Dielectric Breakdown Electric Field Research Articles

Enhanced energy storage performance in NBT-based MLCCs via cooperative optimization of polarization and grain alignment

Dielectric ceramics possess a unique competitive advantage in electronic systems due to their high-power density and excellent reliability. Na1/2Bi1/2TiO3-based ceramics, one type of extensively studied energy storage dielectric, however, often experience A-site element volatilization and Ti4+ reduction during high-temperature sintering. These issues may result in increased energy loss, reduced polarization and low dielectric breakdown electric field, ultimately making it challenging to achieve both high energy storage density and efficiency. To address these issues, we introduce a synergistic optimization strategy that combine polarization engineering and grain alignment engineering. First principles calculations and experimental analyses show that the doping of Mn2+ can suppress the reduction of Ti4+ in Na1/2Bi1/2TiO3-based ceramics and enhance ion off-centering displacements, thereby reducing energy loss and improving polarization. In addition, we prepared multilayer ceramic capacitors with grains oriented along the <111> direction using the template grain growth method. This approach effectively reduces electric-field-induced strain by 37% and markedly enhances breakdown electric field by 42% when compared with nontextured counterpart. As a result of this comprehensive strategy, <111 >-textured Na1/2Bi1/2TiO3-based multilayer ceramic capacitors achieve an ultra-high energy density of 15.7 J·cm−3 and an excellent efficiency beyond 95% at 850 kV·cm−1, exhibiting a superior overall energy storage performance.

PMSNet: Multiscale Partial-Discharge Signal Feature Recognition Model via a Spatial Interaction Attention Mechanism.

Partial discharge (PD) is a localized discharge phenomenon in the insulator of electrical equipment resulting from the electric field strength exceeding the local dielectric breakdown electric field. Partial-discharge signal identification is an important means of assessing the insulation status of electrical equipment and critical to the safe operation of electrical equipment. The identification effect of traditional methods is not ideal because the PD signal collected is subject to strong noise interference. To overcome noise interference, quickly and accurately identify PD signals, and eliminate potential safety hazards, this study proposes a PD signal identification method based on multiscale feature fusion. The method improves identification efficiency through the multiscale feature fusion and feature aggregation of phase-resolved partial-discharge (PRPD) diagrams by using PMSNet. The whole network consists of three parts: a CNN backbone composed of a multiscale feature fusion pyramid, a down-sampling feature enhancement (DSFB) module for each layer of the pyramid to acquire features from different layers, a Transformer encoder module dominated by a spatial interaction-attention mechanism to enhance subspace feature interactions, a final categorized feature recognition method for the PRPD maps and a final classification feature generation module (F-Collect). PMSNet improves recognition accuracy by 10% compared with traditional high-frequency current detection methods and current pulse detection methods. On the PRPD dataset, the validation accuracy of PMSNet is above 80%, the validation loss is about 0.3%, and the training accuracy exceeds 85%. Experimental results show that the use of PMSNet can greatly improve the recognition accuracy and robustness of PD signals and has good practicality and application prospects.

Bi0.5Na0.5TiO3-based energy storage ceramics with excellent comprehensive performance by constructing dynamic nanoscale domains and high intrinsic breakdown strength

Lead-free ceramic-based dielectric capacitors show huge potential in electrical energy storage in pulsed power systems due to their fast charge/discharge rate, ultrahigh power density and environmental friendliness. However, unsatisfied charge/discharge performance characterized by inferior recoverable energy storage density (Wrec generally <5 J/cm3) has become a key bottleneck to restrict their applications in cutting-edge energy storage devices. In this paper, we focus on simultaneously realizing ultrahigh Wrec and efficiency (ƞ) in eco-friendly Bi0.5Na0.5TiO3 (BNT)-based dielectric ceramics via chemical doping. Interestingly, highly dynamic polar nanoregions (PNRs) and nanodomains are constructed by incorporating Sr0.7Nd0.2TiO3 (SNT) into 0.94BNT-0.06BaTiO3. Of great importance, the resulting relaxor ferroelectrics (RFEs) exhibit high bulk resistivity, submicron grain size and wide band gap due to high level of SNT doping accompanying with 1 at% Nb donor doping. Therefore, excellent energy storage properties with ultrahigh Wrec∼8.08 J/cm3 and ƞ∼92.1% are achieved due to coexistence of large polarization difference (ΔP=Pmax−Pr) and giant dielectric breakdown electric field (Eb∼540 kV/cm). Furthermore, excellent temperature/frequency/cycling stability characterized by ΔWrec < ±4% and Δη < ±2% ensure the energy storage applications of the studied dielectric ceramics over an enormous range of scales.

Measurement of Breakdown Electric Field Strength for Vegetation and Hydrocarbon Flames

A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.

Large energy storage efficiency of the dielectric layer of graphene nanocapacitors

Electric capacitors are commonly used in electronic circuits for the short-term storage of small amounts of energy. It is desirable however to use capacitors to store much larger energy amounts to replace rechargeable batteries. Unfortunately existing capacitors cannot store sufficient energy to be able to replace common electrochemical energy storage systems. Here we examine the energy storage capabilities of graphene nanocapacitors, which are tri-layer devices involving an Al film, Al2O3 dielectric layer, and a single layer of carbon atoms, i.e., graphene. This is a purely electronic capacitor and therefore it can function in a wide temperature interval. The capacitor shows a high dielectric breakdown electric field strength, of the order of 1000 kV mm−1 (i.e., 1 GV m−1), which is much larger than the table value of the Al2O3 dielectric strength. The corresponding energy density is 10–100 times larger than the energy density of a common electrolytic capacitor. Moreover, we discover that the amount of charge stored in the dielectric layer can be equal or can even exceed the amount of charge stored on the capacitor plates. The dielectric discharge current follows a power-law time dependence. We suggest a model to explain this behavior.

