High Dielectric Breakdown Strength Research Articles

Combined Merits of High Dielectric Breakdown Strength and Low Sintering Temperature Acquired in Mgo-Baseddielectric Ceramics: From Theoretical Prediction to Experimental Validation

Dilemma of dielectric breakdown has perplexed researchers for decades while intrinsic factors accounting for dielectric breakdown strength (DBS) is still unsettled. In this work to address the great deterioration of DBS after LiF acceptor doping in MgO (LMO), high throughout first principles calculation is carried out to screen nearly 30 cations from donor doping perspective. The work function from the theoretical calculation, as a descriptor correlated to electronic property, displays a linear correlation with experimental DBS while Mn is proven to be the best candidate dopant for its greatly improvement on work function of LMO system and therefore a markedly enhanced DBS. Detailed analysis manifests that MnCO3 incorporation further decreases the sintering temperature of LMO to 900 °C and also leads to defect associations between oxygen vacancies and cation substitutional defects, causing distinct change in dielectric behavior and conduction mechanism. Afterwards, beneficial effects of grain refinement and increased grain boundary resistivity on DBS are analyzed using phase field modeling method. With all these merits, nearly 85% improvement in DBS is achieved in 1 wt% MnCO3 tailored LMO. This work not only reveals the decisive role of work function in DBS prediction therefore shed light on composition design of dielectrics, but also provides a paradigm combining ions screening, theoretical prediction, experiments and simulation together to greatly accelerate the materials research.

Nanocluster-Based Ultralow-Temperature Driven Oxide Gate Dielectrics for High-Performance Organic Electronic Devices.

The development of novel dielectric materials with reliable dielectric properties and low-temperature processibility is crucial to manufacturing flexible and high-performance organic thin-film transistors (OTFTs) for next-generation roll-to-roll organic electronics. Here, we investigate the solution-based fabrication of high-k aluminum oxide (Al2O3) thin films for high-performance OTFTs. Nanocluster-based Al2O3 films fabricated by highly energetic photochemical activation, which allows low-temperature processing, are compared to the conventional nitrate-based Al2O3 films. A wide array of spectroscopic and surface analyses show that ultralow-temperature photochemical activation (<60 °C) induces the decomposition of chemical impurities and causes the densification of the metal-oxide film, resulting in a highly dense high-k Al2O3 dielectric layer from Al-13 nanocluster-based solutions. The fabricated nanocluster-based Al2O3 films exhibit a low leakage current density (<10−7 A/cm2) at 2 MV/cm and high dielectric breakdown strength (>6 MV/cm). Using this dielectric layer, precisely aligned microrod-shaped 2,7-dioctyl[1]benzothieno [3,2-b][1] benzothiophene (C8-BTBT) single-crystal OTFTs were fabricated via solvent vapor annealing and photochemical patterning of the sacrificial layer.

Enabling High Dielectric Response in PVDF/V2C MXene–TiO2 Composites Based on Nontypical V–F–Ti Bonding and Fermi-Level Overlapping Mechanisms

High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO2 with low dielectric constant and V2C MXene with high work function are n...

Relaxor regulation and improvement of energy storage properties of Sr2NaNb5O15-based tungsten bronze ceramics through B-site substitution

• A novel type of lead- and bismuth-free TTB relaxor is obtained. • The relationship between structure and electrical behavior is studied in detail. • Enhanced relaxation and high BDS are obtained based on B-site substitution. • The current ceramics show the high W re of 2.03 J/cm 3 and the η of 94%. • Excellent charging-discharging performance of W dis of 2.22 J/cm 3 and 151.1 MW/cm 3 of P D are achieved. Based on B-site substitution, a series of Sr 1.88 La 0.12 NaNb 4.88−x Ta x Ti 0.12 O 15 tungsten bronze ceramics were prepared by traditional solid-reaction. The influence of Ta replacement on dielectric relaxor, electrical and energy storage properties has been studied in detail. The change of dielectric properties deviates from the previous crystal chemical framework, and is closely related to the structural distortion caused by the special electronic configuration of Ta. In addition, an enhanced dielectric breakdown strength was obtained, which benefited from the dense microstructure, improved insulation and widened band gap. Finally, under the combined influence of good relaxation and high dielectric breakdown strength, an energy storage density of 2.03 J/cm 3 and an efficiency of 94% were achieved. More importantly, the charging-discharging performance has also been evaluated. The discharge energy density of 2.22 J/cm 3 and the power density of 151.1 MW/cm 3 indicate that the present ceramics are promising as high-power energy storage capacitor applications.

