers and polymer composites for high-temperature capacitor applications. The advantages and limitations of current dielectric materials are discussed and analysed. Ongoing research strategies to suppress the conduction loss and optimise the high-temperature capacitive performance of dielectrics have been highlighted. A summary and outlook will conclude this review.

Flexible polymer-matrix nanodielectrics have recently been attracting more attention in the fields of frontier research internationally since the beginning of the 21st century. It would accelerate a technical reformation for the applications in new energies, bioscience and biomedical engineering, artificial intelligence, electronic skin, wearable electronic clothing, Internet of things, and electrical insulation. This review summarises the recent development and achievements of nanodielectrics, including space charge suppression, high energy density storage, partial discharge resistance, non-linear field grading properties, high thermal conductivity, and future applications in biomedical area. Special attention is given to two representative interface models that are the Lewis's diffusion electrical double-layer model and Tanaka's multi-core model. At last, some issues related to the technology of nanodielectrics have also been discussed.

The epoxy resin was filled with nano-BN, surface treated, and untreated nano-SiO₂. Measurements of dielectric spectroscopy cover the range of frequency from 10⁻² to 10⁵ Hz and will relate to the hydration of samples. It was observed from the results that permittivity of pure epoxy was strongly affected by the water absorptions and a bit of temperature. Then it will allow us to extract the influence of water absorption on dielectric properties and proposed a relatively reliable method by using Monte-Carlo simulation to estimate the average thickness of water shell or related relaxation peak of epoxy nanocomposites with spherical particles. At the end, the authors experimentally demonstrated the existence of two layer structure of water shell and concluded that surface treatment is able to reduce the water uptake, however, no obvious impact on modifying its effects on dielectric properties due to the limitation of thickness of tightly bonded layer. The ‘hydrophobic’ performance of BN nanocomposites is much better than silica ones, especially the no formation of water shell around the particles, and may be more suitable for application under environment with humidity.

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_0.6Sr_0.4TiO₃ (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/cm³ at 378 kV/mm.