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Showing papers on "Dielectric published in 2020"


Journal ArticleDOI
17 Jan 2020-Science
TL;DR: This work implements a new physical mechanism for suppressing radiative losses of individual nanoscale resonators to engineer special modes with high quality factors: optical bound states in the continuum (BICs), and demonstrates that an individual subwavelength dielectric resonator hosting a BIC mode can boost nonlinear effects increasing second-harmonic generation efficiency.
Abstract: Subwavelength optical resonators made of high-index dielectric materials provide efficient ways to manipulate light at the nanoscale through mode interferences and enhancement of both electric and magnetic fields. Such Mie-resonant dielectric structures have low absorption, and their functionalities are limited predominantly by radiative losses. We implement a new physical mechanism for suppressing radiative losses of individual nanoscale resonators to engineer special modes with high quality factors: optical bound states in the continuum (BICs). We demonstrate that an individual subwavelength dielectric resonator hosting a BIC mode can boost nonlinear effects increasing second-harmonic generation efficiency. Our work suggests a route to use subwavelength high-index dielectric resonators for a strong enhancement of light-matter interactions with applications to nonlinear optics, nanoscale lasers, quantum photonics, and sensors.

543 citations


Journal ArticleDOI
Mengqiu Huang1, Lei Wang1, Ke Pei1, Wenbin You1, Xuefeng Yu1, Zhengchen Wu1, Renchao Che1 
01 Apr 2020-Small
TL;DR: Carbonized Co@NC composites possess the following advantages: i) controllable dimension and morphology to balance the electromagnetic properties with evenly charged density distribution; ii) magnetic-carbon composites offer plenty of interfacial polarization and strong magnetic coupling network; iii) a MOF-derived dielectric carbon skeleton provides electronic transportation paths and enhances conductive dissipation
Abstract: Metal-organic framework (MOF) is highly desirable as a functional material owing to its low density, tunable pore size, and diversity of coordination formation, but limited by the poor dielectric properties. Herein, by controlling the solvent and mole ratio of cobalt/linker, multidimension-controllable MOF-derived nitrogen-doped carbon materials exhibit tunable morphology from sheet-, flower-, cube-, dodecahedron- to octahedron-like. Tunable electromagnetic parameters of Co@N-doped carbon composites (Co@NC) can be obtained and the initial MOF precursor determines the distribution of carbon framework and magnetic cobalt nanoparticles. Carbonized Co@NC composites possess the following advantages: i) controllable dimension and morphology to balance the electromagnetic properties with evenly charged density distribution; ii) magnetic-carbon composites offer plenty of interfacial polarization and strong magnetic coupling network; iii) a MOF-derived dielectric carbon skeleton provides electronic transportation paths and enhances conductive dissipation. Surface-mediated magnetic coupling reflects the stray magnetic flux field, which is corroborated by the off-axis electron holography and micro-magnetic simulation. Optimized octadecahedral Co@NC sample exhibits the best microwave absorption (MA) of -53.0 dB at the thickness of 1.8 mm and broad effective frequency from 11.4 to 17.6 GHz (Ku-band). These results pave the way to fabricate high-performance MA materials with balanced electromagnetic distribution and controlled morphology.

