High Electrical Breakdown Strength Research Articles

Silicone elastomer with simultaneous enhanced healing and electrical resistance via fluorine substitution for actuator dielectrics

A fluorine substituted healable silicone elastomer is developed as actuator dielectric material in this study. The silicone possesses both high electrical breakdown strength (>65 kV/mm) and admirable intrinsic permittivity (more than 4.3 at 50 Hz). Moreover, with fluorine stimulated carbamate bond exchange, the networks of prepared silicones can be recovered with more than 80% of mechanical and insulating reprocessing efficiency. Importantly, electrical breakdown damage is able to be healed at high healing efficiency (90%), which overcomes the classical dilemma between insulation and healability. The study provides a new way to enhance the performance and reliability of actuator polymer dielectrics, especially at high electric field intensity. • Fluorine substitution is found to promote healability of silicone. • Not only mechanical damage, but also electrical breakdown damage can be healed. • The electrical and mechanical properties are comparable with commercial silicone. • Effects including fluorine content and crosslinking on properties were studied.

Achieving Excellent Energy Storage Properties in Fine‐Grain High‐Entropy Relaxor Ferroelectric Ceramics

AbstractABO3‐type high‐entropy relaxor ferroelectric ceramics have rarely been studied in energy storage capacitor owing to easy formation of impurity phase. In this work, single phase (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3‐xmol%PbO high‐entropy ceramics are fabricated and investigated. The optimal composition of x = 2.0 shows a remarkable comprehensive energy storage performance with high recoverable energy density Wrec = 8.2 J cm–3, ultrahigh efficiency η = 92.2%, excellent temperature stability (Wrec = 4.4 J cm‐3 ± 4%, η = 91% ± 3% within the range of 25–120 °C), and ultrafast discharge rate t0.9 = 5.9 µs. Three key factors, low remnant polarization Pr originating from high‐entropy enhanced relaxation degree, high maximum polarization Pm due to special electronic structure of Pb ion, and high electrical breakdown strength Eb stemming from small grain size, are responsible for the improved energy storage properties. These results provide a novel strategy of developing high‐entropy ceramics to optimize electrical performances including energy storage property.

Outstanding discharge energy density and efficiency of the bilayer nanocomposite films with BaTiO3-dispersed PVDF polymer and polyetherimide layer

Dielectric polymer nanocomposite films have been widely studied because of their high polarization and electric breakdown strength, leading to high discharge energy density (Ud). However, nanocomposites with high Ud often show low discharge energy efficiency (η). In order to achieve both high Ud and η simultaneously, a series of novel bilayer polymer nanocomposite films composed of pure polyetherimide (PEI) layer and BaTiO3-dispersed poly(1,1-difluoroethylene) (BT/PVDF) layer were prepared by hot-pressing method in this work. The bilayer composites exhibit high η > 84% at 600 MV⋅m−1, which are much larger than most reported values (η < 70%). Specially, the highest η of 84.48% and Ud of 8 J·cm−3 at 600 MV·m−1 were obtained for the bilayer films composed of PEI and 3 vol% BT/PVDF layers, which is promising for pulsed power applications.

High Energy Storage Performance in Ba0.85Ca0.15Zr0.1Ti0.9O3‐ZnO Hybrid Perovskite Solid Solution Thin Films

AbstractRelaxor property plays a key role in determining energy storage performance of dielectric capacitor. The usual method to improve relaxor property is to form substitutional solid solution. Here an unusually substitutional and interstitial hybrid perovskite solid solution 0.8(Ba0.85Ca0.15Zr0.1Ti0.9O3)‐0.2ZnO (BCZT:Zn) is designed, where one Zn2+ occupies B‐site and two Zn2+ share one A‐site of perovskite structure, and fabricated its epitaxial thin films. Compared to BCZT films, BCZT:Zn films have increased c/a ratio which leads to enhanced maximum polarization Pmax, wide band gap therefore high electrical breakdown strength EBDS, and enhanced relaxor degree thus suppressed remanent polarization Pr. As the results, dramatically improve energy storage property with the recoverable energy storage density Wrec of 75.9 J cm−3 and the energy storage efficiency η of 76.7% are obtained in BCZT:Zn films. This work not only provides a high performance relaxor ferroelectric material, but also impacts some new thinking to optimize die/ferro/piezoelectric properties by forming hybrid solid solutions.

