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The topological features of the formation of (Co.sub.40Fe.sub.40B.sub.20).sub.15(LiNbO.sub.3).sub.85 composite films deposited by ion-beam method on a metal electrode Cr/Cu/Cr has been investigated. The presence of a dielectric layer between the upper Cr layer and the CoFe-LiNbO.sub.3 film with a thickness of d.sub.ox [almost equal to] 15 nm has been established. The difference in the size of granules near the amorphous layer and in the volume of the film has been shown. A model of the formation of (Co.sub.40Fe.sub.40B.sub.20).sub.x (LiNbO.sub.3).sub.100 -.sub.x nanocomposite film at the initial stage of growth has been proposed. It has been shown that the formation of [alpha]-LiNbO.sub.3 layer on the chrome metal film surface is possible with the realization of island and layer-by-layer growth mechanisms for various phases of the composite.

Due to the appealing piezoelectric, pyroelectric, and ferroelectric (FE) properties, poly(vinylidene fluoride) (PVDF)-based dielectric polymers have been attracting great attention from both the academic and industrial communities. Depending on the molecular structure and the processing method, PVDF-based dielectric polymers can exhibit rich dielectric polarisation behaviours covering normal FE, relaxor FE, anti-FE-like and linear dielectric responses, which enables a wide spectrum of application fields such as non-volatile memories, piezoelectric and pyroelectric sensors, actuators, electrocaloric refrigeration, and film capacitors. In this study, the authors first briefly introduce the current practical/promising applications of PVDF-based dielectric polymers, and the corresponding optimum dielectric polarisation behaviour and crystal structure are proposed accordingly. The chemical synthesis and modification strategies for obtaining various fluoropolymers beyond PVDF homopolymer are then summarised with an emphasis on the relationship between the molecular structure and the dielectric polarisation behaviour. In addition, the effect of processing methods on the crystal structure and dielectric properties of the PVDF-based polymers is discussed. Finally, some newly developed processing techniques applicable to PVDF-based polymers are described.

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.

A new family of tunable microwave dielectrics with unparalleled performance at frequencies up to 125 GHz at room temperature has been created, using dimensionality to add and control a local ferroelectric instability in a system with exceptionally low dielectric loss. Microwave-proof insulators Tunable dielectric materials are valuable components for complex microwave circuitry, yet such materials tend to suffer losses when operated at microwave frequencies owing to intrinsic defects in their structures. Che-Hui Lee and colleagues have selected a family of dielectrics known to exhibit exceptionally low loss, and now show how these materials can be engineered to boost their tunability and attain levels of performance that rival all known tunable microwave dielectrics. The miniaturization and integration of frequency-agile microwave circuits—relevant to electronically tunable filters, antennas, resonators and phase shifters—with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field 1 . Appropriate systems such as Ba x Sr 1− x TiO 3 have a paraelectric–ferroelectric transition just below ambient temperature, providing high tunability 1 , 2 , 3 . Unfortunately, such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss—Sr n +1 Ti n O 3 n +1 phases 4 , 5 —in which (SrO) 2 crystallographic shear 6 , 7 planes provide an alternative to the formation of point defects for accommodating non-stoichiometry 8 , 9 . Here we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability 10 in biaxially strained Sr n +1 Ti n O 3 n +1 phases with n  ≥ 3 at frequencies up to 125 GHz. In contrast to traditional methods of modifying ferroelectrics—doping 1 , 2 , 3 , 11 , 12 or strain 13 , 14 , 15 , 16 —in this unique system an increase in the separation between the (SrO) 2 planes, which can be achieved by changing n , bolsters the local ferroelectric instability. This new control parameter, n , can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics 3 .

The resonant modes of plasmonic nanoparticle structures made of gold or silver endow them with an ability to manipulate light at the nanoscale. However, owing to the high light losses caused by metals at optical wavelengths, only a small fraction of plasmonics applications have been realized. Kuznetsov et al. review how high-index dielectric nanoparticles can offer a substitute for these metals, providing a highly flexible and low-loss route to the manipulation of light at the nanoscale. Science , this issue p. 10.1126/science.aag2472 Rapid progress in nanophotonics is driven by the ability of optically resonant nanostructures to enhance near-field effects controlling far-field scattering through intermodal interference. A majority of such effects are usually associated with plasmonic nanostructures. Recently, a new branch of nanophotonics has emerged that seeks to manipulate the strong, optically induced electric and magnetic Mie resonances in dielectric nanoparticles with high refractive index. In the design of optical nanoantennas and metasurfaces, dielectric nanoparticles offer the opportunity for reducing dissipative losses and achieving large resonant enhancement of both electric and magnetic fields. We review this rapidly developing field and demonstrate that the magnetic response of dielectric nanostructures can lead to novel physical effects and applications.

