Lead-free Relaxor Ferroelectric Ceramics Research Articles

Enhanced temperature stability at DC-biased electric field in (Ba,Sr)0.82Bi0.12TiO3 lead-free energy-storage relaxor ferroelectric ceramics via superparaelectric engineering

Enhanced temperature stability at DC-biased electric field in (Ba,Sr)0.82Bi0.12TiO3 lead-free energy-storage relaxor ferroelectric ceramics via superparaelectric engineering

Enhanced low-field energy storage performance and dielectric stability in (Bi0.4Sr0.2K0.2Na0.2)(Ti1-xZrx)O3 high-entropy ceramics via B-site modification

The current global energy situation is tense, necessitating the development of high-efficiency, low-cost, and eco-friendly energy materials. In this study, a series of perovskite lead-free relaxor ferroelectric ceramics, denoted as (Bi0.4Sr0.2K0.2Na0.2)(Ti1-xZrx)O3 (BSKNT-xZr) were designed to enhance the storage performance. The findings indicate that all samples exhibit a single perovskite structure. As the Zr4+ content increases, the configurational entropy of the samples increases, the cell volume expands, and the hysteresis loops become finer, while maintaining a high maximum polarization (Pm) and effectively enhancing the energy storage performance. For the ceramic with x = 0.10, the energy density (Wtot), recoverable energy density (Wrec), and energy storage efficiency (η) values were determined to be 3.16 J/cm3, 2.67 J/cm3, and 84.3%, respectively, under an electric field of 230 kV/cm. Moreover, the introduction of Zr4+ reduces the relative permittivity and broadens the temperature range (ΔT) that simultaneously satisfies Δε/ε150°C ≤ ±15% and 0 ≤ tanδ ≤ 0.02. This investigation underscores the potential of BSKNT-xZr ceramics as high-performance, cost-effective, and environmentally friendly energy materials for addressing global energy requirements.

Large Room-Temperature Electrocaloric Effect in Lead-Free Relaxor Ferroelectric Ceramics with Wide Operation Temperature Range.

In order to obtain large room-temperature electrocaloric effect (ECE) and wide operation temperature range simultaneously in lead-free ceramics, we proposed designing a relaxor ferroelectric with a Tm (the temperature at which the maximum dielectric permittivity is achieved) near-room temperature and glass addition. Based on this strategy, we designed and fabricated lead-free 0.76NaNbO3-0.24BaTiO3 (NN-24BT) ceramics with 1wt.% BaO-B2O3-SiO2 glass addition, which showed distinct relaxor ferroelectric characteristics with strongly diffused phase transition and a Tm near-room temperature. Based on a direct measurement method, a large ΔT (adiabatic temperature change) of 1.3 K was obtained at room temperature under a high field of 11.0 kV mm-1. Additionally, large ECE can be maintained (>0.6 K@6.1 kV mm-1) over a broad temperature range from 23 °C to 69 °C. Moreover, the ECE displayed excellent cyclic stability with a variation in ΔT below ±7% within 100 test cycles. The comprehensive ECE performance is significantly better than other lead-free ceramics. Our work provides a general and effective approach to designing lead-free, high-performance ECE ceramics, and the approach possesses the potential to be utilized to improve the ECE performance of other lead-free ferroelectric ceramic systems.

High energy storage performance in SrZrO3-modified quaternary relaxor ferroelectric ceramics

Lead-free relaxor ferroelectric ceramics have attracted much attention in pulse power systems owing to their excellent energy storage performance and environmentally friendly characteristics. However, it is challenging to simultaneously achieve high energy storage density and efficiency in ferroelectric ceramics for practical applications. Herein, a novel optimization strategy is designed by introducing a linear dielectric SrZrO3 (SZ) with wide bandgap (Eg) into the BaTiO3-Bi0.5Na0.5TiO3-NaNbO3 (BT-BNT-NN) to form quaternary ceramics, disrupting long-range ferroelectric ordering and constructing weakly coupled polar nanoregions (PNRs). As a result, the recoverable energy density (Wrec) and energy storage efficiency (η) are simultaneously improved in (1-x) (BT-BNT-NN)-xSZ ceramics. At an electric field of 530 kV/cm, a Wrec of 3.37 J/cm3 and an η of 82.5 % were optimally achieved at x = 0.16 due to the formation of slim P-E loops, delayed polarization saturation, and ultra-high breakdown field strength (Eb), where the improvement of Eb is attributed to the reduction of porosity and the increase of Eg. Furthermore, the as-fabricated samples also exhibit excellent frequency and temperature stability. This study provides an effective method for developing high-performance dielectric capacitors for energy storage applications.