305 citations


Journal ArticleDOI
TL;DR: A strategy to increase the breakdown electric field and thus enhance the energy storage density of polycrystalline ceramics by controlling grain orientation is proposed, which is expected to benefit a wide range of applications of dielectrics for which high breakdown strength is required, such as high-voltage capacitors and electrocaloric solid-state cooling devices.
Abstract: Dielectric ceramics are highly desired for electronic systems owing to their fast discharge speed and excellent fatigue resistance. However, the low energy density resulting from the low breakdown electric field leads to inferior volumetric efficiency, which is the main challenge for practical applications of dielectric ceramics. Here, we propose a strategy to increase the breakdown electric field and thus enhance the energy storage density of polycrystalline ceramics by controlling grain orientation. We fabricated high-quality -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics, in which the strain induced by the electric field is substantially lowered, leading to a reduced failure probability and improved Weibull breakdown strength, on the order of 103 MV m−1, an ~65% enhancement compared to their randomly oriented counterparts. The recoverable energy density of -textured NBT-SBT multilayer ceramics is up to 21.5 J cm−3, outperforming state-of-the-art dielectric ceramics. The present research offers a route for designing dielectric ceramics with enhanced breakdown strength, which is expected to benefit a wide range of applications of dielectric ceramics for which high breakdown strength is required, such as high-voltage capacitors and electrocaloric solid-state cooling devices. The energy density of dielectric ceramic capacitors is limited by low breakdown fields. Here, by considering the anisotropy of electrostriction in perovskites, it is shown that -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 ceramics can sustain higher electrical fields and achieve an energy density of 21.5 J cm−3.

283 citations


Journal ArticleDOI
TL;DR: In this article, a high dielectric constant of 1568 ± 15% at an ultra-wide temperature range of 60-600°C was achieved in novel 0.9NBT-0.1LT lead-free ceramics via LiTaO3 modification and composition engineering.

237 citations


Journal ArticleDOI
TL;DR: This work reports that high Wrec of 6.3 J cm-3 with η of 90% can be simultaneously achieved by constructing a room temperature M2–M3 phase boundary in (1-x)AgNbO3-xAgTaO3 solid solution system, and provides a good paradigm for developing new lead-free dielectrics for high-power energy storage applications.
Abstract: Dielectric capacitors with high energy storage density (Wrec) and efficiency (η) are in great demand for high/pulsed power electronic systems, but the state-of-the-art lead-free dielectric materials are facing the challenge of increasing one parameter at the cost of the other. Herein, we report that high Wrec of 6.3 J cm-3 with η of 90% can be simultaneously achieved by constructing a room temperature M2–M3 phase boundary in (1-x)AgNbO3-xAgTaO3 solid solution system. The designed material exhibits high energy storage stability over a wide temperature range of 20–150 °C and excellent cycling reliability up to 106 cycles. All these merits achieved in the studied solid solution are attributed to the unique relaxor antiferroelectric features relevant to the local structure heterogeneity and antiferroelectric ordering, being confirmed by scanning transmission electron microscopy and synchrotron X-ray diffraction. This work provides a good paradigm for developing new lead-free dielectrics for high-power energy storage applications. Dielectric capacitors are widely used in electronic systems but they possess inferior energy density in comparison with other electrochemical energy storage. Here, the authors construct a diffused phase boundary to simultaneously achieve high energy storage density and efficiency in AgNbO3antiferroelectrics.

233 citations




Journal ArticleDOI
TL;DR: It is shown that all-organic composites containing high-electron-affinity molecular semiconductors exhibit excellent capacitive performance at 200 °C, which is crucially important for their successful commercialization and practical application in high-temperature electronics and energy storage devices.
Abstract: Dielectric polymers for electrostatic energy storage suffer from low energy density and poor efficiency at elevated temperatures, which constrains their use in the harsh-environment electronic devices, circuits, and systems. Although incorporating insulating, inorganic nanostructures into dielectric polymers promotes the temperature capability, scalable fabrication of high-quality nanocomposite films remains a formidable challenge. Here, we report an all-organic composite comprising dielectric polymers blended with high-electron-affinity molecular semiconductors that exhibits concurrent high energy density (3.0 J cm−3) and high discharge efficiency (90%) up to 200 °C, far outperforming the existing dielectric polymers and polymer nanocomposites. We demonstrate that molecular semiconductors immobilize free electrons via strong electrostatic attraction and impede electric charge injection and transport in dielectric polymers, which leads to the substantial performance improvements. The all-organic composites can be fabricated into large-area and high-quality films with uniform dielectric and capacitive performance, which is crucially important for their successful commercialization and practical application in high-temperature electronics and energy storage devices. Dielectric polymers are widely used in electrostatic energy storage but suffer from low energy density and efficiency at elevated temperatures. Here, the authors show that all-organic composites containing high-electron-affinity molecular semiconductors exhibit excellent capacitive performance at 200 °C.

