Lead-free Dielectric Ceramics Research Articles

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.

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.

Enhancing energy storage efficiency in lead-free dielectric ceramics through relaxor and lattice strain engineering

Dielectric capacitors with high power density and fast charge-discharge speed play an essential role in the development of pulsed power systems. The increased demands for miniaturization and practicality of pulsed power equipment also necessitate the development of dielectric materials that possess high energy density while maintaining ultrahigh efficiency (η). In particular, ultrahigh efficiency signifies minimal energy loss, which is essential for practical applications but challenging to effectively mitigate. Here, we demonstrate a strategy of incorporating heterovalent elements into Ba(Zr0·1Ti0.9)O3, which contributes to achieving relaxor ferroelectric ceramics and reducing lattice strain, thereby improving the comprehensive energy storage performance. Finally, optimal energy storage performance is attained in 0.85Ba(Zr0·1Ti0.9)O3-0.15Bi(Zn2/3Ta1/3)O3 (BZT-0.15BiZnTa), with an ultrahigh η of 97.37% at 440 kV/cm (an advanced level in the lead-free ceramics) and an excellent recoverable energy storage density (Wrec) of 3.74 J/cm3. Notably, the BZT-0.15BiZnTa ceramics also exhibit exceptional temperature stability, maintaining fluctuations in Wrec within ∼10% and η consistently exceeding 90% across the wide temperature range of −55 °C to160 °C, and under a high electric field of 250 kV/cm. All these features demonstrate that the relaxor and lattice strain engineering strategies have been successful in achieving high-performance lead-free ceramics, paving the way for designing high-efficiency dielectric capacitors with a wide temperature range.

Broad-high operating temperature range and enhanced energy storage performances in lead-free ferroelectrics

The immense potential of lead-free dielectric capacitors in advanced electronic components and cutting-edge pulsed power systems has driven enormous investigations and evolutions heretofore. One of the significant challenges in lead-free dielectric ceramics for energy-storage applications is to optimize their comprehensive characteristics synergistically. Herein, guided by phase-field simulations along with rational composition-structure design, we conceive and fabricate lead-free Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-Sr(Sc0.5Nb0.5)O3 ternary solid-solution ceramics to establish an equitable system considering energy-storage performance, working temperature performance, and structural evolution. A giant Wrec of 9.22 J cm−3 and an ultra-high ƞ ~ 96.3% are realized in the BNKT-20SSN ceramic by the adopted repeated rolling processing method. The state-of-the-art temperature (Wrec ≈ 8.46 ± 0.35 J cm−3, ƞ ≈ 96.4 ± 1.4%, 25–160 °C) and frequency stability performances at 500 kV cm−1 are simultaneously achieved. This work demonstrates remarkable advances in the overall energy storage performance of lead-free bulk ceramics and inspires further attempts to achieve high-temperature energy storage properties.

Improving energy storage performance and high-temperature stability in Bi0.5Na0.5TiO3-based lead-free dielectric ceramics by ZrO2 doping

The effects of ZrO2 addition on the microstructure, dielectric properties, and energy storage performance of Bi0.5Na0.5TiO3–Bi0.5K0·5TiO3–BaTiO3–Sr(Mg1/3Nb2/3)O3 (BBNKT-SMN) ceramics were systematically investigated. The XRD results show that ZrO2 dissolved in the perovskite matrix without any detectable secondary phases. ZrO2 doping can improve densification, grain growth, and energy storage performance. The sample doped with 4 mol% ZrO2 exhibited excellent dielectric thermal stability, meeting the Z9R specification and having potential applications in high-temperature capacitors. Finally, an optimal recoverable energy storage density Wrec = 3.0 J/cm3 at 260 kV/cm and a high energy storage efficiency η = 88.2% were achieved. In addition, this ceramic exhibited excellent thermal stability (30–180 °C), frequency insensitivity (1–100 Hz), and high-cycle stability (up to 104). This study further demonstrates that the addition of ZrO2 is a simple and effective way for improving the thermal stability of the dielectric and the energy storage performance.

