Advanced Pulsed Power Research Articles

Effective strategy to improve energy storage properties in lead-free (Ba0.8Sr0.2)TiO3-Bi(Mg0.5Zr0.5)O3 relaxor ferroelectric ceramics

Although relaxor ferroelectrics (RFEs) have received considerable attention in advanced pulsed power capacitor systems (APPCSs) due to their numerous advantages, it remains difficult to achieve comprehensive outstanding energy storage performance (ESP) owing to the trade-offs among recoverable energy density (Wrec), energy efficiency (η) and thermal stability. In this work, we proposed a collaborative optimization strategy for improving the ESP of (Ba0.8Sr0.2)TiO3 (BST)-based RFE ceramics, i.e., the introduction of Bi(Mg0.5Zr0.5)O3 (BMZ) and the use of viscous polymer process (VPP). The former obstructs the long-range ferroelectric order, induces high dynamic polar nanoregions and broadens temperature stabilized platform, thus alleviating the polarization hysteresis and increasing the energy efficiency. The latter progressively dilute pore concentration and thins the sample to ∼70 μm, which can greatly improve breakdown strength. As a result, exceptional ESP parameters are simultaneously achieved in 0.85BST-0.15BMZ ceramics by VPP (BMZ15VPP), which exhibit ultrahigh Wrec (10.3 J/cm3) and high η (88%) under 720 kV/cm while maintaining stable temperature stability. It is also noteworthy that a superior current density of 800 A/cm2 and a power density of 140 MW/cm3 are obtained. The overall excellent performance implies the competitiveness of BMZ15VPP in APPCSs and the feasibility of this strategy in designing compositive high ESP ceramic systems.

Achieving ultra-short discharge time and high energy density in lead-based antiferroelectric ceramics by A-site substitution

Antiferroelectric (AFE) ceramic capacitors are promising candidates for energy storage applications in advanced pulsed power capacitors (APPCs) due to the high-power density. Nevertheless, the incompatibility between discharge time and energy storage density limits their practical application in APPCs. Herein, we present ultra-short discharge time and high energy density performances of (Pb1-1.5xSmx)(Zr0.6Sn0.4)O3 AFE ceramics by A-site Sm modification strategy. Ultrafast discharge rate (t0.9) of ∼ 57.1 ns and high recoverable energy density of ∼ 11.2 J/cm3 (energy efficiency of 85.1%) at 400 kV/cm are achieved simultaneously in (Pb0.94Sm0.04)(Zr0.6Sn0.4)O3 ceramic. The t0.9 of AFE ceramics directly related to phase-switching fields, which is confirmed by variable electric field test. Sm modification is contribution to enhancing the interaction among the ions by reduction of tolerance factor, and strengthening phase-switching fields, leading to improving the stability of AFE state, which is confirmed by XRD, Raman, SEM, XPS profiles and P-E curves. As a result, the t0.9 is decreased from 87.2 to 51.1 ns, corresponding to large discharge energy density (∼9.7 J/cm3) owing to high breakdown strength by refining average grain sizes with increasing Sm content. Meanwhile, this ceramic has good fatigue resistance in terms of frequency and temperature. These results would provide a reliable strategy for the design and application of APPCs.

High-Performance PbZrO3-based antiferroelectric multilayer capacitors based on multiple enhancement strategy

