Electric Strength Research Articles

Electrical safety assessment of a prototype device for electromagnetic stimulation of the ear in patients with tinnitus.

<b><br>Aim:</b> The aim of the study was to evaluate the results of electrical safety results of a prototype electromagnetic ear stimulation device in patients with tinnitus.</br> <b><br>Material and methods:</b> The electrical safety tests of the prototype device for electro- and magnetostimulation of the hearing organ were carried out at the Center for Attestation and Certification Tests in Gliwice. The tests concerned selected parameters including the PN-EN standard.</br> <b><br>Results:</b> Safety studies of the prototype electrical stimulation device for the ear in patients with tinnitus were necessary to perform the planned further preclinical studies. Obtained results regarding: identification and labeling of the device; protection against electric shock; checking protective earthing, functional earthing and potential equalization; checking the leakage current and auxiliary currents of the patient; checking the distances through the solid insulation and the use of thin insulating spacers; checking the electrical strength of the device insulation; checking protection against mechanical hazards of the device; checking the risk associated with surfaces, corners and edges, and checking the protection against excessive temperatures and other threats comply with the standard PN-EN.</br> <b><br>Conclusions:</b> No risk to the patient and medical staff. Tests of protection against mechanical hazards of the device have shown that the only movable part whose contact with the patient could cause an unacceptable risk is the fan installed inside the housing.</br&gt.

Silicon/carbon nanotubes anode for lithium-ion batteries: Synthesis, interface and electrochemical performance

Silicon/carbon composite has been a promising anode material for lithium-ion batteries (LIBs). Carbon nanotubes (CNTs) possess high electrical conductivity, specific area, and mechanical strength, holding great potential for constructing advanced Si/C anode materials. However, the unstable interface and tricky synthesis processes hinder practical applications of Si/CNTs anode. In this work, we develop a one-step method to prepare Si/CNTs composite by magnesium reduction of SiO2 mixed with CNTs. The interface between Si nanoparticles and CNTs upon the weight ratio of SiO2 to CNTs and their influences on the electrochemical performances of Si/CNTs composite have been systematically studied. The Si nanoparticle partly reacts with CNTs and forms Si-C bonds in the interface when the mass ratio of SiO2 to CNTs is above 1.5. The electrochemical performance of this three-phase heterostructure (Si/CNTs-2) are significantly improved due to the Si-C chemical bonding. A high initial reversible capacity of 1100.2 mAh g−1 at 0.2 A g−1 is obtained, and the capacity of 922.4 mAh g−1 remains after 200 cycles with a high capacity retention of 83.3 %. The rate capability is excellent and the capacity is 797 mAh g−1 at 5 A g−1 and remains 612.3 mAh g−1 after 1000 cycles. The interfacial design of Si/CNTs composite provides guidance to prepare high- performance Si/C composite anode.

Grafting of voltage stabilizer onto EPDM surface and its inhibition effect on the breakdown of EPDM/XLPE interface

Surface discharge on the EPDM/XLPE interface is threatening the safe operation of power cable system and limiting the further improvement of its voltage level. To improve the electrical strength of EPDM/XLPE interface, the surface of EPDM was modified by grafting of voltage stabilizer 4-allyloxy-2-hydroxybenzophenone (AOHBP) based on liquid-phase impregnation and subsequent free radical grafting reaction thermally initiated by DCP. EPDM samples were modified by mixed reagents of DCP and AOHBP with different mass ratios of 1:2, 1:3 and 1:4, respectively. The SEM observation and XRD analysis results indicate that the crystals of AOHBP with a uniform distribution are covered on the surface of EPDM during the sample preparation process and then dissolved after extraction by acetone. The FTIR and ATR results show that the AOHBP molecules are successfully grafted onto the surface of EPDM samples, but there remain a lot of ungrafted reagent molecules on the surface of EPDM before solvent extraction. The grafting rate of AOHBP increases with the proportion of DCP in the mixed reagents. As for the unextracted modified EPDM samples, both the AC and DC breakdown voltage of the EPDM/XLPE interface are increased compared with pure EPDM, and further increased after the ungrafted molecules are extracted because the effect of voltage stabilizer on scavenging high-energy electrons is more efficiently utilized at a smoother interface. The interface breakdown voltage of the sample modified with 1:2 mass ratio of DCP/AOHBP mixed solution is the highest because of its highest grafting rate of voltage stabilizer. This work has proposed a new technical path to improve the electrical aging resistance of polymer insulating surface.