Remarkable energy storage performance of BiFeO3-based high-entropy lead-free ceramics and multilayers

Electrostatic energy storage capacitors featuring fast charge–discharge capability play an indispensable role in pulsed power capacitors. However, the inverse correlation between polarization and dielectric breakdown strength (Eb) is the main obstacle limiting the access to high recoverable energy storage density (Wrec) and high efficiency (η). In this work, we designed a series of novel (1-x)BiFeO3-x(Ba0.2Sr0.2Ca0.2Bi0.2Na0.2)TiO3 (BF-xBSCBNT, x = 0.4–1.0) high-entropy lead-free relaxor ferroelectric ceramics. The synergy of refined grain size, broadened band gap, and core–shell microstructure is well-investigated by experimental results and phase-field simulations. High polarization difference is achieved by the strengthened relaxation behavior and the dominated polar nanoregions (PNRs). Both high Wrec of 6.0 J/cm3 and η of 81.1 % are achieved in the BF–0.8BSCBNT ceramics. In particular, a remarkable Wrec of 12.1 J/cm3 with a η of 86.1 % are obtained in the multilayer ceramic capacitors (MLCCs) fabricated from the x = 0.8 composition. Excellent temperature stability (<4.0 % in the range of 25–140 °C) and frequency stability (<6.2 % in the range of 1–500 Hz) are also achieved in MLCCs. The excellent energy storage performance demonstrates that high-entropy strategy is effective to develop novel lead-fee ceramics and devices for energy storage applications.

Superior energy storage performance of Sr0.7Bi0.2TiO3-modified Na0.5Bi0.5TiO3-K0.7La0.1NbO3 lead-free ferroelectric ceramics

Na0.5Bi0.5TiO3 (NBT)-based ceramics exhibit significant potential as energy storage dielectric materials due to their high maximum polarization (Pmax). However, their limited energy storage density significantly restricts their practical applications. To address this, this study optimizes the dielectric energy storage characteristics of lead-free relaxor ferroelectric ceramics based on 0.91Na0.5Bi0.5TiO3-0.09 K0.7La0.1NbO3 (NBT-KLN) by incorporating Sr0.7Bi0.2TiO3 (SBT) relaxor additives. The introduction of SBT helps maintain large polarization and induces local disorderly fields, promoting the formation of polar nanoregions. Subsequently, a viscous polymer processing (VPP) technique was employed to reduce defects and enhance density, markedly improving the breakdown strength (BDS). The findings indicate that the BDS of the optimized 0.30SBT (VPP) ceramics increased to 440 kV/cm, while achieving a high energy storage efficiency (η) of 78 % and an elevated energy storage density (Wrec) of 6.29 J/cm3. Additionally, the 0.30SBT (VPP) ceramics demonstrate excellent temperature stability across a broad temperature range from 30 to 120 °C, making them ideal for long-term operation in variable environments. This study demonstrates superior results compared to previous research, thereby opening up new avenues for developing novel lead-free relaxor ferroelectric ceramics with superior energy storage characteristics.

Defect Control of Donor Doping on Dielectric Ceramics to Improve the Colossal Permittivity and Temperature Stability

As the demand for miniaturization of electronic devices increases, ceramics with an ABO3 structure require further improvement of the dielectric constant with high permittivity. In the present work, Ba1−1.5xBixTiO3 (BB100xT, x = 0.0025, 0.005, 0.0075, 0.01) ceramics were prepared via a solid-state reaction process. The effect of Bi doping on dielectric properties of lead-free relaxor ferroelectric BaTiO3-based ceramics was studied. The results showed that both colossal permittivity (37,174) and a temperature stability of TCC ≤ ±15% (−27–141 °C) were achieved in BB100xT ceramics at x = 0.5%. The A-site donor doping produces A-site vacancies, a larger space for Ti4+, and fluctuation of the component, which is partially responsible for the high permittivity and responsible for the temperature stability. Meanwhile, the contribution of defect dipoles, and IBLC and SBLC effects to polarization leads to the colossal permittivity. The formation of a liquid phase during sintering promotes mass transfer when the doping content is higher than 0.5%. This work benefits the exploration of novel multilayer ceramic capacitors with colossal permittivity and temperature stability via defect engineering.