Excellent Energy Storage Performance in Bi(Fe0.93Mn0.05Ti0.02)O3 Modified CaBi4Ti4O15 Thin Film by Adjusting Annealing Temperature.

Dielectric capacitors with ultrahigh power density are highly desired in modern electrical and electronic systems. However, their comprehensive performances still need to be further improved for application, such as recoverable energy storage density, efficiency and temperature stability. In this work, new lead-free bismuth layer-structured ferroelectric thin films of CaBi4Ti4O15-Bi(Fe0.93Mn0.05Ti0.02)O3 (CBTi-BFO) were prepared via chemical solution deposition. The CBTi-BFO film has a small crystallization temperature window and exhibits a polycrystalline bismuth layered structure with no secondary phases at annealing temperatures of 500–550 °C. The effects of annealing temperature on the energy storage performances of a series of thin films were investigated. The lower the annealing temperature of CBTi-BFO, the smaller the carrier concentration and the fewer defects, resulting in a higher intrinsic breakdown field strength of the corresponding film. Especially, the CBTi-BFO film annealed at 500 °C shows a high recoverable energy density of 82.8 J·cm−3 and efficiency of 78.3%, which can be attributed to the very slim hysteresis loop and a relatively high electric breakdown strength. Meanwhile, the optimized CBTi-BFO film capacitor exhibits superior fatigue endurance after 107 charge–discharge cycles, a preeminent thermal stability up to 200 °C, and an outstanding frequency stability in the range of 500 Hz–20 kHz. All these excellent performances indicate that the CBTi-BFO film can be used in high energy density storage applications.

Electrode material effect on electromechanical properties of dielectric elastomers in different ambient humidity

The electromechanical properties of dielectric elastomers (DEs) are surely affected by the ambient humidity and electrode materials. In this article, under a varying ambient humidity, the dielectric constant, electromechanical deformation and electrical breakdown strength of Very-High-Bond (VHB) 4905 elastomer with different electrode materials are experimentally investigated. Four common electrode materials, including carbon grease, carbon powder, conductive adhesive, and conductive silicone rubber, are involved. Experimental results directly show that the electromechanical deformation and electrical breakdown strength of DEs with different electrode materials have distinct sensitivity to humidity. Under a condition of diverse humidity, the VHB film with carbon grease is found to generate the largest voltage-induced deformation, while a high electrical breakdown strength is induced by the electrode material of carbon powder.

Hierarchical tungsten-copper composite reinforced by a concrete skeleton of particulate and fibrous tungsten with coherent Cr precipitates in the copper matrix

The substitution of a precipitation-hardenable alloy of Cu-0.5wt.%Cr for the widely adopted pure Cu has been proposed for infiltration into the pre-sintered concrete skeleton of particulate and fibrous W. By the reinforcement of a concrete skeleton of particulate and fibrous W along with coherent Cr precipitates in the Cu matrix, the composite exhibited superior comprehensive properties. Specifically, the proposed composite here exhibited a high tensile strength of 601.2 MPa improved by 22.7%, a low friction coefficient of 0.567 decreased by 27.3% and high electrical breakdown strength of 9.07 × 107 V/m increased by 101.5%. Notably, due to the precipitation of the coherent Cr particles to lower the solute content in the Cu matrix, the composite exhibited rather good electrical conductivity of 51.4%IACS. The proposed strategy by infiltration of precipitation-hardenable Cu-based alloys into the W skeleton here provides a new clue for the microstructure design and performance enhancement of novel WCu composites.

Diamond/GaN HEMTs: Where from and Where to?

Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility transistors, the relatively low thermal conductivity of the material induces the appearance of localized hotspots that degrade the devices performance and compromise their long term reliability. On the search of effective thermal management solutions, the integration of GaN and synthetic diamond with high thermal conductivity and electric breakdown strength shows a tremendous potential. A significant effort has been made in the past few years by both academic and industrial players in the search of a technological process that allows the integration of both materials and the fabrication of high performance and high reliability hybrid devices. Different approaches have been proposed, such as the development of diamond/GaN wafers for further device fabrication or the capping of passivated GaN devices with diamond films. This paper describes in detail the potential and technical challenges of each approach and presents and discusses their advantages and disadvantages.

Enhancement of Energy-Storage Density in PZT/PZO-Based Multilayer Ferroelectric Thin Films.

PbZr0.35Ti0.65O3 (PZT), PbZrO3 (PZO), and PZT/PZO ferroelectric/antiferroelectric multilayer films were prepared on a Pt/Ti/SiO2/Si substrate using the sol–gel method. Microstructures and physical properties such as the polarization behaviors, leakage current, dielectric features, and energy-storage characteristics of the three films were systematically explored. All electric field-dependent phase transitions, from sharp to diffused, can be tuned by layer structure, indicated by the polarization, shift current, and dielectric properties. The leakage current behaviors suggested that the layer structure could modulate the current mechanism, including space-charge-limited bulk conduction for single layer films and Schottky emission for multilayer thin films. The electric breakdown strength of a PZT/PZO multilayer structure can be further enhanced to 1760 kV/cm, which is higher than PZT (1162 kV/cm) and PZO (1373 kV/cm) films. A recoverable energy-storage density of 21.1 J/cm3 was received in PZT/PZO multilayers due to its high electric breakdown strength. Our results demonstrate that a multilayer structure is an effective method for enhancing energy-storage capacitors.

Enhanced dielectric response of ternary polymeric composite films via interfacial bonding between V2C MXene and wide-bandgap ZnS

Increasing the dielectric constant of polymer/sulfide ceramic composites by using wide-bandgap semiconducting sulfide ceramic fillers like ZnS is difficult because of their low interface polarization. To increase the dielectric constant, in this study, ternary polymer-based composite films were designed and fabricated using a hybrid filler consisting of shell-like ZnS particles and core-like V2C MXene particles. First, V2C MXene with a multi-layered structure was synthesized from the simplest raw materials followed by the in-situ hydrothermal growth of ZnS particles around the V2C particles. Then, binary polymer/ZnS and ternary polymer/V2C–ZnS composites were fabricated, and their dielectric, conductive, and electrical breakdown properties were investigated. Finally, the effect of interfacial bonding between the V2C and ZnS phases was investigated by density functional theory calculations, and the contribution of V2C/ZnS interfacial bonding to the higher dielectric constant of the ternary composites than that of the binary composites was explained. The ternary composites exhibited balanced electrical properties suitable for energy storage applications. The ternary composite with 10 wt% hybrid filler loading exhibited a high dielectric constant of ~52, a low dielectric loss of ~0.11 at 100 Hz, and a high electrical breakdown strength of ~202 MV m−1. This study paves the way for the facile fabrication of high-performance composite dielectrics for application in advanced capacitors.

Temperature dependence of β-Ga2O3 heteroepitaxy on c-plane sapphire using low pressure chemical vapor deposition

β-Ga2O3 has drawn significant attention for power electronics and deep ultraviolet (UV) photodetector applications owing to its wide bandgap of ~4.4–4.9 eV and high electric breakdown strength of ~7–8 MV/cm. Growth of β-Ga2O3 epitaxial thin films with high growth rate has been recently reported using low pressure chemical vapor deposition (LPCVD) technique. In this work, we have investigated the effect of growth temperature on β-Ga2O3 films grown on c-plane sapphire substrates using LPCVD. We performed growths by varying temperatures from 800 °C to 950 °C while keeping all other growth parameters (Ar/O2 gas flow rates, growth pressure, and Gallium precursor to substrate distance) constant. Optical, structural, and surface characterizations are performed to determine the thickness, bandgap, phase purity, crystal orientation, and crystalline quality of the grown thin films. Amorphous islands of Ga2O3 are observed at growth temperature of 800 °C while continuous and crystalline (−201) oriented β-Ga2O3 thin films are achieved for growth temperatures of 850–950 °C. Crystallinity of the films is found to improve with increase in growth temperature with a minimum rocking full width at half maximum of 1.52º in sample grown at 925 °C. For all the samples grown at and above 875 °C, transmittance measurements revealed an optical bandgap of ~4.77–4.80 eV with high growth rate of ~6 µm/h.