Increasing the Electrical Strength and Operation Stability of a Small-Sized Ion Accelerator

Increasing the Electrical Strength and Operation Stability of a Small-Sized Ion Accelerator

A high strength and high electrical conductivity copper based composite enhanced by graphene and Al2O3 nanoparticles

The rapid development of electrical and electronic engineering requires to further surmount the trade-off between the electrical conductivity and strength of Cu matrix composite. In this study, the surface of Cu–Al2O3 powder is selective for carbon sources, and only α-naphthol can prepare graphene. Graphene and Al2O3 particles are simultaneously incorporated into Cu matrix by hot-press sintering Cu–Al2O3 powders by internal oxidation coated with in-situ grown graphene. This composite exhibits a good combination of strength and conductivity (600 MPa of ultimate tensile strength and 81.7 % IACS of electrical conductivity) due to synergistic effect of graphene and Al2O3 particles. This composite fabricated by such synergistic more effectively retains the microstructure induced by plastic deformation during the cold-rolling process. Both graphene and Al2O3 particles uniformly distribute in Cu matrix. Coherent Al2O3 particles and graphene in situ grown can be well enhance to Orowan looping mechanism effect, and the addition of graphene in Cu matrix composite with Al2O3 particles can improve dislocation strengthening and dispersion strengthening at the same time. Our study provides an effective route to achieve simultaneously high strength and conductivity of Cu matrix composites.

Muti-Filler Composites Reinforced with Multiwalled Carbon Nanotubes and Chopped Carbon Fibers for the Bipolar Plate of Fuel Cells

To improve the conductivity and flexural strength of bipolar plates for proton-exchange membrane fuel cells, multi-filler-reinforced composites were prepared using graphite, multiwalled carbon nanotubes (MWCNTs), chopped carbon fibers (CCFs), and phenolic resin (PF). The effects of CCF content (0–6 wt.%) and MWCNT content (0–8 wt.%) on the flexural strength, electrical conductivity, interfacial contact resistance (ICR), density, hydrophobicity, and corrosion behavior of the composites were investigated. Results showed that the addition of a small number of CCFs (≤4 wt.%) effectively improved the flexural strength but slightly reduced the electrical conductivity and increased the ICR of the graphite/PF/CCF composites. Further addition of MWCNTs (≤6 wt.%) significantly improved the electrical conductivity and ICR of the graphite/PF/CCF/MWCNT composites, while maintaining high flexural strength. When the composites were filled with 4 wt.% CCFs and 2 wt.% MWCNTs, their electrical conductivity, flexural strength, ICR under 1.38 MPa, and contact angle were 272.8 S/cm, 43.1 MPa, 1.19 mΩ·cm2, and 101.5°, respectively. Compared to unreinforced composites, the electrical conductivity was reduced by 27.2%, the flexural strength was increased by 65.1%, and the composite possessed favorable hydrophobicity as well as corrosion behavior. This work reveals that CCFs and MWCNTs can effectively cooperate to improve composites’ electrical and flexural strength properties.