High energy-storage properties of Sr0.7Bi0.2-xLaxTiO3 lead-free relaxor ferroelectric ceramics for pulsed power capacitors

Ceramic capacitors are very promising to be commercialize with ease for high pulse power technology owing to their fast charging/discharging rate, high bending strength and as well as their high energy density. Small, fine, and compacted grains in conjunction with slim P-E loops, and high breakdown electric field strength (Eb) play crucial role in the improvement of recoverable energy storage density. In this work, the microstructure and electrical properties of La2O3 modified Sr0.7Bi0.2-xLaxTiO3 ceramics (SBLTO, x = 0, 0.01, 0.02, and 0.05, and short for SBTO, SBLTO-0.01, SBLTO-0.02, and SBLTO-0.05, respectively) were investigated in details. Furthermore, introducing La2O3 into SBTO ceramics not only refined grains and increased insulation resistance, but also resulted in significantly better energy-storage characteristics, as compared with the pure SBTO ceramics. Recoverable energy-storage density (Wrec) was obtained up to 5.8 J/cm3 in SBLTO-0.01 lead-free ceramic, which is better than that of other reported SBTO-based ceramics. Moreover, the Wrec of the SBLTO-0.01 ceramic also presents good frequency (2–500 Hz) and thermal (25–120 °C) stabilities under an electric field strength of 150 kV/cm. Furthermore, the charge-discharge results demonstrated a high power density∼92 MW/cm3 and a short discharging speed time∼39 ns. As a result, our work offers SBTO-based ceramics with a feasible method for enhancing the energy-storage characteristic.

Achieving high energy-storage density and high temperature and frequency stability in 0.88BT-0.12BMT lead-free relaxor ferroelectric ceramics via NaNbO3 doping

In this work, 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 (x = 0, 0.5, 1, 1.5, 2) ceramics have been synthesized by using the traditional solid-state route. The effects of NaNbO3 on the phase structure, microstructure, dielectric, ferroelectric, and energy storage properties of the 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3 ceramics have been studied in detail. The ceramic doped with 1.5 mol% NaNbO3 exhibited a releasable energy storage density of 2.287 J/cm3, significantly higher than the undoped sample (1.194 J/cm3). The breakdown strength increases from 130 kV/cm for the undoped sample to 210 kV/cm for the sample doped with 1.5mol% NaNbO3. The enhanced breakdown strength of the 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 ceramics is primarily due to NaNbO3 doping, which produces a wider bandgap, smaller grain size, and higher specific resistance. The 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 ceramic's energy storage performance exhibits great temperature stability, frequency stability, and cycle stability at 120 kV/cm.

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Enhanced relaxation behavior and energy storage properties in (Al0.5Nb0.5)4+ complex ions modified Na0.5Bi0.5TiO3-based ceramics under low electric field

In recent decades, high polarization and low residual polarization lead-free relaxor ferroelectric ceramics have attracted lots of focus due to their great potential in dielectric capacitors for energy storage. In this work, Na0.35Bi0.35Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05) lead-free ceramics have been fabricated by the traditional solid-stated reaction method. By doping (Al0.5Nb0.5)4+ complex ions into 0.7Na0.5Bi0.5TiO3-0.3SrTiO3, pure perovskite phases and reduced grain sizes are obtained. Increasing the AN concentration not only moves the Ts toward the lower temperature, but also keeps the permittivity at a high average value, which shows a good thermal stability of the dielectric properties (εr150°C∼3903 ± 15% in the range of 42–232 °C). Furthermore, Na0.35Bi0.35Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 presents a reduced residual polarization due to the improved relaxor behavior, and achieves a moderate energy storage property at low electric field of 155 kV/cm (when x = 0.04, Wrec is 1.85 J/cm3, and η is 89.0%). More importantly, the ceramic also possesses great frequency, temperature and cycle stability. Hence, the (Al0.5Nb0.5)4+ modified 0.7Na0.5Bi0.5TiO3-0.3SrTiO3 ceramics have exhibited a potential application in dielectric capacitors for energy storage.

