Pulsed Power Devices Research Articles

Enhanced energy-storage density in (Pb0.98La0.02)(Zr0.45-xSn0.55Hfx)0.995O3 antiferroelectric ceramics

Antiferroelectric ceramics with unique characteristics of electric-field-induced antiferroelectric to ferroelectric phase transitions and ultra-fast charging-discharging rate, which are demanded in high pulse power devices. In this work, (Pb0.98La0.02)(Zr0.45-xSn0.55Hfx)0.995O3 (PLZSH) antiferroelectric ceramics with x = 0∼0.20 were prepared via a conventional solid-state reaction approach. Incommensurate modulation structure with a 1/n<110> superlattice was observed in AFE at room temperature, which was associated with the unique domain boundaries, contributing the obvious declined AFE-FE phase transition electric field as well as the enhanced energy storage density. It was also observed that the maximum recoverable energy storage density (Wrec) increases from 2.93 J/cm3 (x = 0) to 5.72 J/cm3 (x = 0.15), and the corresponding energy-storage efficiency uprises from 82.4 % to 87.8 % with the increasing x at 280 kV/cm. The superior energy density and efficiency indicate that the obtained PLZSH antiferroelectric ceramics are promising for practical applications in pulse power devices.

Boosting Energy Storage Performance of Glass Ceramics via Modulating Defect Formation During Crystallization.

Along with the demand for further miniaturization of high and pulsed power devices, it becomes more and more important to realize ultrahigh recoverable energy storage density (Wrec ) with high energy storage efficiency (η) and ultrahigh discharge energy storage density (Wd ) accompanied by high power density (Pd ) in dielectrics. To date, it remains, however, a big challenge to achieve high Wrec or Wd in glass ceramics compared to other dielectric energy storage materials. Herein, a strategy of defect formation modulation is applied to form "amorphous-disordered-ordered" microstructure in BaTiO3 -based glass ceramics so as to achieve a high Wrec of 12.04 J cm-3 with a high η of 81.1% and an ultrahigh Wd of 11.98 J cm-3 with a superb Pd of 973 MW cm-3 . This work demonstrates a feasible route to obtain glass ceramics with an outstanding energy storage performance and proves the enormous potential of glass ceramics in high and pulsed power applications.

Analysis and Design of a Pulsed Power Generator for a Low-Energy Magnetic Pulse Welding System

Magnetic pulse welding (MPW) is a joining method that uses Lorentz force generated from an electromagnetic field. This method not only has the advantage of not causing thermal deformation of the material and no by-products compared to the method of joining by melting by heat but also enables the joining of dissimilar metals rather than the joining of the same metal. Joining dissimilar metals can reduce the weight of mechanical devices and apply them to various fields. Recent research on MPW has focused on the characteristics of bonding according to the material or structure of metal rather than on pulse power research that generates the main factor of operation. However, in the operation of MPW, a Lorentz force is generated by the induced current caused by the electromotive force created in the flyer tube and the external magnetic field in the actuator. Therefore, it is necessary to analyze and optimize the pulse power to improve reliability and to miniaturize the system to expand the MPW utilization range. In this paper, we analyzed MPW operation according to a section of the pulse power output waveform. A condition for obtaining the maximum current in the flyer tube was proposed, and a plateau-shaped waveform was derived as an ideal output waveform capable of maintaining the Lorentz force. Through analysis, the proposed pulse power device is designed as a pulse-forming network (PFN) that generates a plateau output waveform. The design specification is that the circuit of PFN (type E) is designed so that the output waveform is pulse width 10 (μs) and the maximum output current is 100 (kA), and it is verified by simulation.