Research of MXenes and Their Applications in Sensors and Batteries

MXene, a novel two-dimensional material class, demonstrates significant potential across diverse applications such as electrochemical heavy metal detection, pressure sensor active material, and sodium battery composites. MXene-based sensors, in the realm of heavy metal detection, exhibit high sensitivity and selectivity, which are vital in monitoring and controlling environmental pollution. These sensors utilize MXene's distinct conductive and surface properties, facilitating efficient and precise detection of heavy metals, including lead, mercury, and cadmium. In pressure sensors, MXene contributes to enhanced performance owing to its superior electrical conductivity and mechanical strength, allowing the creation of sensitive and robust sensors apt for cutting-edge applications in robotics, wearable technology, and IoT devices. Furthermore, MXene composites in sodium batteries lead to improved battery performance in energy storage. The high conductivity and electrochemical stability of MXene, coupled with its sodium ion hosting capability, render it an optimal material for boosting sodium battery capacity and cyclability. This progress holds immense importance in developing sustainable and efficient energy storage solutions. MXene's versatility and exceptional attributes continue to propel innovation in various fields, including environmental monitoring, energy storage, and sensor technology.

THE CHALLENGING SCALP–ELECTRODE INTERFACE AND THE EVOLUTION OF MATERIALS AND ELECTRODE INTEGRATED ICTs FOR ELECTROENCEPHALOGRAPHY

Electroencephalography (EEG) is a non-invasive technique used to measure the electrical activity of the brain. The use of EEG is very important for the diagnosis of traumatic brain events and mental states such as injury, stroke, depression and many others including the COVID-19 brain fog syndrome. The quality of EEG signals largely depends on the nature of the interface between the surface of the electrode material and the surface of the scalp from where the electrical brain signals are acquired. The scalp surface is composed of an epidermic substrate with hair, grease, dirt, dandruff, skin peels and eventually many different hair products. The electrodes must combine several properties including electrical conductivity, mechanical strength, biocompatibility and corrosion resistance. They also must be manufactured with shapes designed to overcome the inherently complex nature of the scalp–electrode interface. This review reports the latest advances in the design of materials, surface coatings, conductive gels and information and communication technologies being developed to increase the quality of measurement of brain electrical signals in EEG protocols.

Модификация диффузионных бор- и алюминийсодержащих слоев электронно-пучковой обработкой

The article presents testing results of electron beam processing (EBP) modes applied on the diffusion layers based on boron and aluminum produced on the surface of steel 20. An ion current feedback loop in the accelerating gap in a modernized plasma electron source allows increasing the beam generation control and the electrical strength of the accelerating gap. This ensures sample surface processing at a specified temperature. In order to ensure the EBP process stability, it is proposed to preheat the surface to a temperature range of 400-700℃ by pulses with a controlled current. Further modification of the diffusion layers is conducted on the surface at a temperature of around 1900℃. Ensuring this temperature range demands the discharge current within the range of 20 - 150A during a single pulse with a duration of 950 μs. The total number of pulses is three and the interval between them is 3 seconds. These processing modes lead to a structural transformation of the diffusion layer to a depth of more than 150 μm and to a significant microhardness increase. The approved EBP modes can be recommended as a promising alternate approach of the combined modification technologies of diffusion layers based on boron and aluminum.

Synthesis and Characterization of Bisphenol-C Epoxy Crotonate and Its Fiber-Reinforced Composites

Bisphenol-C epoxy crotonate resin was synthesized by reacting 8.09g epoxy resin of bisphenol- C, and 2.15g crotonic acid using 25 mL 1,4-dioxane as a solvent, and 1 mL triethylamine as a catalyst at reflux temperature for 1-6 h. Solid epoxy crotonate (ECCR) is highly soluble in common organic solvents. ECCR was characterized by its acid (24.5-1.5 mg KOH/g) and hydroxyl (504.5-678.4 mg KOH/g) values. The structure of ECCR is supported by FTIR and 1HNMR spectroscopic methods. A DSC endothermic transition at 229oC indicated melting followed by thermal polymerization of ECCR. ECCR is thermally stable up to 320oC and follows three-step degradation kinetics. The first step followed first-order degradation kinetics, while the second and third steps followed one-half-order degradation kinetics. High values of kinetic parameters suggested the rigid nature of the crosslinked resin. Jute-, Glass- and Jute-natural fiber-ECCR composites showed moderate tensile strength, flexural strength, electric strength, and volume resistivity due to the rigid nature and poor interfacial adhesion of the composites. J-ECCR and G-ECCR composites showed high water absorption tendency and excellent hydrolytic stability against water, 10% aq. HCl and 10% aq. NaCl and even in boiling water. Mechanical and electrical properties and water absorption tendency of the composites indicated their usefulness as low load-bearing housing and insulating materials. They can also be utilized in harsh environmental conditions.