Markedly improved energy-storage performance of Na0.5Bi0.5TiO3-based ferroelectric ceramics through introducing Ba(Mg1/3Ta2/3)O3 non-polar phase

Eco-friendly dielectric energy-storage ceramics capacitors are extremely urgent for pulsed power system applications. Unfortunately, it is a grand challenge to boost the energy-storage properties. In this study, we make use of a composition driven strategy to refine microstructures, enhance dielectric relaxation, and adjust phases composition of (1-x) (Na0.47Bi0.47Ba0.06)TiO3-xBa(Mg1/3Ta2/3)O3 lead-free ceramics. The results showed that all the sintered samples owned a perovskite structure, and dense microstructure. Furthermore, with Ba(Mg1/3Ta2/3)O3 doping level increasing, the peak of εr shifts to a lower temperature, and becomes boarder. Interestingly, the superior recoverable energy density (Wrec)⁓5.9 J/cm3 and energy efficiency (η)⁓82.3% values are simultaneously received for the x = 0.14 ceramic, respectively. Moreover, the above sample also illustrates positive temperature (25–120 °C) and frequency (1–500 Hz) energy-storage stabilities. Meanwhile, a power density of 59.2 MW/cm3, as well as a discharge speed time of 199 ns are also obtained in the x = 0.14 ceramic. It is believed that this work will give a helpful guideline for the promotion of Na0.5Bi0.5TiO3 lead-free dielectric ceramics capacitors.

Synergistic effect of multi-phase and multi-domain structures induced high energy storage performances under low electric fields in Na0.5Bi0.5TiO3-based lead-free ceramics

Lead-free dielectric ceramics with ultrahigh-power density, fatigue properties, and excellent thermal stability are regarded as potential dielectric energy storage materials for the next-generation advanced pulse power capacitors. However, the large energy storage density (Wrec) and high discharging efficiency (η) of dielectric capacitors are generally achieved under ultrahigh electric fields. Developing dielectric capacitors with high energy storage performances under low electric fields is of great significance. Herein, we utilized a synergistic design strategy of multi-phase and multi-domain structures to successfully synthesize the (0.65-x)(Na0.5Bi0.5)TiO3-0.35(Sr0.7Bi0.2)TiO3-xAg0.97Nd0.01Ta0.2Nb0.8O3 ((0.65-x)BNT-0.35SBT-xANTN) ceramics suitable for the low electric field situation. The formed multi-phase coexistence structure of the Rhombohedral (R3c) and Tetragonal (P4bm) phases and the elevated concentration of Bi3+ at A site in BNT-SBT-ANTN ceramics are beneficial to obtain the high maximum polarization (Pmax). Meanwhile, the introduction of ANTN in the BNT-SBT matrix can disrupt the long-range order ferroelectric domain structures and also form the local polar nanoregions (PNRs), leading to the small remnant polarization (Pr) and the improvement of the relaxation behavior. Encouragingly, the optimized 0.63BNT-0.35SBT-0.02ANTN composition exhibits excellent energy storage performances with a large Wrec of 3.61 J/cm3 and relatively high η of 80.6% at a low electric field of 200 kV/cm. In addition, this 0.63BNT-0.35SBT-0.02ANTN sample presents better thermal stability (20–120 ℃) and frequency stability (10–1000 Hz). Moreover, the high charge power density (PD) of 69.42 MW/cm3, the rapid discharge speed rate (τ0.9) of 0.22 μs, and the good fatigue endurance are also achieved in the 0.63BNT-0.35SBT-0.02ANTN sample. This work may provide an effective method for designing dielectric ceramics with remarkable comprehensive energy storage performances at low electric fields to meet the requirements of advanced energy storage capacitors under extreme conditions.

Excellent Energy-Storage Performance in Lead-Free Capacitors with Highly Dynamic Polarization Heterogeneous Nanoregions.

Lead-free dielectric ceramics with excellent energy-storage performance are crucial to the development of the next-generation advanced pulse power capacitors. However, low energy-storage density limits the evolution of capacitors toward lightweight, miniaturization, and integration. Here, an effective strategy of constructing highly dynamic polarization heterogeneous nanoregions is proposed in lead-free relaxors to realize an ultrahigh energy-storage density of ≈8.0 J cm-3 , making almost ten times the growth of energy-storage density compared with pure Bi0.5 Na0.5 TiO3 ceramic, accompanied by a higher energy efficiency of ≈80% as well as an ultrafast discharge rate of ≈20ns. Ultrasmall polarization heterogeneous nanoregions with different orientations and ultrahigh flexibility, and significantly decreased grain size to submicron lead to reduced heat loss, improved breakdown electric field and polarization, enhanced relaxation, and delayed polarization saturation behaviors, contributing to the remarkable energy-storage performance. Moreover, the breakdown path distribution or electrical tree evolution behaviors are systematically studied to reveal the origin of ultrahigh breakdown electric field through phase field simulations. This work demonstrates that constructing highly dynamic polarization heterogeneous nanoregions is a powerful approach to develop new lead-free dielectric materials with high energy-storage performance.