Antiferroelectric (AFE) materials are thought to be one of the most promising candidates for energy storage application owing to their large polarization difference between maximum polarization and remanent polarization originating from unique electric field-induced phase transition, but the large polarization hysteresis leads to an inferior energy efficiency, which restricts their applications in advanced pulsed power devices. Herein, we propose a multiple enhancement strategy of composition and structural modification to solve this problem. The (Pb0.875La0.05Sr0.05)(Zr0.695Ti0.005Sn0.3)O3 (PLSZTS) antiferroelectric ceramic and corresponding multilayer ceramic capacitor (MLCC) are fabricated. A low hysteresis is obtained via composition optimization. Moreover, multilayer ceramic constructing improves significantly breakdown strength (BDS) due to decreased thickness of dielectric layer. An ultrahigh recoverable energy density (Wdis) of 19.9 J/cm3, together with a high energy efficiency (η) of 96.4% are achieved synchronously at an electric field of 85 kV/mm. In addition, the studied MLCCs also possess outstanding discharge energy storage properties with a high discharge energy density (Wdis) of 15.4 J/cm3 and a large power density (PD) of 170.5 MW/cm3, a wide temperature range of 20–120 °C, and strong fatigue endurance after 3000 cycles. The present research results not only offer a potential candidate for high-power energy storage devices, but also, more importantly, develop a universal approach for optimizing the overall energy storage performance.

Concurrent achievement of giant energy density and ultrahigh efficiency in antiferroelectric ceramics via core–shell structure design

The boom in high-power-density electronics and advanced pulsed power systems has led to a requirement for high-energy-density dielectric capacitors, for which the key enabler is the availability of dielectric materials with high energy densities and high efficiencies. Although antiferroelectric ceramics are promising dielectric materials with high energy densities, they have low efficiencies. In this study, we address this problem through the core–shell structure design. A phase-field model is developed by considering the core as antiferroelectric and the shell as linear dielectric, and the polarization hysteresis loops are determined. The results show that the polarization–electric field loop of the core–shell sample is slanted, with a delayed saturation polarization, decreased maximum polarization, and declined hysteresis loss compared with the pure sample. This phenomenon becomes more distinct with increasing shell fraction and decreasing shell permittivity, and vanished hysteresis is achieved in samples with a high shell fraction and a low shell permittivity. Through deconvolution, it is determined that the underlying mechanism of energy storage is the difference in the antiferroelectric polarization contribution of various shell parameters. It is found that a giant energy density of 15.5 J/cm3 and an ultrahigh efficiency of 99.7% at the saturation polarization can be achieved concurrently for a certain core–shell sample; these values considerably exceed the corresponding values (5.0 J/cm3 and 52.8%) for the pure sample. The findings of this study can serve as guidance for engineering core–shell structures, thus paving the way for enhancing the energy-storage performance of antiferroelectric ceramics.

Ultrahigh Energy Storage Density and High Efficiency in Lead-Free (Bi0.9Na0.1)(Fe0.8Ti0.2)O3-Modified NaNbO3 Ceramics via Stabilizing the Antiferroelectric Phase and Enhancing Relaxor Behavior.

Dielectric capacitors have attracted growing attention because of their important applications in advanced high power and/or pulsed power electronic devices. Nevertheless, the synergistic enhancement of recoverable energy storage density (Wrec > 10 J/cm3) and efficiency (η > 80%) is still a great challenge for lead-free dielectric bulk ceramics. Herein, by introducing complex perovskite compound (Bi0.9Na0.1)(Fe0.8Ti0.2)O3 with a smaller tolerance factor into an NaNbO3 matrix (NN-BNFT), we have achieved and explored stable relaxor antiferroelectric ceramics with enhanced relaxor behavior. Of particular importance is the composition of 0.88NN-0.12BNFT, which exhibits a large electric breakdown strength Eb of 87.3 kV/mm, an ultrahigh Wrec of 12.7 J/cm3, and a high efficiency η of 82.5%, as well as excellent thermal reliability and an ultrafast discharge speed, resulting from the dense microstructure, the moderate dielectric constant, the reduced grain size, the dielectric loss, and the sample thickness. The outstanding energy storage properties of NN-BNFT display great promise in advanced dielectric capacitors for energy storage applications.