Synergistic effect of positive temperature coefficient and thermally conductive micro‐nano fillers on electrical and thermal properties of epoxy resin

AbstractThis study investigates the effect of positive temperature coefficient (PTC) fillers, i.e., barium strontium titanate (BST‐60) and nano hexagonal boron nitride (h‐BN) fillers, on thermal and dielectric insulation properties of epoxy (EP). The electrical resistivity, DC breakdown strength, space charge, thermal conductivity, thermogravimetric analysis, and glass transition temperature (Tg) of EP composites were measured. Results indicate that, below curie temperature, the EP composites containing 0.5 and 1 wt% of BST and 5 wt% of h‐BN have superior electrical resistivity, breakdown strength, and thermal conductivity. However, above curie temperature, the EP composites containing 2 and 2.5 wt% of BST and 5 wt% of h‐BN have superior insulation properties than the pure EP and other composites. While the thermal properties of EP improve with an increase in h‐BN loading to 10 wt%, its dielectric properties are slightly compromised due to the presence of tiny defects in the composite material. It is hypothesized that the BST‐60 suppresses the negative temperature coefficient effect (NTC) of EP by regulating the electrical resistivity above the curie point, whereas nano h‐BN enhances the thermal conductivity of EP by constructing a heat dissipation path. The proposed mechanism for charge dynamics along with heat conduction‐dissipation explains the fillers' behavior at different temperatures.Highlights Analysis of epoxy composites with polydopamine‐modified BST and h‐BN fillers. PTC fillers are used to mitigate the negative temperature effect of epoxy. Optimal fillers wt% improves dielectric and thermal properties. This study shows that optimized epoxy composites can be used for packaging.

Effect of Secondary Phase on Electroless Ni Plating Behaviour of Super Duplex Stainless Steel SAF2507 for Advanced Li-Ion Battery Case.

The development of Li-ion battery cases requires superior electrical conductivity, strength, and corrosion resistance for both cathode and anode to enhance safety and performance. Among the various battery case materials, super duplex stainless steel (SDSS), which is composed of austenite and ferrite as two-phase stainless steel, exhibits outstanding strength and corrosion resistance. However, stainless steel, which is an iron-based material, tends to have lower electrical conductivity. Nevertheless, nickel-plating SDSS can achieve excellent electrical conductivity, making it suitable for Li-ion battery cases. Therefore, this study analysed the plating behaviour of SDSS plates after nickel plating to leverage their exceptional strength and corrosion resistance. Electroless Ni plating was performed to analyse the plating behaviour, and the plating behaviour was studied with reference to different plating durations. Heat treatment was conducted at 1000 °C for one hour, followed by cooling at 50 °C/s. Post-heat treatment, the analysis of phases was executed using FE-SEM, EDS, and EPMA. Electroless Ni plating was performed at 60-300 s. The plating duration after the heat treatment was up to 300 s, and the behaviour of the materials was observed using FE-SEM. The phase analysis concerning different plating durations was conducted using XRD. Post-heat treatment, the precipitated secondary phases in SAF2507 were identified as Sigma, Chi, and CrN, approximating a 13% distribution. During the electroless Ni plating, the secondary phase exhibited a plating rate equivalent to that of ferrite, entirely plating at around 180 s. Further increments in plating time displayed growth of the plating layer from the austenite direction towards the ferrite, accompanied by a reduced influence from the substrate. Despite the differences in composition, both the secondary phase and austenite demonstrated comparable plating rates, showing that electroless Ni plating on SDSS was primarily influenced by the substrate, a finding which was primarily confirmed through phase analysis.

