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Tetragonal tungsten bronze structure (TTB) compounds have attracted tremendous interest for their applications in energy storage, especially as dielectric capacitor mediums. However, constrained by the inverse correlation of polarization and electric breakdown field in relaxor ferroelectrics, there is still a major challenge in improving energy density. To addresse this challenge, a viable strategy of constructing relaxor behavior with robust electrical insulation in TTB-type Sr 0.485 Ba 0.47 Gd 0.03 Nb 2- x Zr x O 6 (SBN-Gd-Zr x) by introducing ZrO 2 during the preparation process was proposed. By introducing Zr4+ in the B-site, we have revealed how Zr4+ affects the dielectric and ferroelectric characteristics to explore the intrinsic relaxation. Based on the analysis of Rietveld refinement against synchrotron X-ray powder diffraction and Raman results, the substitution of Gd3+ and Zr4+ for Sr2+ and Nb5+ in Sr 0.53 Ba 0.47 Nb 2 O 6 caused a decline in tetragonality and a shrinkage of the unit cell due to the lattice defect of [Gd Sr ]• and [Zr Nb ] ' , which mutually compensates effectively alleviate the distortion of BO 6 and then favors the balance of polarization and dielectric constant. The accrual of additional ZrO 2 at grain boundaries significantly enhances electrical insulation characteristics, as validated by complex impedance spectroscopy. At near room temperature, all Zr-doped SBN-Gd compounds of the series exhibit heightened relaxation and undergo a phase transition from ferroelectric to paraelectric. As a result, in tandem with the synchronous augmentation in breakdown electric field (E B) and saturation polarization (P m), optimal energy storage characteristic is realized in the SBN-Gd-Zr0.2 sample. It attains a remarkable W rec of 2.67 J/cm3 and an efficiency ƞ of 91.21 %, showcasing excellent suitability in terms of different frequencies and temperatures, which far exceeds that of Gd-modified SBN ceramics and pure SBN ceramics. These results exemplify an efficacious strategy for designing novel TTB dielectrics by coupling relaxor modulation with electrical insulation, and position them competitively for implementation in dielectric storage capacitors utilized in pulsed power devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • 0.9NBST-0.1BMS lead-free ceramics with W rec = 6.68 J/cm3 and η = 89.1 % were designed and fabricated. • Small grain size and high activation energy of grain boundary leads to high breakdown field (405 kV/cm). • The energy storage potential (W rec /E b) is up to 0.01649 μC/cm2. • Excellent fatigue endurance over 105 electrical cycles (the W rec variation is less than 1.5%). Ferroelectric ceramics, as a potential candidate for high-power energy storage capacitors, lies in their excellent recoverable energy storage density (W rec) and outstanding efficiency (η) in practical applications. Herein, a new type of lead-free ceramics (1- x)(Na 0.5 Bi 0.5) 0.65 Sr 0.35 TiO 3 - x BiMg 0.5 Sn 0.5 O 3 or (1- x)NBST- x BMS was prepared with the aim of enhancing the breakdown strength (E b) and reducing the energy storage loss through grain refinement. It was found that E b of 0.9NBST-0.1BMS reaches 405 kV/cm due to the reduction in the grain size of ceramic and thus the extremely high ratio of grain boundary resistance to grain resistance. Besides, a remarkable energy-storage performance was obtained, that is, W rec and η are ∼ 6.68 J/cm3 and 89.1% at 405 kV/cm, respectively, along with excellent stability in terms of frequency, temperature, and fatigue endurance. The outstanding energy-storage performance is resulted from modulating the grain size via doping the moderate content of Bi3+ and Mg2+/Sn4+, which is beneficial to increase the breakdown field by increasing resistivity under high electric field while increasing the grain boundary activation energy and promote the formation of a relaxor state at the same time. More importantly, energy storage potential (defined as W rec /E b) is up to 0.01649 μC/cm2, being the highest value reported so far for BNT-based ceramics in energy-storage application. Our results pave the way for practical applications of NBST-based ferroelectric capacitors with excellent energy storage performance. [ABSTRACT FROM AUTHOR]

