Current Breakdown Research Articles

Direct, spatially resolved observation of defect states with electromigration and degradation of single crystal SrTiO3

Laterally and depth-resolved cathodoluminescence spectroscopy (DRCLS) provided direct, nanoscale measurements of oxygen vacancy and oxygen vacancy complex distributions in undoped and Fe-doped SrTiO3 with high temperature electric field stress associated with dielectric resistance degradation. DRCLS provided direct and spatially resolved observation of oxygen vacancy migration driven by external electric fields from the anode to the cathode in undoped SrTiO3 between laterally separated electrodes, resulting in increased current leakage and lower thermal breakdown strength. DRCLS measurements through planar Pt electrodes after high temperature electric field cycling reveal pronounced oxygen vacancy depletion within the surface space region of the Pt/SrTiO3 Schottky barrier as predicted theoretically. These results provide a direct insight into the transient states impacting the conduction during the electromigration of the oxygen vacancies. The deconvolution of different peaks and their intensity variations relative to the direct bandgap provide methods to gauge the relative defect energetics of these gap states. These data are discussed in relation to providing a tool to further understand conduction in mixed ionic conductors.

Coupling Effect of Molecular Chain Displacement and Carrier Trap Characteristics on DC Breakdown of HDPE/LDPE Blend Insulation.

This work focuses on the coupling effect of molecular chain displacement and trap characteristics on direct current (DC) breakdown properties of high density/low density polyethylene (HDPE/LDPE) blend insulation. Frequency domain spectroscopy (FDS) and isothermal discharge current (IDC) are used to characterize the dielectric relaxation and trap characteristics of HDPE/LDPE blends. A DC breakdown model is proposed to reveal the mechanisms of the molecular chain displacement and carrier trap on the DC breakdown strength. The dielectric relaxation α and δ present segmental motions and thermal ion polarization behaviours of HDPE/LDPE blends, respectively. α dielectric relaxation strength (Δεα) increases as the amount of HDPE increases from 0 to 5 wt%, and then declines with a further increase of HDPE content to 20 wt%. According to the velocity equation, the increase of Δεα will increase the molecular chain displacement, resulting in a larger free volume, which will provide electrons with larger free path λ to form hot electrons. A positive correlation exists between the activation energy of the dielectric relaxation process δ and trap density, and the increase of δ dielectric relaxation strength (Δεδ) will adversely affect the breakdown strength of the specimen. HDPE/LDPE blends with 15 wt% HDPE content have lower Δεα and lowest Δεδ, which decreases the mean free path λ of molecular chain and thermal ion polarization. At the same time, it has the highest deep trap density, thus increasing the probability of hot electrons being captured and improving the DC breakdown strength. It is concluded the breakdown of the dielectric is synergistically affected by the molecular chain displacement and carrier trap.

GeSn/GeSiSn double-heterojunction short channel tunnel field-effect transistor design

The traditional GeSn/GeSiSn single-heterojunction (SH) n-channel tunneling field-effect transistor (NTFET) faces a serious off-state current (IOFF) breakdown and a subthreshold swing (SS) degradation when the channel length is scaled to 10 nm. In this work, we propose a double-heterojunction (DH) short channel NTFET by utilizing heterojunction engineering. A 60% lower IOFF value (4.83 × 10−10 A μm−1), a 6.2 times higher ION value (9.39 × 10−6 A μm−1) and an SS of 39.14 mV/dec are achieved in the DH NTFET at 0.3 V compared to the SH NTFET when the channel length is 10 nm.

UV-Initiated Crosslinking Reaction Mechanism and Electrical Breakdown Performance of Crosslinked Polyethylene.