High energy storage and thermal stability under low electric field in Bi0.5Na0.5TiO3-modified BaTiO3-Bi(Zn0.25Ta0.5)O3 ceramics

Dielectric energy storage capacitors have been comprehensively investigated for application in advanced electronic systems. Compared to other types of ceramic capacitors, BaTiO3-BiMeO3 lead-free composite relaxor ferroelectric ceramics (where Me represents trivalent or trivalent composite ion) are excellent dielectric energy storage candidates in pulsed power fields. However, the properties of most existing BT-based energy storage ceramics are not satisfactory in some practical aspects, and feasible guidance on efficient composting material systems with large recoverable energy storage density (Wrec) for ultralow electric fields is lacking. Herein, for the first time, lead-free relaxor ferroelectric (1-x)[0.9BaTiO3-0.1Bi(Zn0.25Ta0.5)O3]-xBi0.5Na0.5TiO3 ceramics with x = 0, 0.1, 0.2, 0.3, and 0.4 were synthesized via composite strategy using the traditional solid-state process. The used strategy combined the complementary advantages of both BT-BZT and BNT to greatly increase the saturation polarization (Ps) and shift the stable temperature range of permittivity to high-temperature region, achieving higher energy storage density and improved temperature stability. Optimum energy storage performances with a high Wrec of 4.18 J/cm3 and comparatively high η of 84.01% were simultaneously achieved in the relatively low electric field of 230 kV/cm. Moreover, the ceramic obtained at x = 0.3 showed excellent temperature stability with the change rate of Wrec < 5% and η < 6% throughout a broad temperature range (20 °C ∼ 170 °C). This ceramic (x = 0.3) simultaneously possesses superior pulse performance, exhibiting the t0.9 of 232 ns and Wdis of 2.51 J/cm3. Overall, the employed composite strategy design is effective for obtaining energy storage capacitors with excellent performance for future advanced pulsed power devices.

Synergy of a Stabilized Antiferroelectric Phase and Domain Engineering Boosting the Energy Storage Performance of NaNbO3-Based Relaxor Antiferroelectric Ceramics.

Relaxor antiferroelectric (AFE) ceramic capacitors have drawn growing attention in future advanced pulsed power devices for their superior energy storage performance. However, state of the art dielectric materials are restricted by desirable comprehensive energy-storage features, which have become a longstanding hurdle for actual capacitor applications. Here, we report that a large energy density Wrec of 5.52 J/cm3, high efficiency η of 83.3% at 560 kV/cm, high power density PD of 114.8 MW/cm3, ultrafast discharge rate t0.9 of 45 ns, and remarkable stability against temperature (30-140 °C)/frequency (5-200 Hz)/cycles (1-105) are simultaneously achieved in 0.7 NaNbO3-0.3 CaTiO3 relaxor AFE ceramics via the synergy of stabilized AFE R phase and domain engineering in combination with breakdown strength enhancement. The structural origin for these achievements is disclosed by probing the in situ microstructure evolution by means of the first-order reversal curve method, piezoelectric force microscopy, and Raman spectroscopy. The highly dynamic polar nanoregions and stabilized AFE R phase synergistically generate a linear-like and highly stable polarization field response over a wide temperature and field scope with concurrently improved energy density and efficiency. This work offers a new solution for designing high-performance next-generation pulsed power capacitors.

Energy storage properties under moderate electric fields in BiFeO3-based lead-free relaxor ferroelectric ceramics

Achieving high overall energy-storage properties under moderate electric fields is of great significance for practical applications of energy-storage ceramic capacitors. In this work, an ultrahigh recoverable energy-storage density (Wrec) of ∼ 3.9 J/cm3 and a high energy-storage efficiency (η) of ∼ 80% are simultaneously achieved under a moderate electric field of 25 kV/mm in a new ternary lead-free relaxor ferroelectric (FE) ceramic of 1 wt.%Nb2O5-doped 0.46Bi1.02FeO3-0.29BaTiO3-0.25Bi0.5Na0.5TiO3 (BF-BT-BNT). Together with excellent thermal and frequency stability of Wrec = 1.68 ± 12%J/cm3, η = 90 ± 9%, 0.1–100 Hz; Wrec = 1.61 ± 6%J/cm3, η = 87 ± 5% within 30–170 °C, a large power density of PD ∼ 43.0 MW/cm3 and a fast discharge rate of t0.9 ∼ 45 ns, Nb2O5-doped BF-BT-BNT ceramics exhibit promising potentials for environment-friendly advanced pulsed power capacitors. Multiscale structure characterization reveals that the incorporation of Nb2O5 into BF-BT-BNT significantly increases the local structure disorder, leading to a heterogeneous nanodomain morphology. This makes the Nb2O5-doped BF-BT-BNT ceramic maintain a high maximum polarization, but obviously suppressed polarization hysteresis, thus responsible for significantly improved overall energy-storage properties.