Prominent energy storage density and efficiency of Na0.5Bi0.5TiO3‐based ceramics via multiscale amelioration strategy

AbstractEco‐friendly ceramic capacitors gradually become an important section of pulsed power devices. However, the synchronous realization of ultra‐high energy storage density (Wrec &gt; 6 J/cm3) and efficiency (η &gt; 90%) is difficult. Thus, a novel multiscale amelioration strategy in Na0.5Bi0.5TiO3‐based ceramics is proposed to achieve ultra‐high energy storage density and efficiency. The multiscale amelioration strategy for (Na0.5Bi0.47La0.03)0.94Ba0.06TiO3 (NBLBT) ceramic focuses on grain size, bandgap width, and dielectric relaxor behavior, which can be regulated by introducing Sr(Al0.5Nb0.25Ta0.25)O3 (SANT). On the one hand, the refined grain size and increased bandgap width are conducive to improving the breakdown strength. On the other hand, the optimized dielectric relaxation behavior is beneficial to suppress the remanent polarization. Accordingly, an ultrahigh Wrec = 6.89 J/cm3 and η = 90.1% are simultaneously achieved in 0.84NBLBT‐ 0.16SANT ceramic. In addition, the sample synchronously possesses excellent thermal and frequency stability (a variation within 5% in Wrec and η), transient discharge rate of t0.9 ∼ 78.8 ns and a high‐power density of PD ∼ 114.5 MW/cm3. This study provides an effective strategy to further develop pulsed power devices.

Comprehensive energy-storage performance enhancement in relaxor anti-ferroelectrics via strengthening local polarization

Lead-free dielectric capacitors with excellent energy-storage performance have gained much attention for their remarkable potential applications in pulsed power electronic systems and devices. However, the large recoverable energy-storage density Wrec is usually accompanied with low efficiency η, hindering their practical applications. Such performance deterioration occurs because the large polarization is generally linked with strong reversal hysteresis, making the synergetic optimization of energy-storage density and efficiency a great challenge. Here we develop a strategy of constructing strengthened local polarization in the lead-free relaxor anti-ferroelectric ceramics 0.9NaNbO3-0.1Bi(Ni2/3Nb1/3)O3 by carefully manipulating the microstructures, the ultrahigh Wrec ∼ 11.2 J/cm3 and large η ∼ 90.5 % have been simultaneously achieved. Moreover, superior charge/discharge performances (power density PD ∼ 548 WM/cm3, discharge speed t0.9 ∼ 27 ns) and outstanding temperature (up to 160 °C) and cycling (up to 106) stabilities are also ensured. The excellent overall properties are mainly attributed to the stabilized antiferroelectric phase, the strong relaxation characteristic, as well as the enhanced local polarization in the polar nano-regions (PNRs) caused by the introduction of Bi(Ni2/3Nb1/3)O3. This work not only provides a lead-free system with remarkable energy-storage performance that demonstrates great potential in the application field of high-power pulse electronic devices, but also proposes a convenient and efficient strategy to design new dielectric materials with excellent energy-storage performance.

The effect of current rise time on the acceleration of thick flyers to hypervelocities using an electric gun

The electric gun is a projectile launcher which utilises both the rapid expansion of an ohmically heated exploding foil and strong electromagnetic forces to accelerate an insulating flyer up to 20 km/s. The gun’s acceleration mechanism is highly efficient at converting stored electrical energy in the pulsed-power device driving the load to kinetic energy in the flyer, with values of up to 25% reported (Osher et al., 1990). This high efficiency would allow capacitor banks to use less energy than conventional drives to generate higher pressure states in materials of interest to extreme state research. Despite its promising efficiency, the electric gun is rarely used, as the process of launching flyers above 0.5 mm thickness in this manner is highly variable, often resulting in uncontrolled launch characteristics and premature failure of the flyer. The gun is also difficult to optimise without use of a sophisticated multi-physics hydrocode, further limiting its take-up. This work presents experimental results from the successful launch of 24 × 24 mm flyers up to 2.0 mm thick to 10 km/s using an electric gun load on 1.2 MJ pulsed-power device: Machine 3. In combination with results from a 0D model, these findings are used to identify the mechanism for the destruction of thick flyers accelerated using electric guns, including strategies for mitigating their break-up. The results support the existing idea that flyer failure can be avoided by limiting the maximum pressure within the flyer. They also reveal a second mechanism by which the flyer integrity can be maintained when the current rise time is longer than the flight time; high pressures in thick flyers caused their density to remain high enough to prevent the driving foil plasma from breaking through, averting their disassembly. This second mechanism provides a route to accelerate thick electric gun flyers to higher velocities with efficiencies up to around 9% whilst lengthening the shock duration on impact, broadening the gun’s potential applications in extreme state research.