The ultraviolet (UV) irradiation crosslinking reactions of polyethylene and the electronic properties of photo-initiators and reaction products are theoretically investigated by the first-principles calculations. The crosslinked polyethylene (XLPE) materials are prepared in experiments that employ the UV-initiated crosslinking technique with different photon-initiation systems. Infrared spectrum and the alternating current dielectric breakdown strength of UV-initiated XLPE are tested to explore the effect of reaction products on the breakdown characteristics in combination with the electron structure calculations. The theoretical calculations indicate that the 4-hydroxybenzophenone laurate, which is compatible with polyethylene, can effectively initiate crosslinking reactions of polyethylene molecules under UV photon excitation and will produce reaction by-products from carbonyl radicals; as a macromolecular auxiliary crosslinker, the monomer or homopolymer of dioleyl-2,2′,4,4′-tetraallyl isocyanurate can form chemical connections with multiple polyethylene molecules acting as a crosslinking node in a photon-initiated reaction process. The carbonyl, hydroxyl, or ester groups of reaction by-products are capable of capturing hot electrons to prevent polyethylene molecules from impact ionization, and thus will increase the breakdown electric field. The macromolecular auxiliary crosslinker and the macromolecular photon initiator as well as its reaction by-product can convert the energy of their captured high-energy electrons into heat, which can act as a voltage stabilizer. The molecule characterization of infrared spectra demonstrates that the characteristic absorption peaks of the carbonyl in the macromolecular photon initiator and the allyl in the macromolecular auxiliary crosslinking agent are gradually decreasing in intensity as the crosslinking reaction proceeds, which is consistent with the conclusion from theoretical calculations. Compared with the small molecular photon-initiation system generally used in the photon-initiated crosslinking process, the higher dielectric breakdown field of XLPE being prepared by utilizing a macromolecular photon-initiation system is in good agreement with the calculation results of electronic affinity and ionization potential. The consistent results of the experiments and first-principles calculations elucidate the fundamental mechanism of the UV-initiation crosslinking technique and suggest a prospective routine to improve the insulation strength for developing high-voltage XLPE insulating materials.

Enhanced Electrical Properties of Polyethylene-Graft-Polystyrene/LDPE Composites.

Nanocomposite dielectrics show a great potential application in high voltage direct current cables for their obvious improvements in electrical properties. In the present manuscript, nanocomposite composed of low-density polyethylene and nanoscale polystyrene particles is studied by using low-density polyethylene grafted with polystyrene molecule. Fourier-transform infrared spectra reveal successful grafting of the polystyrene molecule onto the low-density polyethylene chain and the scanning electron microscope image shows the homogeneously dispersed nanoscale polystyrene particles. The presence of the polystyrene nanoparticles obviously improves the dielectric properties, such as the direct current breakdown strength and space charge inhibition. The conductivity and thermally stimulated current characteristics imply the deep traps in the composite increase obviously. Density functional theory calculation reveals that the grafted polystyrene can accommodate both shallow and deep electron carriers, and the depth of the hole traps are as deep as 2.07 eV.

Повышение пропускной способности ограничителей перенапряжений в составе вакуумных выключателей постоянного тока

One of the problems that must be solved when short-circuit currents breakdown in a DC vacuum circuit breaker is the dissipation of electromagnetic energy stored in the inductance of the Lc network and brought by the source at the time of the current breakdown, as well as limiting the overvoltages on the circuit breaker elements. The high level of overvoltages U»Lсdi/dt is due to the rapid fall of the di/dt trip current in the network with inductance Lc, which, for example, in traction networks of electrified rail transport reaches 15 mH. To solve this problem, a nonlinear overvoltage arrestors (NOA) is used, which is installed parallel to the circuit breaker and provides for the overvoltage limiting and also serves to absorb electromagnetic energy stored in the inductance of the network. The amount of absorbed energy should not exceed the amount of energy dissipated into the outer space. Otherwise, there will be a constant increase in the temperature of the arrester and its subsequent thermal destruction. The energy absorbed in the arrester unit when the current is breakdown (Ibr2Lc/2) depends on the breakdown current Ibr and the inductance of the network Lc. The energy dissipated depends on the design of the arrester unit and the mass of the supply tires. The balance between absorbed and dissipated energy determines the throughput of the arrester unit without degrading it. The throughput of surge arresters with high current pulses is determined by its ability to withstand the max supply tires. The balance between absorbed and dissipated energy determines the throughput of the arrester unit without degrading it. The throughput of surge arresters with high current pulses is determined by its ability to withstand the maximum value of current pulses with duration of several milliseconds. This paper presents the results of numerical simulation and experimental research of ways to increase the throughput of an oxide-zinc (ZnO) surge arrester as part of a DC vacuum circuit breaker.