• Through modifying Sn4+ content, the breakdown strength is increased by 112.3%. • The recoverable energy density enhanced by 276.2% via incorporation of Sn4+. • The doping of Sn4+ inhibits the migration of grain boundary and refines grains. • The delayed polarization saturation result from Sn4+ with d10 substitutes Ti4+ with d0. [Display omitted] High-performance dielectric ceramic capacitors is a promising candidate in energy storage devices. In this work, the energy storage performance of Ba 0.94 Ca 0.06 Ti 1−x Sn x O 3 (x = 0.04, 0.08, 0.12, 0.16) ceramics was systematically studied. Through modifying Sn4+ doping content, the breakdown strength of the ceramics is enhanced by 112.3% from 133.4 kV/cm (Ba 0.94 Ca 0.06 Ti 0.96 Sn 0.04 O 3) to 283.2 kV/cm (Ba 0.94 Ca 0.06 Ti 0.84 Sn 0.16 O 3). Accordingly, the recoverable energy density is greatly increased by 276.2%, that is, from 0.42 J/cm3 grow to 1.58 J/cm3. The enhanced energy storage properties could be ascribed to the following aspects: (1) the doping of Sn4+ with a larger ionic radius inhibits the migration of grain boundaries and therefore refines grains, resulting in a higher activation energy and a larger E b ; (2) the long range polar order is broke and polar nano-regions are formed, giving rise to lower energy barrier and smaller P r ; (3) the weakened ferroelectricity and delayed polarization saturation lead to higher W rec owing to the fact that Sn4+ with d10 electronic configurations substitutes Ti4+ with d0. Our work provides a novel approach for enhancing energy storage performance in dielectric ceramic capacitors. [ABSTRACT FROM AUTHOR]

• Tailoring the first-order O-T phase transition strategy was adopted in this work. • The large Δ T of 0.3 K is attained in 0.6BST-0.4BZT ceramic at room temperature. • The Δ T of 0.53 K is achieved at 342 K due to the quadruple point coexistence. The development of refrigeration technology has burgeoned in response to the challenges posed by global warming. Notably, electrocaloric materials have garnered significant attention for their potential in miniaturization and high efficiency. However, investigations into the electrocaloric response in proximity to orthorhombic-tetragonal phase transition in BaTiO 3 -based ferroelectric ceramics remain scarce. In this study, we employ a lead-free x (Ba 0.7 Sr 0.3)TiO 3 -(1- x)Ba(Zr 0.2 Ti 0.8)O 3 polycrystalline ceramics fabricated through the solid-state reaction method. The comprehensive analysis includes elucidation of the phase structure, surface morphologies, dielectric properties, domain switching behavior, and the electrocaloric effect. Integrating these findings with the phase diagram unveils optimal adiabatic temperature change (Δ T) achieved within the quadruple point coexistence region. That is, the highest Δ T of 0.53 K is achieved for x = 0.4 ceramic, which is attributed to the increased entropy resulting from multiple polar phases. Remarkably, the highest Δ T of 0.3 K is attained in x = 0.6 ceramic under a low driving electric field of 30 kV/cm at room temperature, precisely within the orthorhombic-tetragonal transition temperature. The investigation underscores the efficacy of regulating the first-order orthorhombic-tetragonal phase transition to achieve exceptional electrocaloric responses at room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of ST and BMH doping in BNT on energy storage properties were studied. • By modifying composition, good energy storage properties are obtained in BNST-BMH. • Ultrahigh W rec of 5.59 J/cm3 and η of 85.3% are realized in BNST-BMH ceramic. • BNST-BMH ceramic exhibits excellent thermal stability from 20 °C to 140 °C. • A superior fatigue resistance over 105 cycles was achieved in BNST-BMH ceramic. Dielectric ceramic capacitors with high energy density are one of the great bright energy storage devices. Here, the Bi 0.5 Na 0.5 TiO 3 , 0.75Bi 0.5 Na 0.5 TiO 3 -0.25SrTiO 3 , 0.65Bi 0.5 Na 0.5 TiO 3 -0.35SrTiO 3 and 0.88(0.65Bi 0.5 Na 0.5 TiO 3 -0.35SrTiO 3)-0.12Bi(Mg 0.5 Hf 0.5)O 3 , (abbreviated as BNT, BNT-25ST, BNT-35ST and BNST-BMH, respectively) ceramics were produced by solid state sintering method. The influence of solid solution of SrTiO 3 and Bi(Mg 0.5 Hf 0.5)O 3 doping in Bi 0.5 Na 0.5 TiO 3 on crystal structure, microstructure, electrical and energy storage performance were evaluated systematically. By optimizing ceramics composition, high breakdown field and slim hysteresis loops were simultaneously realized due to enhanced band gap, refined grain size and nano-domains formed, which can be verified by the transmission electron microscope (TEM), piezoelectric force microscope (PFM) and ultraviolet–visible spectrum. Therefore, an ultrahigh recoverable energy density of 5.59 J/cm3 with brilliant efficiency of 85.3% is realized in BNST-BMH ceramic. Besides, the BNST-BMH also exhibits prominent temperature stability at 20–140 °C, superior fatigue resistance beyond 105 cycles and outstanding frequency stability at 1–200 Hz. Our work offers a novel way for designing dielectric capacitors and also proves that BNST-BMH is indeed a great hopeful dielectric energy storage material in pulse power electronics. [ABSTRACT FROM AUTHOR]