Excellent energy storage performance of lead-based antiferroelectric ceramics via enhancing dielectric breakdown mechanism

Lead-based antiferroelectric (AFE) material with high power density has received extensive attention for potential applications in the energy storage devices. Nevertheless, the presence of a secondary phase reduces the band gap and concentrates a significant localized electric field at the center of the tips of both secondary phases, leads to a poor breakdown electric strength (Eb). Hence, we designed high Eb of (Pb1-1.5xSmx)(Zr0.995Ti0.005)O3 ceramics with high energy performance via enhancing dielectric breakdown mechanism by restraining secondary phase. Density functional theory calculations reveal that the valence and conduction bands of secondary phase are in close proximity to the Fermi level, indicating the smaller band gap of secondary phase is unable to withstand the concentration of local electric fields in this samples, thus leading to obtain a poor Eb. UV–vis absorption spectra experiments demonstrate that the overall band gap increases due to the A-site Sm modification strategy, effectively reducing the secondary phase and resulting in elevated levels of Eb. As a consequence, Eb is remarkably improved from 350 kV/cm into 540 kV/cm with increasing Sm3+ content. A record-high Eb of 520 kV/cm and high recoverable energy storage density of 12.9 J/cm3 (energy efficiency of 77.1 %) are achieved in (Pb0.91Sm0.06)(Zr0.995Ti0.005)O3 (PS6ZT) ceramics by tape-casting method. Concerning the performance of pulse charge–discharge, ultrahigh discharge energy density of 8.5 J/cm3 and excellent power density of 188.53 MW/cm3 are achieved in PS6ZT ceramics. Moreover, outstanding stability behavior with a broad frequency range of 1∼140 Hz and a broad temperature range of 20–120 ℃ are obtained. These results show that enhancing Eb mechanism will be provided a potential option to enhanced energy density for PbZrO3-based AFE ceramics.

Giant vesicles form in physiological saline and encapsulate pDNA by the modified electroformation method

Giant vesicles (GVs) are used to study the structures and functions of cells and cell membranes. Electroformation is the most commonly used method for GV preparation. However, the electroformation of GVs is hindered in highly concentrated ionic solutions, limiting their application as cell models for research under physiological conditions. In this study, giant multilayer vesicles were successfully generated in physiological saline using a modified electroformation device by adding an insulating layer between the two electrode plates. The influence of the electric frequency and strength on the electroformation of GVs in physiological saline was explored, and a possible mechanism for this improvement was assessed. It has been shown that an insulating layer between the two electrodes can improve the electroformation of GVs in physiological saline by increasing the electrical impedance, which is weakened by the saline solution, thereby restoring the reduced effective electric field strength. Furthermore, macromolecular plasmid DNA (pDNA) was successfully encapsulated in the electroformed GVs of the modified device. This modified electroformation method may be useful for generating eukaryotic cell models under physiological conditions.

Highly Thermally Conductive Triple-Level Ordered CNT/PVA Nanofibrous Films.

The escalating thermal power density in electronic devices necessitates advanced thermal management technologies. Polymer-based materials, prized for their electrical insulation, flexibility, light weight, and strength, are extensively used in this field. However, the inherent low thermal conductivity of polymers requires enhancement for effective heat dissipation. This work proposes a novel paradigm, emphasizing ordered structures with functional units, to create triple-level, ordered, low-filler loading of multi-walled carbon nanotube (MWCNT)/poly(vinyl alcohol)(PVA) nanofibrous films. By addressing interfacial thermal resistance through -OH groups, the coupling between polymer and MWCNT is strengthened. The triple-level ordered structure comprises aligned PVA chains, aligned MWCNTs, and aligned MWCNT/PVA composite fibers. Focusing on the filler's impact on thermal conductivity and chain orientation, the thermal transport mechanisms have been elucidated level by level. Our MWCNT/PVA composite, with lower filler loadings (10 wt.%), achieves a remarkable TC exceeding 35.4 W/(m·K), surpassing other PVA composites with filler loading below 50 wt.%.