Achieving High Energy Storage Performance in Lead-Free Relaxor Ferroelectric Ceramics of (1-x)Bi0.88Nd0.10Sm0.02FeO3-xBaTiO3

BiFeO3-based lead-free ferroelectrics have attracted great interest in energy storage applications due to their high spontaneous polarisation strength, however, the high residual polarisation strength (Pr) has become a serious obstacle to their practical application. In this work, (1-x)Bi0.88Nd0.10Sm0.02FeO3-xBaTiO3+0.1 wt% MnO2 ceramics were designed by ion doping and solid solution modification strategies, where Sm3+ and Nd3+ promote ionic disorder and reduce leakage current, and the introduction of nano-BaTiO3 induces the crushing of long-range ferroelectric structure into polar nano-regions with enhanced relaxation. As a result, the ceramic is able to maintain a high maximum polarisation intensity while possessing a low residual polarisation.The recoverable energy density (Wrec) of the 0.50BSNF-0.50BT ceramic is as high as 3.61 J/cm3 with an efficiency of 70.11%. In addition, the 0.50BSNF-0.50BT has good thermal stability (Wrec variation &lt;7%) at 25-120°C. In the charge/discharge test, the Wdis was 2.58 J/cm3 and the discharge time was 273 ns. These results indicate that the 0.50BSNF-0.50BT ceramic is an ideal candidate as a material for energy storage applications.

Enhanced dielectric energy storage performance of Na0.5Bi0.5TiO3-LiTaO3-based lead-free relaxor ferroelectric ceramics through domain structural regulation and improved densification

Ceramic materials with relaxor dielectric properties, expressed as (1-x)(0.94Na0.5Bi0.5TiO3-0.06LiTaO3)-xCaTiO3 [(1-x)(NBT-LT)-xCT] with x values of 0.12, 0.15, 0.18, and 0.21, were synthesized through an A-site doping method to enhance energy storage capabilities. The linear dielectric CaTiO3 was chosen as the acceptor additive, and ceramic samples were prepared using conventional solid-phase and molding techniques. A comprehensive investigation evaluated the influence of different CT concentrations on the phase and energy storage/release characteristics of NBT-LT.Optimal performance was notably achieved with a 15% CT doping concentration, resulting in Wrec and η values of 2.16 J/cm³ and 70%, respectively, for a 100 μm thick sample under a 210 kV/cm voltage. When the film was rolled to a 60 μm thickness, the voltage strength increased to 330 kV/cm, leading to enhanced Wrec (5.33 J/cm³) and η (80%). Within the temperature range of 30 °C to 150 °C, only a marginal change in Wrec (less than 10%) was observed. Frequency conversion tests across the 1 Hz to 100 Hz range demonstrated the material's relative stability, with Wrec exhibiting minimal fluctuations. These findings emphasize the outstanding temperature and frequency stability of the material. During discharge, the material displayed a power density of up to 152 MW/cm³, coupled with a discharge time of 0.3 μs, showcasing remarkable pulse discharge capabilities. The experimental results affirm the promising potential of (NBT-LT)-0.15CT lead-free relaxor ferroelectric ceramics for application in commercial capacitors.

Fulfilling X9R specification in CeO2 modified BNBST-based relaxor ferroelectric energy storage ceramic capacitors

Future low-voltage driven capacitor devices are appealed to employ the eco-friendly ceramics featured with high-stable dielectric energy storage capabilities. Herein, the dielectric energy storage properties of (Bi0·5Na0.5)0.65(Ba0·3Sr0.7)0.35(Ti0·98Ce0.02)O3+8 wt% K0·5Na0·5NbO3+x wt% CeO2 (BNBSTCK + Cx) lead-free relaxor ferroelectric ceramics were comprehensively investigated. By maintaining the relaxor ferroelectric phases near room temperature and disrupting the ferroelectric long-range order via CeO2 additive, the EIA X9R specification was fulfilled at the best composition of x = 8 over a wide range of −74∼208 °C with a relatively high dielectric constant εr = 904 and low loss tanδ = 10−3 (@25 °C & 1 kHz). Meanwhile, the good recoverable energy storage density Wrec = 0.77 J/cm3 and high efficiency η = 91.6% were achieved only at a low electric field of 95 kV/cm. Furthermore, these ceramics exhibited exceptional frequency and cycle dependent energy storage stability, which could guide the design ideas of long-life X9R ceramic capacitors suitable for high and low working temperature environments in low-voltage driven energy storage applications.