191 citations


Journal ArticleDOI
TL;DR: In this article, the relationship among the structure, dielectric, and impedance properties of Sr2+ substituted barium titanate (BST) ceramics is investigated. But, the analysis is limited to the case where the as-prepared samples are characterized by X-ray diffraction and Raman spectroscopy.

181 citations


Journal ArticleDOI
TL;DR: The proposed crossover relaxor ferroelectrics (CRFE) exhibits smaller free energy and lower defect density in modified Landau theory, which benefits to obtain ultra-high energy density and efficiency and a promising candidate to meet the wide requirements for high power applications.
Abstract: Although extensive studies have been done on lead-free dielectric ceramics to achieve excellent dielectric behaviors and good energy storage performance, the major problem of low energy density has not been solved so far. Here, we report on designing the crossover relaxor ferroelectrics (CRFE), a crossover region between the normal ferroelectrics and relaxor ferroelectrics, as a solution to overcome the low energy density. CRFE exhibits smaller free energy and lower defect density in the modified Landau theory, which helps to obtain ultrahigh energy density and efficiency. The (1-x)Ba0.65Sr0.35TiO3-xBi(Mg2/3Nb1/3)O3 ((1-x)BST-xBMN) (x = 0, 0.08, 0.1, 0.18, 0.2) ceramic was synthesized by a solid-state reaction method. The solid solutions exhibit dielectric frequency dispersion, which suggests typical relaxor characteristics with the increasing BMN content. The crossover ferroelectrics of 0.9BST-0.1BMN ceramic possesses a high energy storage efficiency (η) of 85.71%, a high energy storage density (W) of 3.90 J/cm3, and an ultrahigh recoverable energy storage density (Wrec) of 3.34 J/cm3 under a dielectric breakdown strength of 400 kV/cm and is superior to other lead-free BaTiO3 (BT)-based energy storage ceramics. It also exhibits strong thermal stability in the temperature range from 25 to 150 °C under an electric field of 300 kV/cm, with the fluctuations below 3% and with the energy storage density and energy efficiency at about 2.8 J/cm3 and 82.93%, respectively. The enhanced recoverable energy density and breakdown strength of BT-based materials with significantly high energy efficiency make it a promising candidate to meet the wide requirements for high power applications.

167 citations


Journal ArticleDOI
TL;DR: In this paper, a core-shell BaTiO3@MgO (BT@MO) nanostructure was fabricated, in which highly insulating MgO was directly coated on a continuous ferroelectric nanoparticle BaO3 shell through a chemical precipitation method to improve the breakdown strength and electric displacement under high electric field.
Abstract: Dielectric energy storage capacitors are critical components widely used in electronic equipment and power systems due to their advantages of ultrahigh power density and high voltage. Herein, a novel core–shell BaTiO3@MgO (BT@MO) nanostructure was fabricated, in which highly insulating MgO was directly coated on a continuous ferroelectric nanoparticle BaTiO3 shell through a chemical precipitation method to improve the breakdown strength and electric displacement under high electric field. A large electric displacement (D ≈ 9.8 μC cm−2 under 571.4 MV m−1) was observed along with a high discharge energy density (Ud ≈ 19.0 J cm−3) for BT@MO/P(VDF-HFP) composites, which was 187% higher than that for a P(VDF-HFP) film when the filler content was 3 wt%. The enhancement rate of Ud in this study achieved the highest level among the reported results. It was revealed that the highly insulating MgO shell can enhance the breakdown strength by preventing charge injection from electrodes and impeding the development of electrical stress during the breakdown process, as confirmed by the leakage current measurements and the finite element simulations. The core–shell BT@MO structured filler provided an effective way to improve the energy storage properties of the polymer-based dielectrics.