Composition and Structure Optimized BiFeO3 -SrTiO3 Lead-Free Ceramics with Ultrahigh Energy Storage Performance.

Dielectric ceramic capacitors have attracted increasing attention as advanced pulsed power devices and modern electronic systems owing to their fast charge/discharge speed and high power density. However, it is challenging to meet the urgent needs of lead-free ceramics with superior energy storage performance in practical applications. Herein, a strategy for the composition and structural modification is proposed to overcome the current challenge. The lead-free ceramics composed of BiFeO3 -SrTiO3 are fabricated. A low hysteresis and high polarization can be achieved via composition optimization. The experimental results and finite element simulations indicate that the two-step sintering method significantly influences the decrease in the grain size and improvement in the breakdown strength (EBDS ). A high EBDS of ≈750kV cm-1 accompanied by a large maximum polarization (≈40 µC cm-2 ) and negligible remanent polarization (<2 µC cm-2 ) contribute to the ultrahigh energy density and efficiency values of the order of 8.4 J cm-3 and ≈90%, respectively. Both energy density and efficiency exhibit excellent stability over the frequency range of 1-100Hz and temperatures up to 120°C, along with the superior power density of 280 MW cm-3 , making the studied BiFeO3 -SrTiO3 ceramics potentially useful for high-power energy storage applications.

Remarkably enhanced dielectric stability and energy storage properties in BNT\u2014BST relaxor ceramics by A-site defect engineering for pulsed power applications

Lead-free bulk ceramics for advanced pulsed power capacitors show relatively low recoverable energy storage density (Wrec) especially at low electric field condition. To address this challenge, we propose an A-site defect engineering to optimize the electric polarization behavior by disrupting the orderly arrangement of A-site ions, in which {rm{B}}{{rm{a}}_{0.105}}{rm{N}}{{rm{a}}_{0.325}}{rm{S}}{{rm{r}}_{0.245 - 1.5x}}{_{0.5x}}{rm{B}}{{rm{i}}_{0.325 + x}}{rm{Ti}}{{rm{O}}_3} ({rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}}, x = 0, 0.02, 0.04, 0.06, and 0.08) lead-free ceramics are selected as the representative. The {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} ceramics are prepared by using pressureless solid-state sintering and achieve large Wrec (1.8 J/cm3) at a low electric field (@110 kV/cm) when x = 0.06. The value of 1.8 J/cm3 is super high as compared to all other Wrec in lead-free bulk ceramics under a relatively low electric field (< 160 kV/cm). Furthermore, a high dielectric constant of 2930 within 15% fluctuation in a wide temperature range of 40–350 °C is also obtained in {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} (x = 0.06) ceramics. The excellent performances can be attributed to the A-site defect engineering, which can reduce remnant polarization (Pr) and improve the thermal evolution of polar nanoregions (PNRs). This work confirms that the {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} (x = 0.06) ceramics are desirable for advanced pulsed power capacitors, and will push the development of a series of Bi0.5Na0.5TiO3 (BNT)-based ceramics with high Wrec and high-temperature stability.