Crystal Growth of Epitaxial 3C-SiC Thin Film on Si Substrate by Chemical Vapor Deposition using Single Precursor of Vinylsilane

Cubic silicon carbide (3C-SiC) has attracted much attention since it has a wide bandgap, high dielectric breakdown strength, and high thermal stability. 3C-SiC promises various electronic applications such as power devices and MEMS. Also, 3C-SiC has an advantage for a lower cost among many SiC polytypes, as it can grow epitaxially on Si substrate. Generally, two types of precursor source materials, including Si and C, are necessary to grow 3C-SiC thin films for chemical vapor deposition (CVD) method. In addition, complex processes including carbonization with a temperature as high as about 1200 °C are required for conventional epitaxial growth of 3C-SiC [1]. We focus on vinylsilane as a single precursor material for SiC growth. The Si-C bond in vinylsilane is relatively stable due to the relationship of intramolecular bond energy, that is appreciable for SiC growth. The growth of SiC crystals using vinylsilane can be achieved at a low temperature of 1000 ºC or less and the deposition process will be simplified. Recently, we have achieved the formation of polycrystalline SiC thin films on metal substrate using CVD method only with vinylsilane [2]. In this study, we examine the epitaxial growth of 3C-SiC and also report phosphorous (P) doping for SiC thin films grown on Si substrate.SiC thin films were deposited on Si(001) and Si(111) substrates using CVD method with a vinylsilane precursor (manufactured by Japan Advanced Chemicals Co., Ltd.). The substrate temperature of the growth was ranging from 900 to 1000 °C, the growth pressure was 17 kPa, and the growth time was 60 min.The surface morphology of deposited film was observed using scanning electron microscopy (SEM). We can confirm that the uniform morphology of SiC film was formed on the Si substrate for a sample prepared with Si(111) substrate at 1000 ºC and also that there are no voids or defects at the interface.We also examined X-ray diffraction measurements to characterize the crystalline structure. Out-of-plane XRD measurement (2θ/ω method) shows a sufficiently large diffraction peak related to 3C-SiC(111) for the Si(111) sample prepared at 1000 ºC, which means the growth of a well (111)-oriented 3C-SiC thin film on Si(111) substrate. On the other hand, in the case of the grazing angle XRD measurement (2θ method) for the SiC/Si(001) samples prepared at both 900 and 1000 ºC, we observed many diffraction peaks meaning the formation of polycrystalline 3C-SiC. The analysis of peak intensity and full width at half maximum value (FWHM) revealed that the crystallinity of SiC film improved with increasing the growth temperature. Raman scattering spectroscopy measurement also revealed that the dominant bonding structure in the film is Si-C and not C-Hn or C-C for samples prepared at higher than 900 ºC, that means the formation of a high crystalline quality SiC thin film.In our presentation, we will discuss pros and cons of epitaxial growth of SiC films on Si(111) substrates and also reports P-doping into the SiC films will be discussed.

Increased Energy-Storage Density and Superior Electric Field and Thermally Stable Energy Efficiency of Aerosol-Deposited Relaxor (Pb0.89La0.11)(Zr0.70Ti0.30)O3 Films

(Pb0.89La0.11)(Zr0.70Ti0.30)O3 (PLZT 11/70/30) relaxor ferroelectric (RFE) films were fabricated on Pt/Si substrates by aerosol deposition, which not only enabled the deposition of a film at room temperature but also increased the dielectric breakdown strength. Perovskite phase and microstructural analyses were carried out by x-ray diffraction and scanning electron microscopy techniques. A PLZT 11/70/30 RFE AD film annealed at 550 °C exhibited the best dielectric properties (er ~ 1090, tanδ ~ 0.028) and typical relaxor-type slim polarization–electric field (P–E) hysteresis loop with relatively low remanent polarization (Pr ~ 6.81 µC/cm2) and coercive field (Ec ~ 118 kV/cm) even at a high applied electric field (~ 2500 kV/cm). These superior properties were achieved due to high phase purity, low defect densities, and well-tuned grain sizes of an annealed PLZT 11/70/30 RFE AD film. The PLZT 11/70/30 RFE AD film exhibited a high energy-storage density (Wrec ~ 44 J/cm3) which is attributed to the high dielectric breakdown strength, low hysteresis loss (Wloss ~ 10.3 J/cm3), and almost-electric-field-independent efficiency (η ~ 81%, change of ~ 6% with the change from low to high electric fields), calculated using the unipolar P–E hysteresis loop. The excellent temperature stability of the energy efficiency of the PLZT 11/70/30 RFE AD film makes it a promising material for high-temperature energy-storage capacitor applications.