Journal ArticleDOI
TL;DR: In this paper, the authors present a systematic strategy to optimise dielectric breakdown strength and maximum polarisation via Nb-doping to increase resistivity by eliminating hole conduction and promoting electrical homogeneity and alloying with a third perovskite end-member, BiMg2/3Nb1/3O3 (BMN), to reduce long range polar coupling without decreasing the average ionic polarisability.
Abstract: The Gerson–Marshall (1959) relationship predicts an increase in dielectric breakdown strength (BDS) and therefore, recoverable energy density (Wrec) with decreasing dielectric layer thickness. This relationship only operates however, if the total resistivity of the dielectric is sufficiently high and the electrical microstructure is homogeneous (no short circuit diffusion paths). BiFeO3–SrTiO3 (BF–ST) is a promising base for developing high energy density capacitors but Bi-rich compositions which have the highest polarisability per unit volume are ferroelectric rather than relaxor and are electrically too conductive. Here, we present a systematic strategy to optimise BDS and maximum polarisation via: (i) Nb-doping to increase resistivity by eliminating hole conduction and promoting electrical homogeneity and (ii) alloying with a third perovskite end-member, BiMg2/3Nb1/3O3 (BMN), to reduce long range polar coupling without decreasing the average ionic polarisability. These strategies result in an increase in BDS to give Wrec = 8.2 J cm−3 at 460 kV cm−1 for BF–ST–0.03Nb–0.1BMN ceramics, which when incorporated in a multilayer capacitor with dielectric layers of 8 μm thickness gives BDS > 1000 kV cm−1 and Wrec = 15.8 J cm−3.

Journal ArticleDOI
TL;DR: It is shown that nanofillers at very low volume content in a high-temperature (high–glass transition temperature) semicrystalline dipolar polymer, poly(arylene ether urea), can generate local structural changes, leading to a marked increase in both dielectric constant and breakdown field, and substantially reduce conduction losses at high electric fields and over a broad temperature range.
Abstract: Although many polymers exhibit excellent dielectric performance including high energy density with high efficiency at room temperature, their electric and dielectric performance deteriorates at high temperatures (~150°C). Here, we show that nanofillers at very low volume content in a high-temperature (high–glass transition temperature) semicrystalline dipolar polymer, poly(arylene ether urea), can generate local structural changes, leading to a marked increase in both dielectric constant and breakdown field, and substantially reduce conduction losses at high electric fields and over a broad temperature range. Consequently, the polymer with a low nanofiller loading (0.2 volume %) generates a high discharged energy density of ca. 5 J/cm3 with high efficiency at 150°C. The experimental data reveal microstructure changes in the nanocomposites, which, at 0.2 volume % nanofiller loading, reduce constraints on dipole motions locally in the glassy state of the polymer, reduce the mean free path for the mobile charges, and enhance the deep trap level.

Journal ArticleDOI
15 Oct 2020-Carbon
TL;DR: In this paper, the authors proposed a low-cost, simple preparation process and excellent absorbing performance promise BC/Fe3O4@C nanocomposites being an excellent lightweight electromagnetic wave absorber.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a P(VDF-HFP)-based nanocomposite by a simple and practical mechanical method based on a combination of solid phase reaction and sieving to prepare 0.88BaTiO3-0.12Bi(Li 0.5Nb0.5)O3 nanoparticles.