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives.

Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge–discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength. Polymer dielectric capacitors offer high power/energy density for applications at room temperature, but above 100 °C they are unreliable and suffer from dielectric breakdown. For high-temperature applications, therefore, dielectric ceramics are the only feasible alternative. Lead-based ceramics such as La-doped lead zirconate titanate exhibit good energy storage properties, but their toxicity raises concern over their use in consumer applications, where capacitors are exclusively lead free. Lead-free compositions with superior power density are thus required. In this paper, we introduce the fundamental principles of energy storage in dielectrics. We discuss key factors to improve energy storage properties such as the control of local structure, phase assemblage, dielectric layer thickness, microstructure, conductivity, and electrical homogeneity through the choice of base systems, dopants, and alloying additions, followed by a comprehensive review of the state-of-the-art. Finally, we comment on the future requirements for new materials in high power/energy density capacitor applications.

Soft dielectric elastomer tubes in an electric field

Soft dielectric elastomers with high relative permittivity, very low modulus and high electric breakdown strength have emerged as promising materials for various applications as sensors, actuators and in energy harvesting and soft robotics. We study the intricate deformation behaviour of a soft dielectric elastomer tube of finite length and closed ends, that carries a dead load, is internally pressurised by an injected fluid and has a high electric potential applied across its walls. As for soft tubes in the absence of a potential, this electro-hyperelastic problem involving very large deformations, exhibits a multitude of possibilities, including homogeneous deformation, inhomogeneous bifurcation, snap-through instabilities and post bifurcation behaviour in the form of propagation of axisymmetric bulges. We develop a coupled Finite Element procedure for the situation where the domains of the mechanical and electrostatic problems coincide. The procedure can handle volume flow rate controlled electro-elastic problems. We use it to study the many aspects of the deformation behaviour and limitations placed by competing failure mechanisms on practical utilisation of the large areal strains and axial actuations that can be produced. If electrical breakdown can be avoided by ingenious design of loading sequences, the large volume increase in the tube due to the triggering of instabilities can be harnessed and has far-reaching technological implications.

Simultaneously achieving ultrahigh energy density and power density in PbZrO3-based antiferroelectric ceramics with field-induced multistage phase transition

Abstract Ceramic-based dielectric capacitors are the heart components of advanced power electronic devices and pulsed power systems to store and release electrical energy due to excellent charge-discharge properties. However, the unsatisfactory energy-storage density has limited their practical applications. Therefore, it is still a significant challenge to develop dielectric ceramics with further improved energy density and power density to satisfy the growing demands. Herein, high energy density and power density in a dielectric ceramic is achieved in(Pb0.94La0.04)(ZrxSn0.99−xTi0.01)O3 antiferroelectric (AFE) ceramics by constructed multistage phase transition (MPT) and realized high densification. All the ceramics possess large polarization response and high electric breakdown strength (BDS) under the effect of MPT and high densification, respectively. Consequently, a superior recoverable energy density of 13 J/cm3 and an ultrahigh power density of 324.8 MW/cm3 together with a giant current density of 1910.8 A/cm2 are realized simultaneously due to the synergistic effect of MPT and high densification. These excellent performances indicate that the studied ceramics have the potential to meet the growing demands and be applied for dielectric capacitors in advanced power electronic devices and pulsed power systems.