Antiferroelectric ceramic capacitors with high energy-storage densities and reduced sintering temperature

Field-driven transition from antiferroelectric (AFE) to ferroelectric (FE) states has gained extensive attention for microelectronics and energy storage applications. High dielectric-breakdown-strength (DBDS) for a given material is a necessity to attain full capacity of electrical energy storage. An approach to increasing energy performances is to modulate the related materials to own a higher phase transition electric field (EFE-AFE) using elemental dopants. In this case, Cd2+ was selected as the dopant at A-site in the Pb0.97La0.02Zr0.50Sn0.45Ti0.05O3 ceramics to tailor this EFE-AFE value due to the ionic difference enhanced antiferroelectricity. Surprisingly, the doped ceramics increased EFE-AFE by half, DBDS by 16 %, and maintained energy storage efficiency η of over 85 %, providing a way to improve energy storage density. It is worth mentioning that while the performance has been improved, the sintering temperature has been reduced by 170 °C. At the same time, the ceramics maintain good temperature stability, extremely fast discharging speed and discharging energy storage density, indicative of a promising choice in pulse power devices.

Bayesian inferences of electrical current delivered to shocked transmission lines

Small radius Bdot measurements of electrical current delivered by pulsed power devices are routinely compromised by electrode/convolute plasmas endemic to multiterawatt transmission lines. Inferences of delivered current unaffected by these issues have recently been obtained by numerically optimizing consistency between model predictions and local experimental velocimetry data, but these are only unique for shockless velocity profiles. Here, we describe a more general Bayesian method capable of inferring current despite the presence of shocks. Additionally, we describe uncertainty estimates and use of the technique on experimental data. This technique is the first to provide uncertainty estimates on the full current trace delivered to an inertial confinement fusion target.

Designing a new KBT-based binary solid solution as a candidate for dielectric energy storage materials

Dielectric energy storage capacitors offer great potential in pulsed power devices due to the high power density and fast charging-discharging rate. Designing a host material with high field-induced polarization is of importance for developing dielectric energy storage materials via further composition modulation. In this paper, we compare the microstructure, dielectric, and ferroelectric properties as well as the energy storage performance of samples K1/2Bi1/2TiO3(KBT), 75KBT-25BiFeO3 (KBTF25), and 88KBT-12Bi0.85Nd0.15FeO3 (KBNTF12) in detail. It is found that, among three samples, sample KBNTF12 possesses the most complex local structure coexisting of a four-distortions with different polarities; meanwhile, sample KBNTF12 behaves as a strong relaxor, thus giving a high field-induced polarization. Besides, sample KBNTF12 realizes the highest electric breakdown strength Eb among three samples, which is resorted to the highest resistivity of grain boundary. Highest ΔP and Eb of sample KBNTF12 among three samples render it achieve ultrahigh stored energy density Ws of 6.94 J/cm3, high recoverable energy density Wr of 5.23 J/cm3, and high efficiency η of 75.4%. Our work suggests that 88KBT-12BNF binary composition be an optimal candidate for dielectric energy storage ceramics.

AgNbO3-Based Multilayer Capacitors: Heterovalent-Ion-Substitution Engineering Achieves High Energy Storage Performances.

The demand for miniaturization and integration in next-generation advanced high-/pulsed-power devices has resulted in a strong desire for dielectric capacitors with high energy storage capabilities. However, practical applications of dielectric capacitors have been hindered by the challenge of poor energy-storage density (Urec) and efficiency (η) caused by large remanent polarization (Pr) and low breakdown strength (BDS). Herein, we take a method of heterovalent ion substitution engineering in combination with the multilayer capacitor (MLCC) technology and thus achieve a large maximum polarization (Pmax), zero Pr, and high BDS in the AgNbO3 (AN) system simultaneously and obtain excellent Urec and η. The substitution of Sm3+ for Ag+ in SmxAN+Mn MLCCs at x ≥ 0.01 decreases the M1-M2 phase transition temperature, and the antiferroelectric (AFE) M2 phase appears at room temperature, which is beneficial to achieving a low Pr value. Due to the low Pr value and high BDS ∼ 1300 kV·cm-1, an excellent Urec ∼9.8 J·cm-3 and PD,max ∼ 34.8 MW·cm-3 were achieved in SmxAN+Mn MLCCs at x = 0.03. The work suggests a paradigm that can enhance the energy storage capabilities of AFE MLCCs to meet the demanding requirements of advanced energy storage applications.