The 0.65(Bi 0.5 Na 0.5)TiO 3 –0.35SrTiO 3 -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(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 Ta 0.2)O 3. 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 W rec 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. [Display omitted] [ABSTRACT FROM AUTHOR]

The urgent requirement of environment-friendly materials with excellent energy storage performance for pulse power systems has sparked considerable research on lead-free ceramics. In this work, a new lead-free 0.90(0.80NaNbO3–0.20Sr0.7Bi0.2TiO3)–0.10BaSnO3 ceramic with high recoverable energy storage density (Wr = 3.51 J/cm3) and decent energy storage efficiency (η = 70.85%) has been obtained. In particular, these ceramics exhibit an ultrahigh breakdown strength of 402 kV/cm due to the dense microstructure and small grain size. The impedance analysis also reveals that the incorporation of BaSnO3 is conducive to the enhancement of insulation ability and breakdown strength. Additionally, great thermal stability (ΔWr < 10% over 20–120 °C at 200 kV/cm) and fatigue resistance (ΔWr < 1% after 120,000 electrical cycles at 200 kV/cm) are observed, indicating that the 0.90(0.80NaNbO3–0.20Sr0.7Bi0.2TiO3)–0.10BaSnO3 ceramics have promising application prospect for high-temperature energy storage devices in pulse power applications. [ABSTRACT FROM AUTHOR]

Dielectric energy-storage capacitors are of great importance for modern electronic technology and pulse power systems. However, the energy storage density (W rec) of dielectric capacitors is much lower than lithium batteries or supercapacitors, limiting the development of dielectric materials in cutting-edge energy storage systems. This study presents a single-phase BaTiO 3 -based high-entropy (BT-H) ceramic, which is synthesized using a conventional solid-state reaction method. It is found that the BT-H ceramic exhibits a remarkable energy storage performance, with a W rec of 5.18 J/cm3 and an ultrahigh η of 93.7% at 640 kV/cm electric field. Moreover, it also features wide temperature stability and excellent frequency stability. It is proposed that the introduction of high entropy enhances the random electric field and stress field, leading to lattice distortion and reduction of nanometer domain size, which in turn reduces remnant polarization and increases electric breakdown strength. This research provides a novel approach to improve the energy storage performance of ceramics through the high-entropy strategy. • High-entropy engineering could enhance the energy storage performance of dielectric capacitors. • An ultrahigh W rec of 5.18 J/cm3 and η of 93.7% at 640 kV/cm electric field were achieved in the BT-H (Mg) ceramics. • The BT-H ceramics exhibit remarkable energy storage performance stability. [ABSTRACT FROM AUTHOR]

• High-entropy engineering. • The activation energy. • Thermal stability. The utilization of a high entropy approach for the design of high-performance perovskite dielectric capacitors has been gaining much attention for the development of next-generation pulse power capacitors. Despite this, there are still challenges to further enhance their energy storage density and efficiency. To address this, a high-entropy strategy is proposed to significantly improve the energy storage characteristics of ceramics by increasing the configurational entropy and delaying saturation polarization. This approach has resulted in an ultra-high recoverable energy storage density (W rec) of 7.16 J/cm3 and a high efficiency (η) of 93.3 % for 0.8[0.65(Bi 0.5 Na 0.5)TiO 3 -0.35SrTiO 3)]-0.2[Ba(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 Nb 0.2)O 3 ] (abbreviated as 0.8BNST-0.2Ba(5 M)O) ceramic. The inclusion of Ba(5 M)O high entropy oxides has resulted in slender polarization–electric field hysteresis loops with delayed polarization saturation. The increase in atomic configuration entropy, degree of atomic disorder and lattice distortion due to the Ba(5 M)O high entropy oxides, has led to an increase in breakdown field, improved energy storage density and efficiency. Furthermore, excellent thermal stability (30–150 ℃), superior frequency stability (5–1000 Hz), and robust fatigue (100–105 cycles) endurance were achieved. The high entropy strategy has been demonstrated to be an effective method for the design of novel capacitors with superior energy storage performance. [ABSTRACT FROM AUTHOR]