Enhancement of dielectric breakdown strength and energy storage of all-polymer films by surface flattening

All-organic dielectric films with the significant advantage of easy processing are highly desired in electronic and electric industry. As dielectric energy storage materials, improvement of their dielectric permittivity and electric breakdown strength is a long-standing work. Polytetrafluoroethylene (PTFE) films possess excellent high temperature properties but their electric breakdown strength is largely dependent on the surface flattness. Especially, interconnecting fiber structure tends to form during calcination when an ultrathin film is fabricated through a coating process. Herein, the surface of the PTFE films was flattened with epoxy resin. A high electric breakdown strength of 555 kV/mm, which is 134% of the pure PTFE film, and an improved dielectric permittivity of 2.3 have been achieved for the PTFE film immersed in 0.5 wt% epoxy solution at room temperature. It displays a discharged energy density of 3.58 J/cm3 (2.2 times of the pure PTFE film) with 98% discharge efficiency. The achieved high electric breakdown strength is owing to the reduced local electric field at the interface between film surface and electrode according to the simulation results. Besides, it also achieved a high discharged energy density of 1.93 J/ cm3 at 150 °C with 99% efficiency. Therefore, using organic to flatten the surface of polymer films has proved significantly effective in improving the dielectric energy storage performance.

Development of High Dielectric Electrostrictive PVDF Terpolymer Blends for Enhanced Electromechanical Properties.

Electroactive polymers with high dielectric constants and low moduli can offer fast responses and large electromechanical strain under a relatively low electric field with regard to theoretical driving forces of electrostriction and electrostatic force. However, the conventional electroactive polymers, including silicone rubbers and acrylic polymers, have shown low dielectric constants (ca. < 4) because of their intrinsic limitation, although they have lower moduli (ca. < 1 MPa) than inorganics. To this end, we proposed the high dielectric PVDF terpolymer blends (PVTC-PTM) including poly(vinylidene fluoride-trifluoroethylene-chlorofluoro-ethylene) (P(VDF-TrFE-CFE), PVTC) as a matrix and micelle structured poly(3-hexylthiophene)-b-poly(methyl methacrylate) (P3HT-b-PMMA, PTM) as a conducting filler. The dielectric constant of PVTC-PTM dramatically increased up to 116.8 at 100 Hz despite adding only 2 wt% of the polymer-type filler (PTM). The compatibility and crystalline properties of the PVTC-PTM blends were examined by microscopic, thermal, and X-ray studies. The PVTC-PTM showed more compatible blends than those of the P3HT homopolymer filler (PT) and led to higher crystallinity and smaller crystal grain size relative to those of neat PVTC and PVTC with the PT filler (PVTC-PT). Those by the PVTC-PTM blends can beneficially affect the high-performance electromechanical properties compared to those by the neat PVTC and the PVTC-PT blend. The electromechanical strain of the PVTC-PTM with 2 wt% PTM (PVTC-PTM2) showed ca. 2-fold enhancement (0.44% transverse strain at 30 Vpp μm−1) relative to that of PVTC. We found that the more significant electromechanical performance of the PVTC-PTM blend than the PVTC was predominantly due to the electrostrictive force rather than electrostatic force. We believe that the acquired PVTC-PTM blends are great candidates to achieve the high-performance electromechanical strain and take all benefits derived from the all-organic system, including high electrical breakdown strength, processibility, dielectrics, and large strain, which are largely different from the organic–inorganic hybrid nanocomposite systems.

Mechanical, dielectric and thermal properties of polyimide films with sandwich structure

With the development of high-frequency and high-speed flexible circuit boards, there are growing demands for low dielectric constant materials with high mechanical and electric breakdown strength. Herein, a novel sandwich structure is successfully fabricated using fluorinated graphene/polyimide (FG/PI) composite film as a dense outer surface layer and porous PI film as the middle layer. The middle porous layer lead to the ultra low dielectric constant. The presence of FG/PI layers resulted in the increase of mechanical and dielectric breakdown performance compared to that of porous PI. Especially, the three-layer FG/ PI film showed a tensile strength of 65.76 MPa, a tensile modulus of 2.96 GPa, a characteristic breakdown strength of 170.49 kV/mm, a dielectric constant of 1.92, and a dielectric loss of less than 0.003. Therefore, the sandwich structure PI film is a highly prospective candidate as flexible circuit substrates for electronics and microelectronics devices.