A short-time physics problem in superconductivity: Stability against quench

This paper investigates the stability problem of superconductors against quench. Numerical Finite Element simulations are applied to calculate the distribution of transient temperature, critical current density and transport current in the conductor cross-section under a disturbance, here flux flow losses. Contrary to standard stability models, the focus of the paper is on situations very close to the superconducting/normal conducting phase transition. The obtained results demonstrate it is not realistic, even in thin films, to assume uniform conductor temperature under a disturbance. A method is suggested on how to predict the time and position of a quench when it is expected to occur in the conductor cross-section. Quench starts locally. Application of a microscopic stability model allows to describe continuous, not abrupt but very fast break-down of transport current in situations close to the phase transition.

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.

Simulation study of direct current vacuum breakdown and its application to high-gradient accelerating structures

It is well known that radio frequency breakdown is one of the main limitations in high frequency accelerators. Similarities have been detected between breakdowns in direct current vacuum gaps and those in superconducting radio frequency cavities. Therefore, cavity break- downs due to electric field phenomena can be understood by studying direct current vacuum breakdowns. Significant irregularity of a surface and a variety of involved processes objectively stipulate a number of factors which may lead to a breakdown. In this paper, the effects of surface conditions, accelerator gradient, pulse length, and operating frequency on the breakdown have been studied by using COMSOL simulation package. It was found that the dependence of breakdown rate on accelerating gradient and pulse length follows scaling laws. Based on the time evolutions of electron density and the potential in cone-cylinder electrode configuration at the pressure of 0.1 Pa, the time scale of a vacuum breakdown has been established. It was also confirmed that the emission from an electrode surface can be regarded as a major factor leading to electrical breakdown in vacuum. The obtained results could be very useful in high-gradient accelerating structures.

Experimental study on gliding discharge mode of rotating gliding arc discharge plasma

Alternating current rotating gliding arc discharge can produce large-scale, wide-range non-equilibrium plasma at atmospheric pressure. In order to investigate the gliding discharge mode, discharge characteristics and Spectral characteristics of AC rotating gliding arc discharge plasma, high speed camera, oscilloscope and spectrometer are used to collect discharge images and electrical signals of rotating gliding arc synchronously. Thus the dynamic behavior of arc and the characteristics of electric signal in the process of rotating gliding arc can be analyzed. The experimental results show that there are two different discharge modes in the rotating gliding arc discharge process, namely the breakdown gliding discharge mode (B-G mode) and the stable gliding discharge mode (A-G mode). The B-G mode is mainly characterized by high-frequency breakdown phenomenon (breakdown-extinguish-breakdown) during the arc gliding process, while the A-G mode is mainly characterized by stable continuous arc sliding. The paper also discusses the working mechanism in which the working parameters influence the gliding arc discharge characteristics. It is shown that the discharge mode and discharge characteristics of arc are the result of the combined action of excitation voltage and gas flow. When the gas flow is large and the excitation voltage is small, the gliding arc is an unstable discharge dominated by the B-G mode. Conversely, when the excitation voltage is large and the gas flow is small, the gliding arc is a stable gliding discharge dominated by the A-G mode. In addition, in B-G mode, the energy consumption is mainly concentrated in the breakdown moment, and the energy release is mainly pulsed. However, when the gliding arc discharge is in A-G mode, the energy dissipation is mainly used to maintain the continuous existence of the arc without extinguishing, and the energy release is stable and continuous. Affected by the gas flow rate and excitation voltage, the breakdown frequency of the B-G mode is greater than that of the A-G mode. Higher repeat breakdown frequency can cause multiple ionization in the process of gliding arc discharge, which produces more active particles. The research conclusions in this paper provide theoretical support for regulating the operating characteristics of the gliding arc discharge. In engineering application, the discharge mode, breakdown frequency and breakdown current of the gliding arc can be adjusted by changing the working parameters to obtain plasma sources with different characteristics.