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance

The development of lead-free dielectric capacitors with high recoverable energy storage density and high energy storage efficiency is important for improving the overall performance of electronic and power systems. BaTiO3 (BTO) is one of the most common ferroelectric materials and has attracted much attention for energy storage applications in the past decades due to its excellent dielectric and ferroelectric properties. However, high remnant polarization and low electrical breakdown strength of BTO limit its development in energy storage applications. Many efforts (e.g., elements doping, interface/heterostructure, etc.) have been made to improve the energy storage density of BTO thin films. In this paper, Ba1-xNixTiO3 thin films (x = 0, 0.02, 0.04, 0.06, 0.08; abbreviated as BNxT) were synthesized via sol-gel and spin-coated method. The effect of Ni doping on the structural, dielectric, ferroelectric and energy storage properties of BTO thin films has been studied. The results confirmed that with the increase of Ni doping, a second phase arises and the dielectric constant decreases. While appropriate Ni doping led to the improvement of the breakdown strength, further increase of Ni deteriorated the energy storage because of the high oxygen vacancy. Finally, optimized energy storage performance was obtained for BN0.04T thin film: dielectric constant of 401, dielectric loss of 0.002, recoverable energy density of 20.2 J/cm3 and energy storage efficiency of 83.6% at 965 kV/cm. Meanwhile, the remnant and maximum polarization of the films were 0.06 μC/cm2 and 50 μC/cm2, respectively. BN0.04T thin film has an excellent application prospect and is expected to appear as a component in the future composite energy storage film system.

ДОСЛІДЖЕННЯ ПОДВІЙНИХ ЗАМКНЕНЬ НА ЗЕМЛЮ В МЕРЕЖАХ 10 КВ З ІЗОЛЬОВАНОЮ НЕЙТРАЛЛЮ

Reliability indicators of power supply systems as a whole are largely determined by the level of reliability of distribution electrical networks with a voltage of 6-35 kV. Emergency in networks with a voltage of 6-35 kV, operating in the mode with an isolated neutral, is often associated with internal overvoltages. Single-phase short-circuits occur in places of defects in the insulation of cable lines and substation equipment due to the aging of the insulation, non-compliance with the manufacturing technology of insulating structures at factories, non-compliance with the requirements of the instructions during the installation and operation of the equipment, as well as due to mechanical damage, which, sometimes at the time of their appearance, lead to only a partial decrease in electrical strength. Overloads lead to defects. Single-phase short-circuits in 10 kV networks that are not eliminated in time can lead to double earth faults. For protection in these networks, such protections as current cut-off, maximum current protection, current cut-off, zero-sequence current protection, current protections with blocking at minimum voltage are used. However, there are cases when there are cases of negative operation of such protections at a 10 kV substation during double earth faults. For example, a phase A short circuit occurred on the first line, which receives power from the buses of the investigated substation, and another short circuit (phase B) occurred on the second line. Instead of tripping the two damaged lines, the input circuit breaker tripped by mistake. This de-energized other (undamaged) lines that are fed from the same bus section as the damaged lines. Under such conditions, further studies of the currents in the lines during double circuits are required. For this, the use of the Matlab application program package is justified. This will significantly reduce the costs of physical modeling and verification of proposed proposals. The paper presents the results of studies of double earth faults in 10 kV networks with an isolated neutral in the "MATLAB" program package.