The enhancement of energy storage performance of BaTiO3–Bi(Mg0·5Ti0.5)O3 Pb-free ceramics via an optimized viscous polymer process route

In this study, the viscous polymer processing (VPP) technique is implemented to optimize the characteristics of bulk (1-x)BaTiO3-xBi(Mg0·5Ti0.5)O3 (BT-xBMT) lead-free relaxor ferroelectric ceramics, with a focus on enhancing the recoverable energy storage density (Wrec), improving breakdown strength resistance (Eb), and increasing storage efficiency (η). The influence of polyvinyl alcohol (PVA) inclusion in the VPP process on the resulting dielectric ceramics is thoroughly investigated, covering rheological, dielectric, and ferroelectric properties. The results reveal that a gradual increase in PVA quantity during the VPP process effectively improves the density of ceramic blanks. However, an excess of PVA leads to void formation in the ceramic blanks post-debinding, hindering the achievement of a dense structure in the final ceramics and causing performance degradation. The resulting BT-0.405BMT-40 wt% PVA ceramic showed excellent storage performance, with Wrec, η, and Eb of 6.55 J/cm3 81.45 %, and 480 kV/cm, respectively. In comparison to bulk BT-0.405BMT ceramics, there is a notable 2.47-fold increase in Wrec and a 1.92-fold increase in Eb, accompanied by a substantial improvement in η. Moreover, the BT-BMT-40 wt% PVA ceramic exhibits favorable temperature stability (30–150 °C), frequency stability (1–50 Hz), and commendable charge/discharge performance.

Energy storage properties and stability in Nd3+/Ta5+ modified 0.6Na0.5Bi0.5TiO3-0.4Sr0.7Bi0.2TiO3 lead-free relaxor ferroelectric ceramics under a low electric field

Due to the prevalence of wearable electronic devices, Lead-free dielectric ceramics with excellent recoverable energy storage density and efficiency at low electric fields are well worth investigating. Moreover, maintaining excellent energy storage performance (ESP) in different environments is a huge challenge for researchers. In this study, 0.6Na0·5Bi0·5TiO3-0.4Sr0·7Bi0·2TiO3 lead-free relaxor ferroelectric ceramics were modified by (Sr0.7Nd0.2) (Ta0·4Ti0.5)O3 (BNST-xSNTT x = 0, 0.02, 0.04, 0.06). On one hand, BNT has a very high polarization strength, making it a very suitable basic element for designing high energy storage dielectric materials. On the other hand, Sr0·7Bi0·2TiO3 and (Sr0.7Nd0.2) (Ta0·4Ti0.5)O3 were introduced to improve the performance of ceramics, such as inducing polar nanoregions (PNRs), refining grain size, and increasing impedance. The results demonstrate that the energy storage characteristics of BNST-xSNTT were enhanced by introducing SNTT to the BNST. The ceramics exhibited a significant grain size reduction from 0.946 μm (x = 0) to 0.346 μm (x = 0.06). In addition, a great polarization difference (ΔP = 44.29 μC/cm2) was simultaneously achieved in the x = 0.02 sample. As a result, BNST-2SNTT (x = 0.02) ceramic obtained an excellent recoverable energy density of 3.24 J/cm3 and a satisfactory efficiency of 81.4 % at a low electric field of 190 kV/cm. Furthermore, the BNST-2SNTT ceramic exhibits excellent temperature stability (20°C–140 °C), frequency stability (1 Hz–500 Hz), and cycling reliability (10°-106 cycles). The corresponding fluctuation of ESP is less than 5 %. These properties indicate that the BNST-2SNTT ceramic is an excellent dielectric material for energy storage.

Enhanced energy storage properties in BNST-based lead-free relaxor ferroelectric ceramics achieved via a high-entropy strategy

The 0.65(Bi0.5Na0.5)TiO3–0.35SrTiO3-based materials are essential for the development of pulse power capacitors. However, their low recoverable energy storage density and breakdown field strength have hindered further improvement. To address this, a high-entropy strategy based on multiscale regulation is proposed, which involves synergistically manipulating the activation energy and microstructure evolution in BNST-based ceramics through the introduction of Ba(Zr0.2Ti0.2Sn0.2Hf0.2Ta0.2)O3. The inclusion of high-insulating oxides can significantly raise the activation energy of the entire system. Furthermore, the high-entropy material can significantly increase the atomic disorder and lattice distortion, resulting in strong local polar fluctuations on several nanoscales and excellent energy storage characteristics. As a result, this approach yields an impressive Wrec of ∼ 4.89 J/cm3 and a high efficiency of ∼92.1 % at 351 kV/cm, and the outstanding thermal endurance (20∼150 °C), frequency stability (5∼1000 Hz) and fatigue (100∼105 cycles). This study provides an effective strategy for achieving excellent comprehensive performances in high-entropy ceramics.