Journal ArticleDOI
TL;DR: In this article, a multi-phase coexistence material system is proposed to obtain stable dielectric and energy storage properties for high-temperature dielectrically stable capacitated capacitors.
Abstract: High-temperature dielectric ceramics are in urgent demand due to the rapid development of numerous emerging applications. However, producing dielectric ceramics with favorable temperature, frequency and electric field stability is still a huge challenge. The construction of multi-phase coexistence material systems is an effective way to obtain stable dielectric and energy storage properties. In this work, NaNbO3 (NN) modified 0.95Bi0.5Na0.5TiO3–0.05SrZrO3 (BNTSZ) ceramics ((1 − x)BNTSZ–xNN) are designed to achieve the coexistence of rhombohedral and tetragonal phases. The variation in the dielectric permittivity of the 0.8BNTSZ–0.2NN ceramic is less than ±15% over the temperature range from −55 °C to 545 °C, which is the reported record-high upper operating temperature, with a high room-temperature dielectric permittivity of 1170. The 0.8BNTSZ–0.2NN ceramic exhibits excellent frequency and electric field stability as well. Additionally, a large discharge energy density of 3.14 J cm−3 is obtained in the 0.85BNTSZ–0.15NN ceramic with an energy efficiency of 79% at a high temperature of 120 °C under 230 kV cm−1, with the variation in the discharge energy density being less than ±4% in the temperature range from 25 °C to 180 °C under 120 kV cm−1. All these features demonstrate that the (1 − x)BNTSZ–xNN ceramics are promising candidates for use at extremely high temperature in both dielectric and energy storage capacitor applications.

Journal ArticleDOI
03 Jul 2020-Science
TL;DR: It is shown that high-energy ion bombardment improves the energy storage performance of relaxor ferroelectric thin films and suggests that postprocessing may be important for developing the next generation of capacitors.
Abstract: Dielectric capacitors can store and release electric energy at ultrafast rates and are extensively studied for applications in electronics and electric power systems Among various candidates, thin films based on relaxor ferroelectrics, a special kind of ferroelectric with nanometer-sized domains, have attracted special attention because of their high energy densities and efficiencies We show that high-energy ion bombardment improves the energy storage performance of relaxor ferroelectric thin films Intrinsic point defects created by ion bombardment reduce leakage, delay low-field polarization saturation, enhance high-field polarizability, and improve breakdown strength We demonstrate energy storage densities as high as ~133 joules per cubic centimeter with efficiencies exceeding 75% Deterministic control of defects by means of postsynthesis processing methods such as ion bombardment can be used to overcome the trade-off between high polarizability and breakdown strength

Journal ArticleDOI
TL;DR: In this paper, a series of core-shell Co@C nanotubes were produced via facile pyrolysis of cobalt carbonate hydroxide hydrate/dopamine precursor.
Abstract: Rationally engineering on nanostructure of electromagnetic absorbers provides massive potential for eliminating the pollution caused by electromagnetic radiation. In this work, a series of core-shell Co@C nanotubes were produced via facile pyrolysis of cobalt carbonate hydroxide hydrate/dopamine precursor. Thanks to the well introduction of core-shell and nanotube structure, Co@C composite shows more superior microwave absorption than pristine Co nanoparticles. The unique microstructure provides abundant heterostructures and conductive paths to induce interfacial polarization and conductive loss for boosting dielectric loss. Through regulating the graphitization layer of C shell, the dielectric property could be further enhanced. Coupled with the favorable magnetic loss from the embedded Co nanoparticles, the products exhibit an optimal absorption intensity of −48 dB under low filler content of 30%. And effective absorption frequency bandwidth is up to 5.2 GHz at small thickness of 1.8 mm. Such excellent achievements demonstrate that the core-shell Co@C nanotube composites can be applied as a promising candidate for lightweight and thin electromagnetic absorption.