ESD Improvements on Power N-Channel LDMOS Devices by the Composite Structure of Super Junctions Integrated With SCRs in the Drain Side

This paper studies a composite power n-channel lateral-diffused MOSFET device with a super junction (SJ) and parasitic silicon-controlled rectifier structure (nLDMOS-SJ-SCR) in the drain side, which can be used for electrostatic discharge (ESD) and latch-up (LU) reliability enhancements of 60-V power electronics. For ESD and LU protection considerations, the drain side with an SJ structure integrated with p-n-p- and n-p-n-arranged types of nLDMOS-SCR transistors is demonstrated. According to the experimental data, the layout of the SJ structure in the drain side has positive effects on ESD and LU capabilities. The layout type of nLDMOS-SJ with a pillar width W = 9μm has the highest secondary breakdown current (I t2 ) values; the ESD (LU) improvement was 46.3% (13.3%) compared with the nLDMOS reference sample. Meanwhile, an nLDMOS-SJ with a pillar width W = 27μm has the highest figure of merit (FOM) value. By contrast, an embedded p-n-p-(n-p-n-)arranged type SCR structure was added into the drain side once again. Initially, it has a positive (negative) effect on the ESD reliability. Furthermore, the ESD (figure of merit; FOM) improvement was 37.9% (13.72%) of the corresponding nLDMOS-SJ device for nLDMOS-SJ-SCR (p-n-p) with W = 27μm. Overall, an nLDMOS-SJ device integrated with the p-n-p-arranged-type SCR in the drain side is a favorable choice for ESD and LU improvements.

Dielectric property and energy-storage performance of (1–x)PbTiO3–xBi(Mg0.5Zr0.5)O3 relaxor ferroelectric thin films

Relaxor ferroelectric materials stand out in pulse power devices for their excellent energy-storage performance. Here, Bi(Mg0.5Zr0.5)O3 (BMZ)-modified PbTiO3 (PT) relaxor ferroelectric thin films were prepared on LaNiO3(LNO)(100)/Pt(111)/TiO2/SiO2/Si substrates. (1–x)PbTiO3–xBi(Mg0.5Ti0.5)O3 thin films possess prominent increasing relaxor behavior with increasing of BMZ content, which is conducive to obtaining large polarization difference (Pmax − Pr). Meanwhile, Mg2+ and Zr4+ are beneficial to reduce leakage current density and increase breakdown field strength (BDS). Therefore, 0.6PT–0.4BMZ thin films simultaneously exhibit a high recoverable energy-storage density (Wrec) of 32.3 J/cm3 and a large energy-storage efficiency (η) of 51.4%. In addition, 0.6PT–0.4BMZ film shows favorable frequency (100 Hz–5 kHz) and temperature (25–130 °C) stability in energy-storage density, and change rate of both is below 5% within measurement range. This work highlights (1 − x)PT − xBMZ composites as promising materials in energy-storage fields.

Temperature Effects on the Dielectric Properties and Breakdown Performance of h-BN/Epoxy Composites.

Epoxy–boron nitride composites are promising insulating materials, and it is highly important to understand their insulating performances at different temperatures with different nano-doping amounts. In this study, we investigated the effects of different mass fractions of epoxy–micron hexagonal boron nitride composites on their thermal conductivity, as well as the effects of temperature and mass fraction on their insulating performances. The results demonstrated that the thermal conductivity of epoxy–micron hexagonal boron nitride composites was superior to that of neat epoxy. The thermal conductivity of epoxy–micron hexagonal boron nitride composites increased with the mass fraction of hexagonal boron nitride, and their dielectric constant and dielectric loss increased with temperature. The dielectric constant of epoxy–micron hexagonal boron nitride composites decreased as the mass fraction of hexagonal boron nitride increased, while their dielectric losses decreased and then increased as the mass fraction of hexagonal boron nitride increased. Due to internal heat accumulation, the alternating current breakdown strength of epoxy–micron hexagonal boron nitride composites increased and then decreased as the mass fraction of hexagonal boron nitride increased. Additionally, as the temperature increased, the composites transitioned from the glassy state to the rubbery or viscous state, and the breakdown strength significantly degraded.