High energy density and high efficiency achieved in the Ca0.74Sr0.26Zr0.7Ti0.3O3 linear dielectric thin films on the silicon substrates

Linear dielectrics are promising candidates for high-performance energy storage applications with high efficiency, excellent thermal stability, and high reliability due to their low loss, high dielectric breakdown strength, and stable dielectric properties, which are independent of the electric field and temperature. However, their low dielectric constant or polarization restricts the stored electrical energy, which makes them less attractive for high energy density storage applications compared to relaxor ferroelectrics or anti-ferroelectrics. Here, we realized an ultrahigh energy density (Ue ∼ 59.4 J/cm3) and high efficiency (∼89%) simultaneously in the Ca0.74Sr0.26Zr0.7Ti0.3O3 (CSZT) linear dielectric thin film, which are competitive with those of other lead-based and lead-free dielectric films deposited on Si wafers. Moreover, the CSZT thin-film capacitor exhibits great thermal stability with the Ue variation less than 3% from −90 °C to 170 °C and good fatigue endurance with the Ue variation of 4.5% after 3 × 107 cycles at 10 kHz. This work also reveals that the exploration of advanced linear dielectric thin films with a medium dielectric constant would benefit from the development of high-performance energy-storage capacitors.

Origin of superb electrical insulating capability of cellulose-liquid biphasic dielectrics by interfacial charge behaviors

The cellulose-liquid biphasic dielectric composite serves as the irreplaceable main electrical insulating structure in the power industry, owing to its peculiar high dielectric breakdown strength compared to that of monophasic cellulose paper or insulating liquid. Although this advanced electrical characteristic is utilized worldwide, its physical–chemical nature remains unclear, which greatly restricts the design and improvement of next generation electrical insulating composites. Herein, the interfacial charge behaviors in cellulose-liquid composites are investigated, and the results indicate that the majority of charge carriers in insulating liquid are electrostatically adsorbed at the nano-scale interface, forming interfacial charge traps, leading to 17.66 times increased deep trap density, which suppress further charge migration under high voltages, and consequently lead to the ∼400% improved dielectric breakdown strength compared to that of cellulose paper and insulating liquid. By controlling the interfacial trap characteristics with insulating liquids of strong electron withdrawing ability, the resistivity and breakdown strength of cellulose-liquid composites are further improved.

Low-temperature-poling awakened high dielectric breakdown strength and outstanding improvement of discharge energy density of (Pb,La)(Zr,Sn,Ti)O3 relaxor thin film

Abstract Ferroelectric thin films possessing high dielectric breakdown strength (DBS) are attractive materials employed to satisfy the requirements of miniaturization and integration of electronic components, especially for dielectric capacitors with large discharge energy density (W). In this work, it is demonstrated for the first time that high DBS in ferroelectric thin film can be awakened by a low-temperature-poling method. Mn-doped Pb0.97La0.02(Zr0.905Sn0.015Ti0.08)O3 (PLZST) relaxor thin films were prepared by using a sol-gel method, as when poled at near liquid nitrogen temperature, its DBS and W at room temperature are greatly enhanced (nearly doubled) from 1286 kV/cm to 2000 kV/cm, and from 16.6 J/cm3 to 31.2 J/cm3, respectively. The high ordering of defect dipoles during the low-temperature-poling process is responsible for the great enhancement of the awakened DBS and the outstanding improvement of the W. It concludes that the low-temperature-poling method can provide a new alternative strategy to strength the DBS and thus to improve the electrical performances of ferroelectric materials for the applications required strong electric fields in many fields, especially for dielectric energy storage, electrocaloric cooling, and energy harvesting, etc.

High breakdown strength and energy storage density of Er0.02Sr0.97TiO3@MgO2–Al2O3–SiO2 ceramics with core–shell structure sintered in oxygen atmosphere

Effects of different sintering atmospheres (O2 and air) on the energy storage properties and dielectric characteristics were systematically investigated for 2MgO–2Al2O3–5SiO2 (MAS)-coated Er0.02Sr0.97TiO3 (EST) ceramics. The core–shell structure was formed by the sol-precipitation method. The ceramic sintered in O2 features fine grain, excellent frequency stability, low leakage current, high dielectric breakdown strength (BDS), and high energy storage density (Wreco). Compared with air-sintered ceramics, the dielectric DC breakdown strength of ceramic sintered in oxygen atmosphere has been enhanced significantly from 375 to 590 kV/cm. Besides, the maximum Wreco of 2.01 J/cm3 and efficiency of 86.2% were obtained at 460 kV/cm, which demonstrated that the core–shell structure and atmosphere sintering provide an instructive strategy for the design of high energy storage materials.