(Bi0.5Na0.5)TiO3-based relaxor ferroelectrics with medium permittivity featuring enhanced energy-storage density and excellent thermal stability

High energy density, efficiency and thermal stability of energy-storage properties are extremely pivotal for the application of dielectric ceramics in advanced pulsed power systems. In this work, we utilize a composition-driven strategy to induce polar nanoregions, refine grain size and adjust permittivity of (1-x)Bi0.5(Na0.9Li0.1)0.5TiO3-xSr(Al0.5Nb0.25Ta0.25)O3 ceramics. As a result, an extraordinary Wrec of 6.43 J/cm3 and high η of 88% are simultaneously obtained in the x = 0.16 composition. Meanwhile, the x = 0.16 sample also shows good frequency stability (5–100 Hz), cycle stability (105 cycles) and superior thermal stability (-55 ~ 225 ℃). The enhanced breakdown strength is analyzed by Weibull distribution and mainly attributed to the decreased average grain size. The typical relaxor behavior is reflected by the broadened and diffused Raman spectra as well as the dispersive and temperature-stable dielectric curves. The existence of dynamic polar nanoregions as confirmed by piezoresponse force microscopy measurements enables the nearly hysteresis-free polarization–electric field response and the related frequency and cycle stability. The mitigated polarization saturation is related to the field-insensitive moderate permittivity and will be conducive to the energy-storage properties at elevated electric field. In addition, the temperature-dependent Raman spectra and the slightly fluctuated ΔP (Pm - Pr) value over the whole temperature range reflect the temperature-stable energy-storage properties. Hence, the current work may provide some novel perspectives for designing dielectric ceramics with enhanced energy-storage properties.

Ultra-fast charge-discharge and high energy storage density realized in NaNbO3–La(Mn0.5Ni0.5)O3 ceramics

Lead-free antiferroelectric (AFE) NaNbO3 (NN) is one of promising materials for dielectric capacitors, but the recoverable energy-storage density and efficiency get restrained owing to huge remanent polarization and limited dielectric breakdown field strength. In this work, a variety of NN based lead-free bulk (1-x)NaNbO3-xLa(Mn0.5Ni0.5)O3 (abbreviated as (1-x)NN-xLMN, x = 0, 0.05, 0.10, 0.15, 0.20) ceramics were designed using a solid-state synthesis method. Remarkably, an ultra-fast charge-discharge speed 47 ns and an acceptable recoverable energy-storage density Wrec ~1.77 J/cm3 with a high efficiency η = 77% were obtained under the Eb of 200 kV/cm at x = 0.05. The superior energy storage performance is attributed to the regulation of domain size and voltage resistance by special ions substitution of A and B sites. This work not only proposes an efficient strategy to realize high recoverable energy-storage density and efficiency, but also provide an candidate material for application of advanced pulsed power capacitors.

Breakdown strength and energy density enhancement in polymer-ceramic nanocomposites: Role of particle size distribution

Polymer-ceramic nanocomposites play a very promising role for energy-storage in high power electronics and advanced pulsed power systems, due to their extremely fast charge-discharge capability. The low energy density is the key factor hindering their application, for which large endeavors have been made in the modulation of the fraction, morphology, size, and dispersion of the particle fillers but small in that of the size distribution, which is critical for energy-storage performance. We first investigated the role of this based on simulated nanocomposites with controlled lognormal distributions via a generation algorithm devised in this work. Dielectric response, breakdown behavior and energy-storage performance were explored for distributions with different standard deviations (SD) and mean values (MV), which were solved with the energy equivalence basis and a phase-field dielectric breakdown model. With the decrease of SD and MV, the effective permittivity declines slightly with enhanced permittivity change, which was related with the enhanced local electric field with intensified fluctuation and should be originated from the major contribution of the polymer matrix from the local energy perspective; whereas improved nominal breakdown strength was achieved owing to the weakened local maximum electric field, which leads to distinctly increased nominal energy density despite the slight decline of the permittivity. Keeping the fillers within a narrow disperse outperforms employing super fine particles. This work demonstrates that enhancement in breakdown strength and energy density can be attained via particle size distribution modulation, paving a new way for the further improvement of the energy-storage performance of polymer-ceramic nanocomposites.