Journal ArticleDOI
25 Jun 2020-Nature
TL;DR: Th Thin films of amorphous boron nitride are mechanically and electrically robust, prevent diffusion of metal atoms into semiconductors and have ultralow dielectric constants that exceed current recommendations for high-performance electronics.
Abstract: Decrease in processing speed due to increased resistance and capacitance delay is a major obstacle for the down-scaling of electronics1-3 Minimizing the dimensions of interconnects (metal wires that connect different electronic components on a chip) is crucial for the miniaturization of devices Interconnects are isolated from each other by non-conducting (dielectric) layers So far, research has mostly focused on decreasing the resistance of scaled interconnects because integration of dielectrics using low-temperature deposition processes compatible with complementary metal-oxide-semiconductors is technically challenging Interconnect isolation materials must have low relative dielectric constants (κ values), serve as diffusion barriers against the migration of metal into semiconductors, and be thermally, chemically and mechanically stable Specifically, the International Roadmap for Devices and Systems recommends4 the development of dielectrics with κ values of less than 2 by 2028 Existing low-κ materials (such as silicon oxide derivatives, organic compounds and aerogels) have κ values greater than 2 and poor thermo-mechanical properties5 Here we report three-nanometre-thick amorphous boron nitride films with ultralow κ values of 178 and 116 (close to that of air, κ = 1) at operation frequencies of 100 kilohertz and 1 megahertz, respectively The films are mechanically and electrically robust, with a breakdown strength of 73 megavolts per centimetre, which exceeds requirements Cross-sectional imaging reveals that amorphous boron nitride prevents the diffusion of cobalt atoms into silicon under very harsh conditions, in contrast to reference barriers Our results demonstrate that amorphous boron nitride has excellent low-κ dielectric characteristics for high-performance electronics

Journal ArticleDOI
TL;DR: In this paper, a new class of all-polymer based high-temperature dielectric materials prepared from crosslinking of melt-processable fluoropolymers is reported.
Abstract: The electrification of transport requires dielectric materials capable of operating efficiently at high temperatures to meet the increasing demand of electrical energy storage at extreme conditions. Current high-temperature dielectric polymers rely on the incorporation of wide bandgap inorganic fillers to restrain electrical conduction and achieve high efficiencies at elevated temperatures. Here, we report a new class of all-polymer based high-temperature dielectric materials prepared from crosslinking of melt-processable fluoropolymers. The crosslinked polymers exhibit larger discharged energy densities and greater charge–discharge efficiencies along with excellent breakdown strength and cyclic stability at elevated temperatures when compared to the current dielectric polymers. The origins of the marked improvement in the high-temperature capacitive performance are traced to efficient charge-trapping by a range of the molecular trapping centers resulting from the crosslinked structures. In addition, the implementation of melt-extrudable polymers would enable scalable processing that is compatible with the current fabrication techniques used for polymer dielectrics, which is in sharp contrast to the dielectric polymer composites with inorganic fillers.

Journal ArticleDOI
TL;DR: In this article, two kinds of low-sintering temperature and high-performance microwave dielectric ceramics with monoclinic rock salt structure by adding a small amount of V2O5 and 0.4B2O3 sintering aids to Li2Ti0.75(Mg1/3Nb2/3)0.25O3 (LTMN 0.25).
Abstract: Microwave dielectric ceramics are considered to be one of the key materials of dielectric resonators/filters and have wide application prospects in fifth generation (5G) mobile communication systems. Here we prepared two kinds of low-sintering temperature and high-performance microwave dielectric ceramics with monoclinic rock salt structure by adding a small amount of V2O5 and 0.6CuO–0.4B2O3 sintering aids to Li2Ti0.75(Mg1/3Nb2/3)0.25O3 (LTMN0.25). The sintering temperature of LTMN0.25 ceramics with 2 wt% V2O5 and 1 wt% 0.6CuO–0.4B2O3 additions could be effectively reduced from 1170 °C to below 910 °C due to the liquid phase effects resulting from the additives. Typically, high performance microwave dielectric properties can be obtained in the LTMN0.25 + 2 wt% V2O5 ceramic sintered at 910 °C for 2 h, with a er ∼ 20.7, a Q × f ∼ 60 460 GHz and a TCF ∼ +4.3 ppm °C−1. The best dielectric properties of er ∼ 19.9, a Q × f ∼ 60 950 GHz and a TCF ∼ −6.1 ppm °C−1 were obtained for the samples with 1 wt% 0.6CuO–0.4B2O3 sintered at 870 °C for 2 h. A prototype dielectric resonator antenna (DRA) was fabricated by LTMN0.25 + 1 wt% 0.6CuO–0.4B2O3 ceramic. The antenna resonated at 10.02 GHz with a bandwidth ∼175 MHz at −10 dB transmission loss (S11). Moreover, the chemical compatibility with Ag powder suggests that the LTMN0.25 + 2 wt% V2O5 and LTMN0.25 + 1 wt% 0.6CuO–0.4B2O3 ceramics may be suitable candidates for low temperature co-fired ceramic technology applications.