Multistage phase transition induced excellent capacitive energy storage performances in (Pb,La,Sr)(Zr,Sn)O3 antiferroelectric ceramics

The applications of dielectric capacitors are essential for modern pulsed-power and high-power electronic devices. Antiferroelectric ceramics have garnered much attention as promising materials for capacitive energy storage on account of their ultrahigh recoverable energy density (Wrec). However, the relatively high energy loss originating from electric field induced antiferroelectric-ferroelectric (AFE-FE) phase transition results in low energy storage efficiency (η). Herein, the La3+ ions incorporated (Pb0.98Sr0.02)(Zr0.85Sn0.15)O3 antiferroelectric ceramics were explored to obtain stable antiferroelectric phase and trigger a unique multistage AFE-FE(Ⅰ)-FE(Ⅱ) phase transition simultaneously. Consequently, this strategy led to the achievement of an ultrahigh Wrec of 13.9 J/cm3 and an enhanced η of 80.4% in the optimal composition. Notably, these ceramics have also demonstrated exceptional thermal reliability of Wrec and η in a wide temperature range, outperforming other previously reported PbZrO3-based ceramics. These results offer an efficient approach to promote the capacitive energy storage behavior in antiferroelectric ceramics.

Ultrahigh Energy-Storage Density of BaTiO3-Based Ceramics via the Interfacial Polarization Strategy.

Lead-free dielectric capacitors are excellent candidates for pulsed power devices. However, their low breakdown strength (Eb) strongly limits their energy-storage performance. In this study, Sr0.7Bi0.2TiO3 (SBT) and Bi(Mg0.5Hf0.5)O3 (BMH) were introduced into BaTiO3 (BT) ceramics to suppress interfacial polarization and modulate the microstructure. The results show that the introduction of SBT and BMH increases the band gap width, reduces the domain size, and, most importantly, successfully attenuates the interfacial polarization. Significantly enhanced Eb values were obtained in (1 - x)(0.65BaTiO3-0.35Sr0.7Bi0.2TiO3)-xBi(Mg0.5Hf0.5)O3 (BSBT-xBMH) ceramics. Meanwhile, the interfacial polarization was reduced to near zero in the sample with x = 0.10, achieving an ultrahigh Eb (64 kV/mm) and a very large recoverable energy-storage density (Wrec ≈ 9.13 J/cm3). In addition, the sample has excellent thermal stability (in line with EIA-X7R standards) and frequency stability. These properties indicate that the BSBT-0.10BMH ceramic holds promising potential for the application of pulsed power devices.

Factors and Underlying Mechanisms That Influence the Repetitive Breakdown Characteristics of Corona-Stabilized Switches

The corona-stabilized switch has the potential to be a high repetition rate pulsed-power switching device, but there has been limited investigation into its repetitive breakdown stability and insulation recovery characteristics. Repetitive breakdowns of gas are characterized by a memory effect, where the subsequent breakdown process is inevitably influenced by the preceding one. However, there are still some issues that require further exploration in the current research on the mechanism of memory effect on repetitive breakdown characteristics. To clarify the factors and mechanisms that affect the repetitive breakdowns of corona-stabilized switches, this paper introduced optical observation methods into the experimental investigation. Through optical–electrical coupled diagnosis, the repetitive breakdown stability and insulation recovery performance of corona-stabilized switches under different working conditions and repetition frequencies were analyzed. The monotonic promoting effect of corona stabilization on switch insulation strength recovery is proposed as well as the non-monotonic and complex regulatory mechanism of corona stabilization on repetitive breakdown stability. The research results provide a theoretical and practical basis for clarifying the mechanism of repetitive corona-stabilized breakdowns and optimizing the design of corona-stabilized switches.