High-temperature energy storage properties in polyimide-based nanocomposites filled with antiferroelectric nanoparticles

Inorganic ferroelectric filler/polymer nanocomposites combining large maximum electric displacement (Dmax) of ferroelectric materials with good flexibility and high electric breakdown strength (Eb) of the polymers are regarded as the most promising materials for preparing flexible dielectric capacitors with superior energy storage properties. Besides dielectric capacitors are always faced with high temperature environment in many application cases, and thus the applicability of high temperature is also highly desired. To develop nanocomposite-based dielectric capacitors with superior energy storage properties in a wide temperature range, in this study, we synthesize Pb0.97La0.02(Zr0.5Sn0.38Ti0.12)O3 (PLZST) antiferroelectric nanoparticles (NPs) with larger Dmax and smaller remnant electric displacement (Dr) in comparison with ferroelectric nanoparticles and disperse them into polyimide (PI) polymer matrix with good temperature stability. The results indicate that by adjusting reasonably the PLZST filler content, in a wide temperature range of 20–120°C, 7wt.% PLZST/PI nanocomposite exhibits slim electric displacement-electric field hysteresis loops and low Dr, and thus the discharge energy density and energy efficiency are always higher than 4J/cm3 and 90%, respectively. These indicate this nanocomposite is a good candidate material for developing flexible dielectric capacitors applicable in high temperature environment.

Recent advances in rational design of polymer nanocomposite dielectrics for energy storage

Abstract Polymer nanocomposites dielectrics have attracted increasing attention for electric energy storage applications in recent years due to their enhanced dielectric performance by combining the high permittivity of nanoparticles and the high electrical breakdown strength of polymer matrix. Herein we present a review of the recent advances in the modelling of dielectric energy storage and model-based rational design of polymer nanocomposite dielectrics. The synthesis strategies and dielectric property behaviors of polymer nanocomposite dielectrics are also discussed. In particular, this review focuses on key strategies and analytical models for substantial improvements in energy density of composite dielectrics including interfacial design, microstructural engineering and new high-dielectric filler materials. By applying machine learning techniques in conjunction with the analytical models, new designs have emerged. To demonstrate the practical applications of polymer nanocomposite dielectrics, a summary is presented of some recent examples of scale-up production of energy storage devices in electrical vehicles, pulsed weapons systems and power electronics. Finally, challenges and new application opportunities of polymer nanocomposite dielectrics are discussed.

Mechanical, Dielectric, and Thermal Attributes of Polyimides Stemmed Out of 4, 4’–Diaminodiphenyl Ether

Several kinds of polyimide (PI) films stemmed out of 4, 4’–diaminodiphenyl ether, as well as various structurally various aromatic dianhydride, were prepared. The films’ mechanical, dielectric, and dynamic mechanical attributes were put under investigation. According the findings, the PI films’ performance is significantly different as a result of their diverse structure. PI’s dielectric constant and dielectric loss tangent of abides by the increasing order below: PMDA-PI&gt;BTDA-PI&gt;BPDA-PI. Moreover, the electric breakdown strength of BTDA-PI (478.90 kV/mm) presents a lot higher value compared to the one PMDA-PI (326.80 kV/mm) and BPDA-PI (357.07 kV/mm). In particular, BTDA-PI film possesses high electric breakdown strength about 478.90 kV/mm. In addition, PI’s glass transition temperature (Tg) are, respectively, 276 °C (BTDA-PI), and 290 °C (BPDA-PI), as well as 302 °C (PMDA-PI). Therefore, in virtue of their various structures and performances, practical applications of PI films can exert significant role in the electronics and microelectronics industries.