Nano-Titanium Dioxide Filler Particles in Soybean Methyl Ester for an Improvement of Electrical Breakdown Strength of Soybean Vegetable Oil as a Transformer Oil Substitute

Power transformers use mineral oil as an insulating liquid due to its excellent dielectric properties. However, mineral oil is a non-renewable resource and is toxic to the environment when leaked. The purpose of this research is to examine vegetable oil containing nanotitanium dioxide as a substitute for mineral transformer oil. Vegetable insulating oils are environmentally benign and have good breakdown voltage (BV) and high ignition points that can decompose naturally in the event of a leak. Nevertheless, the high viscosity of vegetable oil slows down the flow rate in the transformer cooling. To overcome this problem, the process of transesterification was used to produce soybean methyl ester (SBME). SBME is used as an insulating liquid including composite filler of titanium dioxide (TiO2) nanoparticles. Electrical breakdown voltage (BV) tests were performed following ASTM D1816 standards. Results demonstrated that SBME has a greater BV than natural soybean oil. Also, the addition TiO2 nanoparticles increases the BV of the SBME’s mixture. All cases of nanoparticle methyl ester (NPME) conducted in the experiments exhibited a BV higher than 28 kV which is well above the standard value.

Development of method for frequency regulation of output current in high-voltage transformerless resonant chargers of capacitive energy storage devices

The object of research is high-voltage systems of electric discharge installations for various technological purposes. The work reports solving the problem of enabling the rate of charging of a capacitive energy storage, set by the requirements of a certain high-voltage technology. The quantitative characteristics of the deviation of the output current of the resonant inverter from the set stabilized value when changing the switching frequency of inverter switches in the range of output voltage change from 0 to 20 kV were determined. Using the Fourier transform of the rectangular input voltage, the frequency regulation possibility of the output current of the charger for capacitive energy storage devices was analyzed. Estimation dependences of the output current of resonant inverter on the load resistance and frequency deviation from resonant frequency were derived. These dependences could be used to implement frequency control over the switching inverter transistors, with the help of which the given effective value of the output current of the resonant inverter is obtained. A method of frequency regulation of the output current in high-voltage transformerless resonant charging devices of capacitive energy storage devices has been developed. Special feature of this method is that it is based on the frequency dependence of reactive resistances of the inductance and capacitance of the resonant circuit connected in series. Owing to that, it makes it possible to adjust the switching frequency of the inverter’s power switches depending on the relative resistance of the load and the specified growth rate of the capacitive energy storage voltage. The results reported here could be used in the design of benches for testing the electrical strength of high-voltage cables, as well as for the construction of high-voltage transformerless chargers in systems of electric discharge impulse processing of materials

High energy storage performance of lead‐free Nb‐modified (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)TiO3 high‐entropy ceramics

AbstractOwing to the intrinsic chemical disorder of microscopic composition, perovskite high‐entropy ceramics exhibit dielectric relaxation behaviors and are favorable for energy storage performance. In this work, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(Ti1−xNbx)O3 (BNCBST‐xNb, 0.01 ≤ x ≤ 0.25) ceramics were prepared using a hydrothermal method. The results indicate that Nb doping into BNCBST induces lattice expansion and deepens dielectric relaxation. Moreover, the BNCBST‐xNb ceramics exhibit a great enhancement of electrical breakdown strength (Eb) with Nb content, which results from the reduction of grain size, the increase of resistivity, the decrease of oxygen vacancies, and the enlargement of band gap width. Consequently, the BNCBST‐0.15Nb system presents an outstanding Eb of 497 kV/cm with excellent recoverable energy density (Wrec = 3.85 J/cm3) and efficiency (η = 87.7%), accompanying by the wide temperature stability (Wrec and η vary within ± 9.8% and ± 1.4% at 40–100°C) and fast discharge rate (t0.9 = 88 ns). The significant improvement of Eb and energy storage properties suggest that our research offers an effective strategy for developing lead‐free energy storage ceramics.