Influence of frequency on the partial discharge characteristics of biaxially oriented polypropylene film under nanosecond pulse voltage

Partial discharge (PD) is one of the key factors leading to premature insulation failure of film capacitors used in pulse power devices. To study the effect of frequency on the PD characteristics of biaxially oriented polypropylene (BOPP) film, a sphere-plate electrode was used to simulate defects of the air gap between the film layers. PD experiments of the BOPP film were carried out under 1, 10, 100, 500 Hz, and 1 kHz with a rising edge of 65 ns and a pulse width of 300 ns. The results show that the repetitive partial discharge inception voltage (RPDIV), the number of discharges, the rising stage discharge (RSD) amplitude, and the falling stage discharge (FSD) time-lag, all show an increase and then decrease with increasing pulse frequencies and reach a maximum value at a pulse frequency of 100 Hz. Moreover, the FSD discharge amplitude and the RSD discharge time-lag increase with an increasing pulse frequency. From the perspective of initial electron generation, the quantitative mathematical relationship between PD characteristics (RPDIV, PD amplitude, PD number, and PD time-lag) and frequency was established based on the Fowler–Nordheim field emission effect for the first time, which can reflect the influence of frequency on the memory effect and the development process of PD. The results can provide an experimental basis and a mechanistic explanation for the evaluation of PD characteristics for film capacitors under nanosecond pulse voltage.

Relaxor antiferroelectric-relaxor ferroelectric crossover in NaNbO3-based lead-free ceramics for high-efficiency large-capacitive energy storage

Relaxor ferroic dielectrics have garnered increasing attention in the past decade as promising materials for energy storage. Among them, relaxor antiferroelectrics (AFEs) and relaxor ferroelectrics (FEs) have shown great promise in term of high energy storage density and efficiency, respectively. In this study, a unique phase transition from relaxor AFE to relaxor FE was achieved for the first time by introducing strong-ferroelectricity BaTiO3 into NaNbO3-BiFeO3 system, leading to an evolution from AFE R hierarchical nanodomains to FE polar nanoregions. A novel medium state, consisting of relaxor AFE and relaxor FE, was identified in the crossover of 0.88NaNbO3–0.07BiFeO3–0.05BaTiO3 ceramic, exhibiting a distinctive core-shell grain structure due to the composition segregation. By harnessing the advantages of high energy storage density from relaxor AFE and large efficiency from relaxor FE, the ceramic showcased excellent overall energy storage properties. It achieved a substantial recoverable energy storage density Wrec ∼ 13.1 J/cm3 and an ultrahigh efficiency η ∼ 88.9%. These remarkable values shattered the trade-off relationship typically observed in most dielectric capacitors between Wrec and η. The findings of this study provide valuable insights for the design of ceramic capacitors with enhanced performance, specifically targeting the development of next generation pulse power devices.

Optimization Research of Pulse Power Device Based on Road-Field-Particle Collaborative Simulation

Optimization Research of Pulse Power Device Based on Road-Field-Particle Collaborative Simulation

Effect of anode shape on neutron and x-ray emission in dense plasma focus

The neutron and x-ray production is investigated in various pulse-power devices for a deeper understanding of the ion and electron acceleration mechanisms and the application of pulsed neutron sources. We present the extensive results from an anode shape experiment carried out on the PFZ-200 plasma focus device. The various shapes of anodes were tested, including cylinders, tapers, or rounded tips. The experimental shots with a peak current above 200 kA were performed in pure deuterium working gas at 280–600 Pa pressure to obtain maximal neutron yield for each anode shape. The average neutron yields are in the range of (1–2) ×108 neutrons/shot. Outstanding findings about x-ray emission were obtained with the group of tapered anode tips. Using the scintillation detectors shielded by 5 cm thick lead bricks, we obtained the hard x-ray signals with photons exceeding 600 keV energy. Such relatively high x-ray energy indicates the optimized conditions for electron and ion acceleration. At the same time, the individual shots have been well reproducible. Therefore, we were able to study plasma dynamics with the schlieren images taken at different times at different shots.