Enhanced interfacial and electrical characteristics of 4H-SiC MOS capacitor with lanthanum silicate passivation interlayer

The detrimental sub-oxide (SiOx) interfacial layer formed during the 4H-SiC metal-oxide-semiconductor (MOS) capacitor fabrication will drastically damage its device performance. In this work, an ultrathin lanthanum silicate (LaSiOx) passivation layer was introduced to enhance the interfacial and electrical characteristics of 4H-SiC MOS capacitor with Al2O3 gate dielectric. The interfacial LaSiOx formation was investigated by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The 4H-SiC MOS capacitor with ultrathin LaSiOx passivation interlayer shows excellent interfacial and electrical characteristics, including lower leakage current density, higher dielectric breakdown electric field, smaller C–V hysteresis, and lower interface states density and border traps density. The involved mechanism implies that the LaSiOx passivation interlayer can effectively restrain SiOx formation and improve the Al2O3/4H-SiC interface quality. This technique provides an efficient path to improve dielectrics/4H-SiC interfaces for future high-power device applications.

Preparation of Al2O3 film by sol–gel method on thermally evaporated Al film

Sol–gel spin-coated Al2O3 film was deposited on quartz glass substrate with thermally evaporated Al film. Optical micrographs show that the Al film break forming perforated pinholes after the Al2O3 film was thermally processed. Pinholes on the film can be reduced by inserting a metal transition layer between the quartz glass substrate and the Al film but cannot be avoided after thermal process. Doping of scandium in evaporation aluminum cannot perfectly prevent the Al films from breaking and perforation. The breaking and perforation during the fabrication of the Al2O3 film can be dramatically reduced by heating the quartz glass substrate at 320 °C during thermal evaporation. The J–E curves show that the bottom Al electrode greatly affected the dielectric breakdown electric field.

Modification of Deposition Process of Piezoelectric Polycrystalline Film by Hydrothermal Method -Improvement of the Deposition Process by Pre-Treatment Using Hydrogen Peroxide

AbstractWe have studied on hydro-thermally synthesis of Pb(Ti, Zr)O3(PZT)piezoelectric polycrystalline thick film on titanium (Ti) substrate. The purpose of this study is resolving the problems for application of PZT hydrothermal polycrystalline thick film to the ultra miniature high frequency medical ultrasound array probe. The problems were the existence of pinholes in the deposited PZT film, the rough surface of that, low dielectric breakdown electric field etc. The surface of Ti substrate was pretreated to have hydrophilic property by using high reactivity of hydrogen peroxide for resolving the problems in this study. As results, hydrophilic property on the surface of Ti substrate was improved. Surface of PZT hydrothermal polycrystalline thick film without pinholes and smooth surface of that were obtained. Furthermore, the material properties like density, Young's modulus and piezoelectric constant d31 were increased by the pretreatment of Ti substrate. Consequently, dielectric breakdown electric field of PZT hydrothermal polycrystalline film was improved.

Silicon nitride deposited by inductively coupled plasma using dichlorosilane and ammonia

Silicon nitride films were deposited at low temperature (350°C and pressure of 60 mTorr), on silicon substrates, using an inductively coupled plasma chemical vapour deposition system. Different ammonia to dichlorosilane flow ratios (1.4–9.5) and RF powers (25 and 50 W) were adopted for comparison. Deposition rates of the order of 2.6–12.3 nm min −1 and refractive indexes ranging from 1.710 to 1.818 were determined by ellipsometry. Fourier transformed infrared spectra revealed the presence of SiN breathing and stretching modes, Si–NH–Si bending mode and NH stretching mode. The dielectric constant (4.5–5.8), dielectric breakdown electric field (0.36 MV/mm) and conductivity (3×10 −12 (Ω cm) −1) were determined by capacitance–voltage and current–voltage measurements. The films present low compressive total stress but when increasing the concentration of the nitrogen in the film the total stress tends to become tensile.

Electrical properties of ultrathin oxide grown by high pressure oxidation and N2O nitridation for ULSI device applications

For the first time, the feasibility of ultrathin oxides grown by high pressure oxidation (HIPOX) technology in O2 ambient and nitrided in N2O ambient with rapid thermal processing has been investigated in order for them to be used as a gate oxide of ULSI devices. The dielectric breakdown electric field (E BR) and the midgap interface trap density (D itm) of the nitrided-HIPOX oxide are −13:9MVcm−1 and 2 × 1010cm−2eV−1 respectively which are almost the same as those of the control oxide and the nitrided-control oxide. The time-tobreakdown (tBD) of the nitrided-HIPOX oxide is longer than that of the control oxide at low electric field (<10−4 A cm−2) owing to the combination of nitrogen and defects near the Si−SiO2 interface during nitridation. The lifetimes of the nitrided-HIPOX oxides increase initially, reaching a maximum value of 1:2 × 109 s at a stress current density of 1 × 10−6 A cm−2,corresponding to over 10 years, and then decrease as nitridation proceeds.

Nonuniversal breakdown behavior in superconducting and dielectric composites.

We discuss the critical current density ${J}_{c}$ of composites where a fraction p of the material is superconducting and the dielectric breakdown electric field ${E}_{c}$ of composites where a fraction p of the material is metallic. Both of these nonlinear processes are characterized by power-law behavior near the percolation threshold ${p}_{c}$, ${J}_{c}$\ensuremath{\propto}(p-${p}_{c}$${)}^{v}$ and ${E}_{c}$\ensuremath{\propto}(${p}_{c}$-p${)}^{y}$. The exponents v and y are nonuniversal, depending strongly on both the dimensionality and microstructure of the composite.