A transmissive single-layer Huygens unit cell based on induced magnetism is proposed to design low-profile and multi-focus metasurface. The Huygens unit cell consists of a pair of antisymmetric metal elements and a dielectric substrate with only 1.2mm thickness ([[lambda].sub.0]/6.8 at 37GHz). The surface currents flowing in the opposite directions form the circulating electric currents to induce the magnetic currents orthogonal to the electric currents. The full coverage of 2n phase is achieved through optimizing the parameters of the metal elements, which solves the problem of the incomplete phase coverage caused by layer number reduction. With Holographic theory, the compensating phase distribution on the metasurface is calculated. The incident plane wave can be converged to designated points in any desired fashion including focal number, location, and intensity distribution, which exhibits outstanding manipulation capability. As the simulations and measured results show, the designed metasurface can achieve good multi-focus focusing characteristics. The focusing efficiency at the center frequency is 43.78%, and the relative bandwidth with 20% focusing efficiency exceeds 20%. The designed metasurface has the advantages of low profile, simple processing, and high efficiency, which has a wide range of application prospects in the fields of millimeter wave imaging, biomedical diagnosis and detection.

HighlightsA general method was developed to fabricate a series of honeycomb-like N-doped nanocarbons (3D M–NxC) doped with metal single atoms (Mn, Fe, Co, Cu, or Ni) with a high yield.The intrinsic dielectric properties of 3D M–NxC were identified for the first time at the atomic-level, revealing that the introduction of metal single atoms greatly increases both conductive loss and polarization loss.3D Mn–NC exhibited high-performance electromagnetic wave absorption at a low filler loading of 10 wt% outperforming most reported absorbers.Atomically dispersed metals on N-doped carbon supports (M–NxCs) have great potential applications in various fields. However, a precise understanding of the definitive relationship between the configuration of metal single atoms and the dielectric loss properties of M–NxCs at the atomic-level is still lacking. Herein, we report a general approach to synthesize a series of three-dimensional (3D) honeycomb-like M–NxC (M = Mn, Fe, Co, Cu, or Ni) containing metal single atoms. Experimental results indicate that 3D M–NxCs exhibit a greatly enhanced dielectric loss compared with that of the NC matrix. Theoretical calculations demonstrate that the density of states of the d orbitals near the Fermi level is significantly increased and additional electrical dipoles are induced due to the destruction of the symmetry of the local microstructure, which enhances conductive loss and dipolar polarization loss of 3D M–NxCs, respectively. Consequently, these 3D M–NxCs exhibit excellent electromagnetic wave absorption properties, outperforming the most commonly reported absorbers. This study systematically explains the mechanism of dielectric loss at the atomic level for the first time and is of significance to the rational design of high-efficiency electromagnetic wave absorbing materials containing metal single atoms.

The dielectric properties of polymers play a pivotal role in the development of advanced materials for energy storage, electronics, and insulation. This review comprehensively explores the critical relationship between polymer chain conformation, nanostructure, and dielectric properties, focusing on parameters such as dielectric constant, dielectric loss, and dielectric breakdown strength. It highlights how factors like chain rigidity, free volume, molecular alignment, and interfacial effects significantly influence dielectric performance. Special emphasis is placed on the impact of nanofillers, molecular weight, crystallinity, and multilayer structures in optimizing these properties. By synthesizing findings from recent experimental and theoretical studies, this review identifies strategies to enhance energy efficiency, reliability, and mechanical stability of polymer-based dielectrics. We also delve into techniques such as electrostatic force microscopy (EFM) and focused ion beam (FIB) milling for characterizing breakdown mechanisms, offering insights into molecular design for next-generation high-performance polymers. Despite considerable progress, critical challenges such as achieving an optimal balance between dielectric permittivity and breakdown strength, understanding nanoscale interfacial phenomena, and scaling these materials for industrial applications persist. These gaps can be addressed by systematic structure–property relations, advanced processing techniques, and environmental studies.

The optimized concentration of SF[sub.6] gas is the key to maintaining a good insulation performance by GIS equipment. The precise measurements of the SF[sub.6] concentration and decomposition byproducts could be used to indicate the remaining GIS insulation level during long-term operations. In this paper, a finite-element simulation model was created to investigate the SF[sub.6] gas decomposition and diffusion dynamics. A theoretical analysis and simulation of the overheating fault, i.e., the contact between the GIS disconnect switches, were carried out, followed by an estimation of the SF[sub.6] decomposition and diffusion characteristics caused by the local heating faults, based on the calculated flow velocity field and temperature field.