Significantly enhancing energy storage performances of flexible dielectric film by introducing poly(1,4-anthraquinone)

Polymer dielectrics have wide application in advanced electronic devices and pulsed power systems because of their easy processing, low cost, outstanding flexibility and high breakdown strength (Eb). However, the low energy density (Ue) of polymer dielectrics restricts the miniaturization and integration of dielectric capacitors. Herein, poly(1,4-anthraquinone) with rigid molecular chains was synthesized and introduced into poly(vinylidene fluoride) (PVDF). Benzene rings on the main chains and large steric hindrance in the side chains limit the intramolecular rotation and thus endow poly(1,4-anthraquinone) with rigid chain structure. Moreover, extended π system and delocalization of electrons minimize the energy of polymer chain, which gives poly(1,4-anthraquinone) more prominent durability and stability. The introduction of poly(1,4-anthraquinone) reduces the crystallite sizes of PVDF and strengthens Young’ modulus of the films. Consequently, both high Eb and Ue are achieved and increased by 170% and 62% compared with pristine PVDF, respectively. This research provides a new strategy to prepare PVDF-based dielectric film with superior energy storage performances.

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

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

Optimization of synergistic energy storage density and efficiency for eco-friendly (Na0.5Bi0.5)0.6Sr0.4TiO3-based relaxor ferroelectric ceramics

Inspired by increasing demand of advanced pulsed power capacitors, the development of lead-free dielectric ceramic capacitors with high energy storage density and temperature-insensitive performance are extremely crucial. Herein, the lead-free relaxor ferroelectric ceramics based on (1-x) (Na0.5Bi0.5)0.6Sr0.4TiO3- xSr0.7La0.2ZrO3 [abbreviated as (1-x)NBST-xSLZ] are prepared by the solid-state reaction route. The large recoverable energy density (Wrec) of 3.45 J/cm3 and efficiency (η) of 90.1% are simultaneously realized in 0.86NBST-0.14SLZ ceramic due to increased breakdown strength. Furthermore, both the Wrec and η of 0.86NBST-0.14SLZ ceramic display superior of thermal stability (20–180 °C), frequency stability (1–1000 Hz), and cycle stability (104) within a satisfactory range of variation. In addition, the 0.86NBST-0.14SLZ ceramic can also achieve a large current density (CD) of 625 A/cm2, an ultrahigh power density (PD) of 50 MW/cm3 and a fast discharge rate (τ0.90) of 160.8 ns at 160 kV/cm. These results demonstrate that the 0.86NBST-0.14SLZ ceramic could be a highly competitive and eco-friendly relaxor ferroelectric material for next-generation pulsed power capacitors.

Significantly enhanced dielectric breakdown strength of ferroelectric energy-storage ceramics via grain size uniformity control: Phase-field simulation and experimental realization

The utilization of ferroelectric ceramics in electrical energy storage has become a hot topic due to the urgent need for advanced pulsed power and high power energy storage applications. Much attention has been paid to achieving nanograined ferroelectric ceramics but little to the effect of grain size uniformity, which is critical for dielectric breakdown and reliability. We first investigated this effect via a model based on virtually constructed ceramic samples solved with the phase-field method. Ferroelectric ceramic samples with the same average grain size of typically 100 nm but different uniformity degrees by the variation of the standard deviation values of 83.7, 81.9, 80.1, and 78.7 were constructed via Voronoi tessellation based on a controlled seeding method. The effect of grain size uniformity on the dielectric breakdown was studied through a phase-field dielectric breakdown model. The results indicate that with the standard deviation decreasing, the dielectric breakdown strength is distinctly enhanced. Experimentally, BaTiO3-based ceramics with the same average grain size of 100 nm but different uniformity degrees were realized via conventional sintering and two-step sintering methods. The grain size uniformity of two-step sintered ceramics is greatly improved, which leads to the breakdown strength and discharge energy density of the two-step sintered ceramics about 50% and 100% larger than those of the conventionally sintered ones. This work demonstrates that significant enhancement in dielectric breakdown strength of ferroelectric energy-storage ceramics can be achieved via grain size uniformity control, shedding light on the meticulous design and fine tuning of the energy-storage properties of ferroelectric ceramics.