BaTiO3-based lead-free relaxor ferroelectric ceramics for high energy storage

Barium titanate (BaTiO3, BT) is widely used in capacitors because of its excellent dielectric properties. However, owing to its high remanent polarisation (Pr) and low dielectric breakdown field strength (Eb), achievement of high energy storage performance is challenging. Herein, a systematic strategy was proposed to reduce Pr and elevate Eb of BT via: (i) modification of the relaxor behavior by alloying it with Bi(Mg2/3Ta1/3)O3 (BMT) and (ii) heightening Eb by introducing NaTaO3 (NT) with high band gap. Consequently, the energy storage efficiency (η) of 90 % and high Eb of 780 kV cm−1 were achieved simultaneously for the BT-BMT-xNT system, which facilitated the recoverable energy density (Wrec) of 6.02 J cm−3. At 300 kV cm−1, its temperature (20–120 °C) and frequency (1–500 Hz) stabilities were found to be good. Moreover, the BT-BMT-0.15NT possessed ultrafast discharge rate (t0.9 < 51 ns) and ultrahigh power density (PD > 94 MW cm−3). This study offers an effective strategy for the design of novel high-performance dielectric energy storage materials.

Temperature stability lock of high-performance lead-free relaxor ferroelectric ceramics

Lead-free dielectric ceramics are considered a highly promising material for pulse power capacitors due to their excellent energy storage performance. However, it is challenging to achieve high-temperature energy storage performance of dielectric ceramics to meet the needs of practical applications. Here, an effective strategy for constructing temperature stability lock is designed to regulate the phase composition and temperature stability based on the polymorphic polarization structure. By realizing the ergodic-state-dominated metastable relaxation structure, high energy storage performance and temperature-insensitive structure can be achieved in relaxor ferroelectric ceramics. Taking the Bi0.5Na0.5TiO3-based solid solution as an example, we demonstrate the metastable relaxation structure induced by the proportion of phase composition. This leads to a large recoverable energy density (Wrec) of 10.7 J cm−3 and a high efficiency (η) of 91 %. Together with the good thermal stability of Wrec (7.1 ± 0.1 J cm−3) and η (86 ± 5 %) values at 500 kV cm−1 in the temperature range from 20 °C to 200 °C, outperforming all reported Bi0.5Na0.5TiO3-based energy storage ceramics. Our work provides a method for obtaining lead-free dielectric ceramics with high-temperature energy storage performance through temperature stability lock.

Enhancement of energy storage performances in BaTiO3-based ceramics via introducing Bi(Mg2/3Sb1/3)O3

Lead-free relaxor ferroelectric ceramics have attracted extensive attention on account of their excellent energy storage properties. However, these ceramics still have some difficulties in improving the energy storage density, efficiency and stability. Herein, (1-x)BaTiO3-xBi(Mg2/3Sb1/3)O3 (BT-xBMS, x = 0.08, 0.12, 0.16, and 0.20) ceramics were designed in this study. After the addition of Bi/Mg/Sb (BMS) elements into BaTiO3(BT) system, the grain size of ceramics increases obviously. And the grain boundary activation energy increases with the increase of resistivity, which is due to the difficulty of grain boundary oxygen vacancy transition. This measure can effectively enhances the breakdown strength (Eb), thereby improving the energy storage properties. Significantly, it is worth mentioning that BT-0.16BMS ceramics exhibit excellent total energy density (Wtotal = 4.56 J/cm3), large recyclable energy storage density (Wrec = 4.28 J/cm3) and high efficiency (η = 93.70 %) under Eb of 550 kV/cm. In particular, BT-0.16BMS ceramics achieved excellent current density (CD = 1475.58 A/cm2), power density (PD = 177.07 MW/cm3), discharge energy density (Wd = 1.35 J/cm3) and extremely fast discharge time (t0.9 = 27.34 ns). In addition, BT-0.16BMS ceramics have excellent temperature range (20–140 °C) and frequency (1–200 Hz) stability. Therefore, the excellent energy storage properties make BT-0.16BMS ceramics have broad prospects in advanced pulse power capacitors.