Lead-free KNN-based ceramics incorporated with Bi(Zn2/3Nb1/3)O3 possessing excellent optical transmittance and superior energy storage density

The application of lead-free dielectric ceramics for energy storage has received extensive attention because of their remarkable potential as pulse capacitors in power electronic devices. The current study developed a strategy for improving the energy storage performance of (K0.5Na0.5)NbO3 (KNN)-based ceramics by incorporating Bi(Zn2/3Nb1/3)O3 to reduce grain size, increase dielectric breakdown strength, and enhance ferroelectric relaxation degree. The resulting 0.87KNN–0.13BZN ceramics exhibited a high energy density (7.4 J/cm3) and moderate energy efficiency (74%) at an ultrahigh electric field (750 kV/cm) as well as excellent optical properties. Therefore, the 0.87KNN–0.13BZN ceramic is a promising candidate for pulse capacitors, providing a feasible approach for the development of new lead-free energy storage materials.

Enhanced breakdown strength and excellent energy storage stability by B site hetero-valent doping in Sr0.7Bi0.2TiO3-based lead-free ceramic

Environment-friendly energy storage materials are embraced in global researches. Aiming at improving the energy storage performances of lead-free dielectric ceramics, the Sr0.7Bi0.2Ti(1–1.25x)NbxO3 (SBT-xN, x = 0 ∼ 0.125) lead-free ceramics were synthesized via the conventional solid state method in this work. Outstanding total energy storage density (Wtotal = 3.998 J/cm3), recoverable energy storage (Wrec = 3.43 J/cm3), and high energy storage efficiency (η of 85.84%) were obtained when x = 0.075 under the electric field of 385 kV/cm. Meanwhile, a satisfied temperature (30 ℃−110 ℃ variation less than 14%), frequency stability (10–400 Hz variation less than 1%), and anti-fatigue characteristic (107 cycles variation less than 1%) were achieved. Furthermore, the sample exhibited a remarkable discharge energy density (Wd = 3.885 J/cm3), ultrafast discharge speed (t0.9 = 73 ns), and giant discharge power density (Pd = 327.01 MW/cm3) at 400 kV/cm in charge-discharge tests. Great temperature stability (30 ℃−150 ℃ variation less than 8%) and pulse repetition frequency discharge stability (2×105 times variation less than 3.5%) were also obtained. The excellent characteristics suggest that the ceramic is a prospective candidate for advanced pulse power equipment.

Ultrahigh energy density and excellent discharge properties in Ce4+ and Ta5+ co-modified AgNbO3 relaxor antiferroelectric ceramics via multiple design strategies

Silver niobate (AgNbO3) has been recently regarded as one of the best candidates for developing high-performance dielectric capacitors on account of its large maximum polarization and near-zero remnant polarization, but its room-temperature ferrielectric (FIE) behavior and large electric hysteresis impede further improvement of energy storage properties. In order to solve this issue, herein, we design Ce4+ and Ta5+ co-modified (Ag0.96Ce0.01)(Nb1-xTax)O3 relaxor antiferroelectric (AFE) ceramics. The introduction of Ce4+ and Ta5+ decreases the tolerance factor, reduces the B-site cation polarizability, and enhances A- and B- site cation disorder, leading to suppressed FIE characteristic, improved AFE stability, and enhanced relaxor degree. Besides, the co-doping strategy causes the decrease of the grain size, and the experimental results and finite element simulations both indicate that this is fairly effect on the improvement of the breakdown strength. Consequently, an ultrahigh recoverable energy density of 7.37 J/cm3, which far exceeds those of the latest AgNbO3-based ceramics, and a large efficiency of 75.66% are simultaneously achieved in (Ag0.96Ce0.01)(Nb0.7Ta0.3)O3 ceramics. More encouragingly, the ceramic exhibits excellent actual discharge capacity with ultrafast discharge time of 23 ns and ultrahigh power density of 294.28 MW/cm3, which outperforms many recently reported lead-free dielectric ceramics, and the discharge properties are fairly stable during a wide temperature range of 20–180 °C. This work sheds light on designing and developing high-performance lead-free dielectric capacitors applicable in harsh environment.