Investigation on the dielectric performance of PVDF-HFP/LZO composites

Abstract The energy storage density of the film capacitor is crucial for optoelectronic devices. Among various dielectrics, polyvinylidene-fluoride-co-hexafluoropropylene (PVDF-HFP) copolymer is widely preferred due to its inherent high dielectric constant and breakdown strength. However, the low energy storage density and high dielectric loss (tan δ) of PVDF-HFP remains challenging in the present scenario. In this work, we demonstrated how to improve the dielectric constant and energy density of PVDF-HFP with low dielectric losses by formulating PVDF-HFP/Lanthanum Zirconium Oxide (LZO) composite ink at low temperature. We performed the computational modeling of the thin-film capacitor, consisting of PVDF-HFP/LZO as a dielectric layer, to find the optimum LZO content for achieving a high energy density. A computational model of the film capacitor and dielectric shielding was built with PVDF-HFP/LZO composites having a different LZO content to understand its effect on the electric field distribution, polarization, and energy storage density. We compared the dielectric properties of the PVDF-HFP/LZO thin-film capacitor predicted by simulations with the experimental values measured by impedance analysis. The optimum LZO content in PVDF-HFP was determined as 15 vol% to achieve a high energy storage density of 15.8 J/cm3 at 545 MV/m breakdown strength with low dielectric losses. Dielectric constant and energy storage density of the PVDF-HFP/LZO15 composite film were nearly doubled compared to that of neat PVDF-HFP by keeping dielectric losses low.

High dielectric and breakdown performances achieved in PVDF/graphene@MXene nanocomposites based on quantum confinement strategy

Graphene nanosheets are widely employed for fabricating high-dielectric-constant polymer nanocomposites for energy storage. However, severely reduced electric breakdown strengths of composites with increasing graphene content limit their high-field applications. To improve breakdown strengths of polyvinylidene fluoride/graphene composites without sacrificing dielectric constants, in this work, we proposed a rational strategy of constructing MXene quantum dot inter-layers for preparing ternary composites with desirable electric properties, owing to inter-layer induced quantum confinement and Coulomb blockade effects. Graphene oxide@nitrogen-doped Ti3C2 MXene quantum-dot hybrid nanoparticles were synthesized via hydrogen-bond induced self-assembly route. Binary polymer/graphene and ternary polymer/hybrid-particle nanocomposite films were fabricated by solution cast process. Compared with binary composites, ternary counterparts have synergistically improved dielectric constants and breakdown strengths. Repeated disorder-bounce of electrons and strong coupling between electrons and holes, inside each quantum dot, might be responsible for superior electric performances of ternary composites. High dielectric constant (~53@1 kHz) and breakdown strength (~205 MV m−1) were realized in ternary composite with 0.12 wt % of nanoparticles. This work might pave a road for large-scale fabrication of high-performance nanocomposite dielectrics for energy storage.

Giant energy storage density in PVDF with internal stress engineered polar nanostructures

Abstract High power dielectric capacitors with high energy density are needed in order to develop modern electronic and electrical systems, including hybrid vehicles, telecommunication infrastructures and portable electronic devices. Relaxor ferroelectric polymers (RFP) are considered to be the most promising candidates for the next generation of capacitors owing to their relatively high energy storage density. However, the commercialization of RFP capacitors in power systems is hindered by their high cost and low dielectric breakdown strength. In this study, inexpensive, free-standing nano-crystalline (~3.3 nm) poly (vinylidene fluoride) (PVDF) films with high β phase content (~98%), “relaxor-like” ferroelectric behaviour and high breakdown strength (880 kV/mm) were fabricated using the facile Press & Folding (P&F) technique. An internal stress dominated polarization switching model is proposed to explain the origin of the relaxor-like ferroelectric behaviour. The internal stress generated during pressing alters the intermolecular chain distance of the (200) plane of β-PVDF from 4.24 A in internal stress free films to 4.54 A in P&F films, corresponding to a tensile strain and residual stress of 7.11% and 142 MPa, respectively. The internal stress acts to partially reverse the polarization on reversal of the applied electric field. This, combined with preferred in-plane orientation of the crystallites, results in a polar nanostructure with high polarization reversibility at high electric fields. A giant discharged energy storage density of 39.8 J/cm3 at 880 kV/mm was achieved for P&F films, which surpasses all previously reported polymer-based materials.