Journal ArticleDOI
TL;DR: In this article, two kinds of lead-free relaxor-ferroelectric BNT-based ceramic hierarchical polycrystalline alloys (La3Ni2O7/LaNiO3, La2NiO4/La2O3) were prepared via a facile solvothermal and high-temperature annealing technique as high-performance EMW absorption materials (MAMs).

Journal ArticleDOI
TL;DR: This review focuses on recent advances in polymer-matrix nanocomposites using various types of 1D nanofillers, i.e., linear, ferroelectric, paraelectric, and relaxor-ferroelectric for energy storage applications.
Abstract: Recent developments in various technologies, such as hybrid electric vehicles and pulsed power systems, have challenged researchers to discover affordable, compact, and super-functioning electric energy storage devices. Among the existing energy storage devices, polymer nanocomposite film capacitors are a preferred choice due to their high power density, fast charge and discharge speed, high operation voltage, and long service lifetime. In the past several years, they have been extensively researched worldwide, with 0D, 1D, and 2D nanofillers being incorporated into various polymer matrixes. However, 1D nanofillers appeared to be the most effective in producing large dipole moments, which leads to a considerably enhanced dielectric permittivity and energy density of the nanocomposite. As such, this Review focuses on recent advances in polymer matrix nanocomposites using various types of 1D nanofillers, i.e., linear, ferroelectric, paraelectric, and relaxor-ferroelectric for energy storage applications. Correspondingly, the latest developments in the nanocomposite dielectrics with highly oriented, surface-coated, and surface-decorated 1D nanofillers are presented. Special attention has been paid to identifying the underlying mechanisms of maximizing dielectric displacement, increasing dielectric breakdown strength, and enhancing the energy density. This Review also presents some suggestions for future research in low-loss, high energy storage devices.

Journal ArticleDOI
TL;DR: In this paper, the authors comprehensively summarize the research progress of lead-free dielectric ceramics for energy storage, including ferroelectric, composite, and multilayer capacitors.
Abstract: Energy storage materials and their applications have attracted attention among both academic and industrial communities. Over the past few decades, extensive efforts have been put on the development of lead-free high-performance dielectric capacitors. In this review, we comprehensively summarize the research progress of lead-free dielectric ceramics for energy storage, including ferroelectric ceramics, composite ceramics, and multilayer capacitors. The results indicate that dielectric capacitors with both high energy density and high efficiency are feasible using the materials providing high breakdown electric field and a slim hysteresis loop. This article also lists the factors affecting the fabrication cost of dielectric capacitors, such as sintering temperature, raw material costs, and types of internal electrodes, to promote the industrial application of ceramic energy storage capacitors.

Journal ArticleDOI
TL;DR: In this paper, a new energy storage dielectric system-polyetherimide (PEI) based composite was developed and investigated intensively, which possesses the advantages of excellent energy storage efficiency along with energy storage density.

Journal ArticleDOI
TL;DR: In this article, hexagonal boron nitride (h-BN) layers with different thickness playing roles in thermal conduction and carrier blocking are designed and transferred on both sides of polycarbonate (PC) films.