Preparation and dielectric properties of lead-free perovskite-structured high-entropy ceramics of (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Me0.5)O3-δ (Me=Sn, Zr, Hf) via doping at both A and B sites

A series of lead-free perovskite-structured high-entropy dielectric ceramics with a composition of (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Me0.5)O3 (Me = Sn, Zr, Hf) were designed by doping at both the A and B sites. Specifically, these ceramics were prepared via a solid-state reaction method combined with conventional sintering at 1500 °C for 10 h. All high-entropy ceramics were consisted of a perovskite-structured single solid solution with an average grain size of 2.78–3.85 μm. Of the three samples, (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Sn0.5)O3 exhibited the highest dielectric constant, which remained stable from in 25–312 °C. All three groups of high-entropy ceramics showed typical relaxor behaviour. The discharge energy density (Wd = 0.31 J/cm3), energy storage efficiency (η = 90.88%) and breakdown strength (BDS = 300 kV/cm) of (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Sn0.5)O3 were much higher than those of BaTiO3 (Wd = 0.08 J/cm3, η = 46.09%, BDS = 30 kV/cm) and other reported lead-free dielectric ceramics. These results demonstrate that high-entropy (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Me0.5)O3 ceramics are promising new candidates for high-performance, lead-free dielectric ceramics.

Energy storage performance of NaNbO3 lead-free dielectric ceramics by doping Sr(Mg1/3Sb2/3)O3

Energy storage performance in NaNbO3 lead–free dielectric ceramics by doping Sr(Mg1/3Sb2/3)O3.

Realizing ultrahigh breakdown strength and ultrafast discharge speed in novel barium titanate-based ceramics through multicomponent compounding strategy

Lead-free dielectric ceramics have been an important segment in the energy storage field. In this work, a synergistic optimization strategy of multicomponent compounding involving 0.9[0.88Ba1-xCaxTiO3-0.12Bi(Mg2/3(Nb0.85Ta0.15)1/3)O3]− 0.1Bi0.5Na0.5TiO3 (B1-xCxT-BMNT-BNT) ceramics were proposed. With the increase of Ca2+ content (x), the content of the CaTiO3 phase increases, which obviously enhances the breakdown strength (BDS) and energy storage properties. The optimal energy storage performances were obtained in the B0.6C0.4T-BMNT-BNT ceramic, showing a large recoverable energy density (Wrec) of 3.59 J/cm3 and ultrahigh efficiency (η) of 90.86% at 430 kV/cm. Meanwhile, the B0.6C0.4T-BMNT-BNT material also exhibits good temperature stability (20–180°C), frequency stability (1–500 Hz) and fatigue resistant (1–105 cycles). In addition, the B0.6C0.4T-BMNT-BNT ceramic also possesses ultrafast discharge time (t0.9 = 38.6 ns) in the charge and discharge test. The above merits make the B0.6C0.4T-BMNT-BNT ceramic a promising candidate for wide-temperature dielectric capacitors in pulse power applications.

0.74NaNbO3–0.26Sr(Mg1/3Nb2/3)O3 lead-free dielectric ceramics with high energy storage properties

Sodium niobate (NaNbO3) ceramics are commonly investigated for use as energy storage ceramics because of their excellent properties. NaNbO3 ceramics are modified mainly by doping with a Bi-based composite perovskite, that is, by the nonequivalent doping of Bi3+ at the A site of the NaNbO3 ceramic. In addition, the high volatility of Bi at high temperatures increases the defects in the ceramics. This paper provides a new idea of doping modification of sodium NaNbO3-based energy storage ceramics. Here, (1−x)NaNbO3–xSr(Mg1/3Nb2/3)O3 (x = 0.17, 0.20, 0.23, 0.26) ceramics were prepared by doping NaNbO3 with an Sr-based composite perovskite. Compared with Bi-based composite perovskite, Sr-based composite perovskite doping of NaNbO3 ceramics can also obtained good energy storage properties: a total energy storage density of 4.28 J/cm3 and an energy storage efficiency of 89.3%. In addition, the ceramics exhibited good frequency stability (2–200 Hz) and a high charge/discharge rate (1.06 μs).

Realizing simultaneously excellent energy storage and discharge properties in AgNbO3 based antiferroelectric ceramics via La3+ and Ta5+ co-substitution strategy

AgNbO3 based antiferroelectric (AFE) ceramics have large maximum polarization and low remanent polarization, and thus are important candidates for fabricating dielectric capacitors. However, their energy storage performances have been still large difference with those of lead-based AFEs because of their room-temperature ferrielectric (FIE) behavior. In this study, novel La3+ and Ta5+ co-substituted AgNbO3 ceramics are designed and developed. The introduction of La3+ and Ta5+ decreases the tolerance factor, reduces the polarizability of B-site cations and increases local structure heterogeneity of AgNbO3, which enhance AFE phase stability and refine polarization-electric field (P–E) loops. Besides, adding La3+ and Ta5+ into AgNbO3 ceramics causes the decrease of the grain sizes and the increase of the band gap, which contribute to increased Eb. As a consequence, a high recoverable energy density of 6.79 J/cm3 and large efficiency of 82.1%, which exceed those of many recently reported AgNbO3 based ceramics in terms of overall energy storage properties, are obtained in (Ag0.88La0.04)(Nb0.96Ta0.04)O3 ceramics. Furthermore, the discharge properties of the ceramic with discharge time of 16 ns and power density of 145.03 MW/cm3 outperform those of many lead-free dielectric ceramics.