Electrostatic-Discharge-Immunity Impacts in 300 V nLDMOS by Comprehensive Drift-Region Engineering

Electrostatic discharge (ESD) events are the main factors impacting the reliability of Integrated circuits (ICs); therefore, the ESD immunity level of these ICs is an important index. This paper focuses on comprehensive drift-region engineering for ultra-high-voltage (UHV) circular n-channel lateral diffusion metal-oxide-semiconductor transistor (nLDMOS) devices used to investigate impacts on ESD ability. Under the condition of fixed layout area, there are four kinds of modulation in the drift region. First, by floating a polysilicon stripe above the drift region, the breakdown voltage and secondary breakdown current of this modulation can be increased. Second, adjusting the width of the field-oxide layer in the drift region when the width of the field-oxide layer is 5.8 μm will result in the minimum breakdown voltage (105 V) but the best secondary breakdown current (6.84 A). Third, by adjusting the discrete unit cell and its spacing, the corresponding improved trigger voltage, holding voltage, and secondary breakdown current can be obtained. According to the experimental results, the holding voltage of all devices under test (DUTs) is greater than that of the reference group, so the discrete HV N-Well (HVNW) layer can effectively improve its latch-up immunity. Finally, by embedding different P-Well lengths, the findings suggest that when the embedded P-Well length is 9 μm, it will have the highest ESD ability and latch-up immunity.

Quantitative evaluation of the breakdown process of spark discharge for spark-ignition engines

For spark-ignition (SI) engines, downsizing, exhaust gas recirculation and lean burn are promising methods for meeting more stringent emission regulations and lower fuel consumption requirements. With these technologies, high density and high flow velocity around the spark plug at spark timing bring severe challenges for stable ignition. The ignition processes could be affected by breakdown phases and restrikes under high-density conditions. A quantitative evaluation for the breakdown phase is of great significance especially for high power density engines. In this study, the experiments with pressure up to 40 bar and temperature up to 450 K are established to evaluate the breakdown voltage and current, with different spark plug gaps. The breakdown voltage is related to the ambient density, spark plug gap distance and gas composition. The coil parameters have little effects on the breakdown voltage. The breakdown current shows positive correlation with the breakdown voltage, and is also affected by the coil characteristics. The breakdown voltage and current show the nonlinear correlations with the pressure and gap distance. With the increase of pressure or gap distance, the increase rates of the breakdown voltage and current decrease. The fuel concentration and species have little effects on the breakdown voltage when the fuel concentration is applicable for engine operations. Finally, a novel expression of the breakdown voltage is constructed as a function of ambient pressure, temperature and spark plug gap distance. The newly developed expression is valuable for simulating spark ignition processes for a wide range of ambient density for SI engines.

Improvement of an Experimental Routine for Electrochemical Composition Measurements of SmCl3 in LiCl-KCl Eutectic Salt Systems

Cyclic voltammetry (CV) was used to study SmCl3 at concentrations of 0.42 to 8.99 wt% in molten eutectic LiCl-KCl (44.2:55.8 wt%) at 773 K. For each sample, CV was repeated at different electrode surface areas to measure the peak current density. By analyzing the measured peak current density and concentration relationship with the Randles-Sevcik equation, the Sm(III) diffusivity for each sample was calculated. These diffusion coefficients ranged from 0.934 × 10−5 to 1.572 × 10−5 cm2‧s−1, showing no noticeable trend with a change in concentration. The samples were then divided into two groups of five. The first group was used to develop a calibration model for concentration prediction, while the second group was used to test and validate the model. The first model was based on the relationship between current density and concentration. This model had a very low limit of detection of 0.14 wt% and very low error as evaluated by the root-mean-square error of calibration of 0.108 wt%. The second model was a multivariate approach utilizing the current density values and laser-induced breakdown spectroscopy (LIBS) intensities as regressors; however, the introduction of LIBS data showed an increase in the model’s prediction error when compared to the first model. The electrode withdrawal method proved to be a preferable option due to a substantial increase in precision.