Improve the dielectric property and breakdown strength of composites by cladding a polymer/BaTiO3 composite layer around carbon nanotubes

This work offers a strategy for combining ceramic and conductive fillers to produce composites with high dielectric properties and breakdown strength through a novel core@shell structure. First, we successfully attached barium titanate (BT) nanoparticles to the surface of multi-walled carbon nanotubes (MWCNTs) by sol-gel method. Hyperbranched aromatic polyamide (HB-Pa) was grafted from the surface of BT-attached MWCNTs via in suit polymerization to obtain HB-Pa/BT composite-coated MWCNTs (H-B@CNTs). After the hybrid powders were compounded with epoxy resin (EP), composites with high dielectric properties were prepared. The H-B@CNTs/EP composite exhibited a dielectric constant of 110, a dielectric loss of 0.28 (1 kHz) and a breakdown strength of 6.7 kV/mm at 20 wt % MWCNTs content. The results indicated that we could tailor the dielectric properties of composites by adjusting the amount of BT nanoparticles on the surface of MWCNTs. In addition, HB-Pa played multiple roles in this system: (i) preventing BT nanoparticles from falling off the surface of MWCNTs; (ii) increasing the dispersibility and interaction of fillers in the polymer matrix; (iii) preventing MWCNTs from overlapping one another to form a conductive network to effectively improve the breakdown strength of composites.

Rejuvenation of Retired Power Cables by Heat Treatment: Experimental Simulation in Lab

In this work, heat treatment was performed on three retired 110 kV AC cables with service years of 0, 15 and 30, and the effects on the thermal and electrical performance of the cable insulation were investigated. First, each cable with a length approximately of 5 m was prepared and cut into five equal segments. Four segments of each cable were annealed at a temperature of 90, 95, 100, or 105 °C by building a small circuit to simulate cable operation. Then, a section at the middle of each segment was cut out, and the insulation layer was peeled away. The peeled-off layers from the inner, middle and outer positions were selected as the test samples. Subsequently, Fourier transform infrared spectrometry (FTIR), and differential scanning calorimetry (DSC) were performed, and the DC conduction current and dielectric breakdown strength were measured. The best thermal properties of the highest melting point, crystallinity, and smallest melting range were found when the cables were annealed at 100, 105, and 105 °C for the inner, middle, and outer positions, respectively. The highest dielectric breakdown strength and lowest electrical conductivity were found at temperatures of 95 or 100 °C for the inner and middle positions, respectively, and at 105 °C for the outer position. The FTIR results showed that thermal annealing for hundreds of hours did not adversely affect the molecular chains. It is found that this type of heat treatment could be a feasible method to rejuvenate retired cables, and a conservative temperature of 95 °C is regarded as the optimum annealing temperature.

Silica-decorated reduced graphene oxide (SiO2@rGO) as hybrid fillers for enhanced dielectric and actuation behavior of polydimethylsiloxane composites

A novel high performance dielectric elastomer actuator with a high dielectric constant, low dielectric loss, high dielectric breakdown strength and large actuated strain was prepared through introducing hybrid fillers of chemically reduced graphene oxide (rGO) covered by a SiO2 shell (SiO2@rGO). Hybrid particles were synthesized with two different shell coverage using tetraethylorthosilicate (TEOS) and characterized with different methods to identify the surface chemistry, inter-layer spacing, and thickness of the platelets as SiO2 shells were introduced and reduction process was applied. Composites of polydimethylsiloxane (PDMS) containing different amounts of rGO and SiO2@rGO particles were prepared by the solution mixing method. The results showed that composites with hybrid fillers have higher dielectric efficiency and dielectric strength than rGO/PDMS composites. However, higher actuated strains than the pure PDMS was obtained only with hybrid particles with dense coverage. Maximum actuated strain increased from 4.63% for the pure PDMS to 12.83% and 9.12% for composites with 1 wt% and 2 wt% of SiO2@rGO with denser SiO2 shell, respectively. Results suggest the positive effect of hybrid graphenic structures with high shell coverage and certain weight fraction toward preparing high performance dielectric elastomer actuator composites.