High energy storage and ultrafast discharge in NaNbO3-based lead-free dielectric capacitors via a relaxor strategy

Dielectric capacitors with decent energy storage and fast charge-discharge performances are essential in advanced pulsed power systems. In this study, novel ceramics (1-x)NaNbO3-xBi(Ni2/3Nb1/3)O3(xBNN, x = 0.05, 0.1, 0.15 and 0.20) with high energy storage capability, large power density and ultrafast discharge speed were designed and prepared. The impedance analysis proves that the introducing an appropriate amount of Bi(Ni0·5Nb0.5)O3 boosts the insulation ability, thus obtaining a high breakdown strength (Eb) of 440 kV/cm in xBNN ceramics. A high energy storage density (Wtotal) of 4.09 J/cm3, recoverable energy storage density (Wrec) of 3.31 J/cm3, and efficiency (η) of 80.9% were attained in the 0.15BNN ceramics. Furthermore, frequency and temperature stability (fluctuations of Wrec ≤ 0.4% over 5–100 Hz and Wrec ≤ 12.3% over 20–120 °C) were also observed. The 0.15BNN ceramics exhibited a large power density (19 MW/cm3) and ultrafast discharge time (~37 ns) over the range of ambient temperature to 120 °C. These enhanced performances may be attributed to the improved breakdown strength and relaxor behavior through the incorporation of BNN. In conclusion, these findings indicate that 0.15BNN ceramics may serve as promising materials for pulsed power systems.

Enhanced energy storage properties of Sr(Sc0.5Nb0.5)O3 modified (Bi0.47La0.03Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Excellent energy storage performance of dielectric capacitors is highly desired in all kinds of energy storage devices. In this study, Sr(Sc0.5Nb0.5)O3 was introduced to enhance the energy storage properties of (Bi0.47La0.03Na0.5)0.94Ba0.06TiO3 (BLNBT) ceramics. All ceramic samples were sintered densely, and the phase structure, microstructure, dielectric and ferroelectric properties were then systematically investigated. Two distinct dielectric anomaly peaks, which are detected from the dielectric properties as a function of temperature, suggest not only a phase transition, but also indicate typical relaxor features. The breakdown strength is significantly improved, and the polarization versus electric field hysteresis loops become slim with the increasing content of SSN. The optimum energy storage performance is achieved in 0.85BLNBT–0.15SSN ceramic with the recoverable energy density of 1.83 J/cm3 and energy efficiency of 82.32% under a moderate electric field of 185 kV/cm. The excellent energy storage performance of 0.85BLNBT–0.15SSN ceramic makes it a promising candidate material for advanced pulsed power capacitors.

Significantly enhanced energy storage density in sodium bismuth titanate-based ferroelectrics under low electric fields

Bi0.5Na0.5TiO3 (BNT)-based ferroelectrics have received more and more attention due to their environment-friendliness and large maximum polarization. Herein, the enhanced energy-storage properties of BNT-based ceramics were successfully prepared by introducing multi-ions (La3+, K+, Al3+, Nb5+, Zr4+) to improve the breakdown strength and simultaneously suppress the remnant polarization. An excellent discharge energy-storage density (Wd) of 3.24 J cm−3 and a high energy-storage efficiency (η) of 82 % under 200 kV cm-1 have been recorded for Bi0.44La0.06(Na0.82K0.18)0.5Ti0.90(Al0.5Nb0.5)0.08Zr0.02O3 ceramic. Meanwhile, the outstanding thermal stability with Wd of 1.84–1.96 J·cm−3 were also achieved in 25−125 °C at 140 kV cm-1. More importantly, piezoresponse force microscopy reveals that the threshold voltage for inducing long range order enhances while the stability of polar nanoregions (PNRs) on the nanoscale decreased with the increase of La doping amount, leading to more linear polarization behavior and higher energy-storage properties. These results promote the practical applications of BNT-based ferroelectrics in advanced pulsed power systems.