Conditional Capacity and Transmit Signal Design for SWIPT Systems With Multiple Nonlinear Energy Harvesting Receivers

In this paper, we study information-theoretic limits for simultaneous wireless information and power transfer (SWIPT) systems employing practical nonlinear radio frequency (RF) energy harvesting (EH) receivers (Rxs). In particular, we consider a SWIPT system with one transmitter that broadcasts a common signal to an information decoding (ID) Rx and multiple EH Rxs. Owing to the nonlinearity of the EH Rxs’ circuitry, the efficiency of wireless power transfer depends on the waveform of the transmitted signal. We aim to answer the following fundamental question: What is the optimal input distribution of the transmit signal waveform that maximizes the information transfer rate at the ID Rx conditioned on individual minimum required direct-current (DC) powers to be harvested at the EH Rxs? Specifically, we study the conditional capacity problem of a SWIPT system impaired by additive white Gaussian noise subject to average-power (AP) and peak-power (PP) constraints at the transmitter and nonlinear EH constraints at the EH Rxs. To this end, we develop a novel nonlinear EH model that captures the saturation of the harvested DC power by taking into account not only the forward current of the rectifying diode but also the reverse breakdown current. Then, we derive a novel semi-closed-form expression for the harvested DC power, which simplifies to closed form for low input RF powers. The derived analytical expressions are shown to closely match circuit simulation results. We solve the conditional capacity problem for real- and complex-valued signalling and prove that the optimal input distribution that maximizes the rate-energy (R-E) region is unique and discrete with a finite number of mass points. Furthermore, we show that, for the considered nonlinear EH model and a given AP constraint, the boundary of the R-E region saturates for high PP constraints due to the saturation of the harvested DC power for high input RF powers. In addition, we devise a suboptimal input distribution whose R-E tradeoff performance is close to optimal. All theoretical findings are verified by numerical evaluations.

Measurements of Magnetic Pulse Bursts During Initial Continuous Current of Negative Rocket‐Triggered Lightning

AbstractDuring the SHandong Triggering Lightning Experiment (SHATLE) in summer of 2014 and 2015 and the Guangdong Comprehensive Observation Experiment on Lightning Discharge (GCOELD) campaign in 2018, we have conducted the observations of the magnetic pulse bursts (MPBs) during the initial continuous current in negative rocket‐triggered lightning. The MPBs are commonly recorded at the main site of SHATLE (970 m from the rocket launch site), but the synchronous magnetic field (B‐field) measurements at the close site of SHATLE (78 m from the rocket launch site) show the slow variations with small MPBs superposing on them. Note that both the charge transfer and the relative brightness increase notably during the appearance of the MPBs. After shifting up the operation frequency of the magnetic sensor, the MPBs can be observed at close distance (80 m from the rocket launch site) obviously in GCOELD. Observations show that the radiation sources of MPBs originate from the breakdown in the vicinity of the leader tip, but the sources of the initial magnetic pulses (IMPs) measured at the very initial stage of triggered lightning are from the radiation of the whole steel wire. The continuous current measured at the channel base during the MPBs cannot reflect the characteristics of breakdown current, because the current is attenuated and dispersed when propagating along the high‐impedance leader channel. The average peak current associated with the MPBs is estimated to be on the order of kiloamperes.

Molybdenum Oxides Coatings for High Demanding Accelerator Components

Large electric gradients are required for a variety of new applications, notably including the extreme high brightness electron sources for X-ray free electron lasers (FELs), radio-frequency (RF) photo-injectors, industrial and medical accelerators, and linear accelerators for particle physics colliders. In the framework of the INFN-LNF, SLAC (USA), KEK (Japan), UCLA (Los Angeles) collaboration, the Frascati National Laboratories (LNF) are involved in the modelling, development, and testing of RF structures devoted to particles acceleration by high gradient electric fields of particles through metal devices. In order to improve the maximum sustainable gradients in normal-conducting RF-accelerating structures, both the RF breakdown and dark current should be minimized. To this purpose, studying new materials as well as manufacturing techniques are mandatory to identify better solutions to such extremely requested applications. In this contribution, we discuss the possibility of using a dedicated coating on a solid copper sample (and other metals) with a relatively thick film to improve and optimize breakdown performances and to minimize the dark current. We present here the first characterization of MoO3 films deposited on copper by pulsed-laser deposition (PLD).

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.