Local Diverse Polarization Optimized Comprehensive Energy-Storage Performance in Lead-Free Superparaelectrics.

Lead-free dielectric ceramics with ultrahigh energy-storage performance are the core components used in next-generation advanced pulse power capacitors. However, the low energy storage density largely hinders their development towards miniaturization, lightweight, and integration. Here, an effective strategy of constructing local diverse polarization is designed in superparaelectrics to realize an ultrahigh energy storage density of ≈10.59 J cm-3 as well as a large efficiency of ≈87.6%. The excellent comprehensive energy-storage performance is mainly attributed to the design of ultrasmall polar nanoregions with local diverse polarization configuration, confirmed by scanning transmission electron microscopy, leading to the reduced heat loss, substantially enhanced polarization, and breakdown electric field compared to ceramics with single polarization configuration. Benefiting from these features, outstanding temperature/frequency/cycling stability and superior charge/discharge performance (power density ≈187.5 MW cm-3 , discharge energy density ≈3.52 J cm-3 , discharge rate ≈77ns) are also achieved. This work demonstrates that local diverse polarization is a super strategy to design new dielectric materials with high energy-storage performance.

Medium electric field-induced ultrahigh polarization response and boosted energy-storage characteristics in BNT-based relaxor ferroelectric polycrystalline ceramics

Lead-free dielectric ceramics with a high recoverable energy-storage density (Wrec) and improved efficiency (η) are crucial for the development of pulse power capacitor devices. Although Wrec has been constantly improving, mainly via an increased breakdown electric field strength (Eb), a large driving electric field (>500 kV/cm) increases security risks and consequently increases insulating technology costs. In this work, we present a new (Bi0.5Na0.5)TiO3 (BNT)-based relaxor ferroelectric system, (1−x)(0.75Bi0.5Na0.4K0.1TiO3-0.25SrTiO3)-xBi(Mg0.5Ti0.5)O3 (BS-xBMT), with x ranging from 0.05 to 0.20. BMT disrupts both the A- and B-site long-range ferroelectric order of the ABO3 perovskite-structured BS matrix, induces polar nanoregions, and simultaneously increases Wrec and η. Aided by the viscous polymer process, the Eb with x = 0.15 increased to 270 kV/cm, and a maximum polarization (Pm) of 62 μC/cm2 was attained. A boosted Wrec of 4.82 J/cm3 and a high η of 84.9% were simultaneously obtained, together with good temperature stability from 30 to 140 °C. These results show that BNT-based dielectric ceramics with superior energy-storage properties can be obtained under a medium electric field.

Enhanced energy storage properties under low electric fields in (Bi0.5Na0.5)TiO3-based relaxor ferroelectrics via a synergistic optimization strategy

Lead-free dielectric ceramics with high energy storage performance (ESP) are strongly desired for pulse power capacitor applications. However, low recoverable energy storage density (Wrec) under low electric fields seriously hinders their applications in miniatured and integrated electronic devices. In this work, we adopted a synergism strategy to develop (Bi0.5Na0.5)0.7Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 (BNST-xAN) ceramics with substantially enhanced low-field ESP through combining composition design and tape-casting approaches. Complex-ion substitution of (Al0.5Nb0.5)4+ for Ti4+ shifted the temperature of maximum dielectric constant towards room temperature direction, made relaxor behavior stronger and promoted formation of highly dynamic nanodomains, thus reducing the remanent polarization. Besides, refined submicron grains and improved densification behavior were achieved in those ceramics fabricated by tape casting, further increasing the breakdown strength. Consequently, a large Wrec of 4.30 J/cm3 was achieved at a low electric field of 230 kV/cm at x = 0.10, which is superior to previously reported lead-free energy storage ceramics under low electric fields. Moreover, our ceramics exhibited brilliant thermal endurance (20–140 °C) and frequency stability (0.2–200 Hz) together with fast discharge speed. These characteristics suggest the great potential of the BNST-0.10AN ceramic for low-field and high-performance energy storage capacitor applications.

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.