Enhanced energy density in Mn-doped (1-x)AgNbO3-xCaTiO3 lead-free antiferroelectric ceramics

Ceramics of 0.2 wt% Mn-doped (1-x)AgNbO3-xCaTiO3 (x = 0.00–0.04) were prepared in flowing oxygen with the solid state method. The microstructure, antiferroelectricity and energy storage performance were investigated to explore the potential for use in energy storage capacitors. Incorporation of CaTiO3 in AgNbO3 effectively inhibits the grain growth and gives rise to high dielectric breakdown strength. The temperature-dependent dielectric property and Raman spectroscopy measurements demonstrate the enhanced stability of antiferroelectricity by CaTiO3 addition through adjusting the M1–M2 phase transition. As a result of both improved antiferroelectricity and dielectric breakdown strength, a high recoverable energy density of 3.7 J/cm3 was achieved in the 2 mol% CaTiO3-modified AgNbO3 ceramic, which represents one of the highest recoverable energy density in recently studied lead-free ceramics. Furthermore, the energy storage performance displays an excellent thermal stability with a low variation (3%) over a wide temperature range (20–120 °C). These results indicate that modifying AgNbO3 simultaneously on the A- and B-sites in the ABO3 perovskite structure may lead to the discovery of new antiferroelectric materials with a high energy density.

Energy Storage Properties of Blended Polymer Films with Normal Ferroelectric P(VDF-HFP) and Relaxor Ferroelectric P(VDF-TrFE-CFE)

With the recent development of wearable/portable electronic devices, the power sources need to be flexible and miniaturized. As the power supply, a dielectric capacitor is used for systems requiring high power in a short time, which in turn necessitates dielectric materials with high energy density and fast discharging time for device miniaturization. In this study, we attempt to improve the energy density of organic materials by blending normal ferroelectric P(VDF-HFP), which offers high dielectric breakdown strength, and relaxor ferroelectric P(VDF-TrFE-CFE), which provides a high dielectric constant. The role of P(VDF-HFP) as a defect in the P(VDF-TrFE-CFE) crystallite improved the properties of the relaxor-ferroelectrics. Increasing the terpolymer content in the blended films reduced the normal ferroelectric β-phase, which revealed that non-polar phase was induced. The copolymer and terpolymer were blended in various weight ratios (10:0, 7:3, 5:5, 3:7, 1:9 and 0:10) and cast into films. The blends with a copolymer/terpolymer ratio of 1:9 showed reduced hysteresis and remnant polarization, compared to those of the pure terpolymer, and a higher maximum polarization (Pmax) value at an electric field of 250 MV/m, indicating a less saturated polarization at high electric field. To conclude, the PVDF-based copolymer/terpolymer (1:9 ratio) blends showed the highest energy density (6.58 J/cm3).

Crystal structure, relaxor behaviors and energy storage performance of (Sr0.7Ba0.3)5LaNb7Ti3O30 tungsten bronze ceramics

In this work, a new (Sr0.7Ba0.3)5LaNb7Ti3O30 system ceramic with a filled tetragonal tungsten bronze structure was proposed and fabricated by the traditional solid phase method. Crystal structure, relaxor behaviors and energy storage capabilities were studied. Large relaxor activation energy indicates a “weakly coupled relaxor” mechanism, which is advantageous for obtaining better energy storage performance, and lower conductance activation energy can further prove the formation of the filled tungsten bronze structure. More importantly, a dielectric breakdown strength of up to 35.5 kV/mm was obtained. The releasable energy density and efficiency at 24 kV/mm are 1.36J/cm3 and 91.9%, respectively. In addition, due to the high current density and high dielectric breakdown strength, a current density of 477.5 A/cm2 and a power density of 42.9 MW/cm3 are achieved, meaning that SBLNT ceramic is a potential candidate dielectric ceramic for energy storage.

Ultrahigh \u03b2-phase content poly(vinylidene fluoride) with relaxor-like ferroelectricity for high energy density capacitors

Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations. Herein, a facile process of pressing-and-folding is proposed to produce β-poly(vinylidene fluoride) (β-phase content: ~98%) with relaxor-like behavior observed in poly(vinylidene fluoride) with high molecular weight > 534 kg mol−1, without the need of any hazardous gases, solvents, electrical or chemical treatments. An ultra-high energy density (35 J cm−3) with a high efficiency (74%) is achieved in a pressed-and-folded poly(vinylidene fluoride) (670-700 kg mol−1), which is higher than that of other reported polymer-based dielectric capacitors to the best of our knowledge.