Journal ArticleDOI
TL;DR: In this paper, two methods are explored to ameliorate the ultra-high complex permittivity of carbon materials, and the obtained honeycomb-like porous SCFs@Fe3O4@FeO (S4) composite has superior EMW absorption performance.
Abstract: In recent years, the development of an electromagnetic wave (EMW) absorbing material with low cost, wide bandwidth and strong absorption strength has been widely explored. In this study, SCFs@Fe3O4 was used as the precursor (S1), and two methods are explored to ameliorate the ultra-high complex permittivity. The method of adding phenolic resin has achieved ideal results, and its bamboo-like SCFs@Fe3O4@phenolic resin (PR) (S5) has excellent property. In addition, the electromagnetic properties can be improved by calcining the precursor at 700 °C in a tubular furnace protected by Ar gas, and the obtained honeycomb-like porous SCFs@Fe3O4@FeO (S4) composite has superior EMW absorption performance. The excellent EMW absorption performance comes from its unique porous structure. The sample also has a dual loss mechanism of dielectric and magnetic loss. Among them, conduction loss, interfacial polarization, Debye relaxation, hysteresis loss, natural ferromagnetic resonance and exchange resonance play an important role in the process of EMW absorption. It exhibits an effective absorption bandwidth (EAB) of 6.1 GHz with a thin thickness of 1.9 mm. Noting that, by adjusting the thickness (1–5 mm), reflection loss (RL) lower than −10 dB can be achieved in the range of 4–18 GHz, which covers the entire C, X and Ku bands. In this study, we not only successfully prepared honeycomb-like porous SCFs@Fe3O4@FeO and bamboo-like SCFs@Fe3O4@PR, but also proposed two simple methods to solve the excessively high complex permittivity of carbon materials. This has important reference value for the subsequent research of EMW absorbing materials.

Journal ArticleDOI
TL;DR: In this article, a (1-x)NBT-xBH transparent ceramic was fabricated by the solid state reaction method and X-ray diffraction analysis showed that NBT-based transparent ceramics exhibit a cubic-like perovskite structure and the solid solubility of BH in NBT reached to 0.15.
Abstract: A novel (1-x)Na0.5Bi0.5TiO3-xBaHfO3 (abbreviated as (1-x)NBT-xBH) transparent ceramic was fabricated by the solid state reaction method. X-ray diffraction analysis showed that NBT-based transparent ceramics exhibit a cubic-like perovskite structure and the solid solubility of BH in NBT reached to 0.15. The Landau-Devonshire theory and I-E curves revealed that the transition between the antiferroelectric like phase and the ferroelectric phase deeply relies on the variation of composition and free energy. One sample (x = 0.15) was found to show a high dielectric constant (˜2418±10%) over the temperature range 57–400 °C. These ceramics also exhibited a high discharge energy density (Wd) of 2.1 J/cm3 and a high maximum polarization Pm of 34 μC/cm2 under relatively low electric fields which were less than 175 kV/cm. There was also high transparency in the visible spectra (more than 0.5) when the sample thickness was 250 μm.

Journal ArticleDOI
TL;DR: The usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof of concept material and new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries are proposed.
Abstract: High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.

Journal ArticleDOI
TL;DR: In this article, a cost-effective preparation of 2D MXene (Ti3C2Tx) filled polyvinylidene fluoride (PVDF) polymer nanocomposite for the attenuation of electromagnetic interference (EMI) is presented.
Abstract: The present study deals with novel, and cost-effective preparation of 2D MXene (Ti3C2Tx) filled polyvinylidene fluoride (PVDF) polymer nanocomposite for the attenuation of electromagnetic interference (EMI). The obtained nanocomposite showed remarkable shielding effectiveness (SE) of 48.47 ± 3.5 dB for 22.55 vol% filler contents at a thickness of 2 mm. Formation of conducting network along with the assembly of micro capacitor network preserved for its high EMI shielding performance. The absorption dominated EMI shielding mechanism explained by the strong resonance, and interfacial polarization favors the loss of incident EM energy confirmed from dielectric measurements. Besides, the enhanced thermal conductivity of MXene-PVDF nanocomposites about 0.767 ± 0.034 Wm−1K−1 at 22.55 vol% filler content depicts that a large amount of incident EM wave attenuated majorly by dielectric components which would be dissipated as heat quickly. The fabricated MXene-PVDF nanocomposites could be a potential candidate for EMI shielding materials and promising multifaceted electronic utilization.