Improvement in dielectric properties and energy storage performance of barium strontium niobate glass ceramics by Sm2O3 addition

High power density and high energy density glass ceramics have important applications in the field of miniaturized, lightweight and integrated pulsed power devices. Barium strontium niobate glass ceramics with different additive amount of Sm2O3 were successfully prepared. The effects of different additions of Sm2O3 on the phase composition, dielectric properties, breakdown strength, interfacial polarizations and energy storage properties of glass ceramics were investigated. The results of phase structure show that Ba0.5Sr0.5Nb2O6 of tungsten bronze structure and BaAl2Si2O8 two phases are precipitated from the glass matrix. The optimum Sm2O3 addition can increase the Ba0.5Sr0.5Nb2O6 phase content of tungsten bronze structure in the glass ceramics, thus increasing the dielectric constant of strontium barium niobate glass ceramics. A moderate amount of Sm2O3 addition improves the microstructure of the barium strontium niobate glass ceramics and reduces the interfacial activation energy of the glass ceramics, thus increasing the breakdown strength of the glass ceramics. For 3 mol% Sm2O3 addition, the breakdown strength of the glass ceramics reaches 1590 kV/cm with a corresponding dielectric constant of 98.4 and a maximum energy storage density of 12.44 J/cm3, which is 2.62 times higher than that of the barium strontium niobate glass ceramics without Sm2O3 addition. It is concluded that the increased energy density of glass ceramics can be attributed to the fact that the appropriate additive amount of Sm2O3 (1–3 mol%) increases the crystallinity of the glass ceramics and at the same time reduces the interfacial activation energy of the glass ceramics, thus increasing the dielectric properties of the glass ceramics with respect to the breakdown strength.

Phase transition of potassium sodium niobate under high pressures

As a piezoelectric material, K0.5Na0.5NbO3 (KNN) has broad application prospects in ultrasonic transducers, sensors, and biomedicine areas. Its structure information under high pressures is of great significance for guiding device design. In this study, the high-pressure structural evolution of KNN has been studied. Two structural phase transitions were revealed by high-pressure Raman spectrum. The phase transition boundary was found by Raman vibration mode analysis, with transformation ranges of 2.5–4.6 and 6.8–9.4 GPa. The phase structures were determined by in situ neutron diffraction, with a phase transformation path of orthogonal Amm2 (O) → tetragonal P4mm (T) → cubic Pm3¯m (C) structure at high pressures. Synchrotron x-ray diffraction further confirmed the phase transformation path. During the processes of phase transitions, the path of Nb atom was clearly described as moving toward [1¯01] and then [100] direction. An output power density of KNN ceramic devices was comparable to that of commercially available PZT 95/5. The density of KNN ceramic is approximately half that of PZT 95/5, which means a significant advantage in terms of weight reduction and miniaturization of equipment in global demand. The phase transition of ferroelectric materials under high pressures provides scientific guidance for the development of high-power pulse power devices.

Enhanced energy storage and fast discharge properties of BaTiO3-Bi(Ni0.5Zr0.5)O3 ceramics modified by (Bi0.5Na0.5)0.7Sr0.3TiO3

ABSTRACT Relaxed ferroelectric ceramics with good energy storage stability, high energy storage density and efficiency, and high charge/discharge rates have shown great potential for commercial applications. In this paper, 0.85[0.9BaTiO3 −0.1Bi(Ni0.5Zr0.5)O3]−0.15(Bi0.5Na0.5)0.7Sr0.3TiO3 ceramic was prepared via a solid – phase reaction method by doping (Bi0.5Na0.5)0.7Sr0.3TiO3 into 0.9BaTiO3 > −0.1Bi(Ni0.5Zr0.5)O3; it exhibited excellent energy storage performance values: Wrec = 2.87 J/cm3 and η = 88.10%. Charging and discharging tests were conducted to evaluate the feasibility of the ceramic for practical applications in energy – storage devices; it displayed an ultrafast discharge rate of 1.16 μs. In addition, the developed ceramic has good frequency stability (1–120 Hz) and high temperature stability (40–160°C). This excellent energy storage performance indicates that the ceramic is a suitable candidate for pulse power devices.