In this work, the electrocaloric (EC) effect was studied in the (100- x)BaHf 0.2 Ti 0.8 O 3 - x Ba 0.94 Sm 0.04 TiO 3 (BHT- x BST) ceramics fabricated by the conventional solid-reaction method. By tuning composition to their diffuse phase transition (DPT), invariant critical point (ICP) and first-order phase transition (FPT), the large electrocaloric response with a temperature change of ΔT = 0.46 °C (at 64 °C) under 30 kV/cm and an electrocaloric strength of ΔT/ΔE = 0.18 K mm/kV under 12 kV/cm were achieved in BHT-70BST. In addition, BHT-50BST shows a broad EC working temperature window from 28 °C to 68 °C because of its diffusion behavior near the ferroelectric-to-paraelectric phase transition and multiphase coexistence. The maximum ΔT of BHT-50BST is larger than that of BHT-40BST with only diffusion character but no multiphase coexistence. This work may provide a design strategy to enhance EC performance with a broad working temperature region in lead-free rare-earth doped BaTiO 3 -based ceramics by combining the diffusion behavior, multiphase coexistence and heterovalent substitution. [ABSTRACT FROM AUTHOR]

The lead-free Ba 0.53 Sr 0.47 TiO 3 (BST) thin films buffered with La 0.67 Sr 0.33 MnO 3 (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO 3 substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher E b. Therefore, the recoverable energy density (W rec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm3 for the LSMO thickness of 30 nm up to 51.2 J/cm3 for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 108 electrical cycles with only a slightly decrease of W rec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors. [ABSTRACT FROM AUTHOR]

• Local phase coexistence enhances the ESPs of the (1− x)BNT- x SLZT ceramics. • The W rec of 5.09 J/cm3 and η of 88% are achieved in 0.67BNT-0.33SLZT ceramic. • The ceramic displays good thermal stability from 0 °C to 200 °C. • The coexistence of P 4 bm and Pm -3 m phases increases the E b of the ceramic. Dielectric capacitors with excellent energy storage performance are highly desirable for electronic industry. Although many excellent studies have been carried out on energy-storage dielectric materials, the explanation of their macroscopic electrical properties from the microscopic point of view remains scarce. In this work, (1- x)Bi 0.5 Na 0.5 TiO 3 - x Sr 0.7 La 0.2 Zr 0.15 Ti 0.85 O 3 ((1- x)BNT- x SLZT) relaxor ceramics are designed and fabricated. The recoverable energy density of 5.09 J/cm3 and efficiency of 88% are achieved in 0.67BNT-0.33SLZT ceramic. The ceramic also displays an excellent thermal stability in a wide temperature range (0–200 °C). The good performance of the ceramics is attributed to their heterogeneous structure which contains two different local phases after composition modification. Micro-structure is then validated by the Rietveld refinement and transmission electron microscopy analysis. Moreover, the decrease in domain size and enhancement in domain reversibility are also observed in the sample. The delayed polarization saturation and increased electric field strength significantly enhance the energy storage properties of the ceramics. This work indicates that constructing local phase coexistence is an effective method for obtaining high-performance energy storage ceramics, and may provide a guideline for designing and preparation of dielectric energy storage ceramics with superior properties. [ABSTRACT FROM AUTHOR]

• Local phase coexistence enhances the ESPs of the (1− x)BNT- x SLZT ceramics. • The W rec of 5.09 J/cm3 and η of 88% are achieved in 0.67BNT-0.33SLZT ceramic. • The ceramic displays good thermal stability from 0 °C to 200 °C. • The coexistence of P 4 bm and Pm -3 m phases increases the E b of the ceramic. Dielectric capacitors with excellent energy storage performance are highly desirable for electronic industry. Although many excellent studies have been carried out on energy-storage dielectric materials, the explanation of their macroscopic electrical properties from the microscopic point of view remains scarce. In this work, (1- x)Bi 0.5 Na 0.5 TiO 3 - x Sr 0.7 La 0.2 Zr 0.15 Ti 0.85 O 3 ((1- x)BNT- x SLZT) relaxor ceramics are designed and fabricated. The recoverable energy density of 5.09 J/cm3 and efficiency of 88% are achieved in 0.67BNT-0.33SLZT ceramic. The ceramic also displays an excellent thermal stability in a wide temperature range (0–200 °C). The good performance of the ceramics is attributed to their heterogeneous structure which contains two different local phases after composition modification. Micro-structure is then validated by the Rietveld refinement and transmission electron microscopy analysis. Moreover, the decrease in domain size and enhancement in domain reversibility are also observed in the sample. The delayed polarization saturation and increased electric field strength significantly enhance the energy storage properties of the ceramics. This work indicates that constructing local phase coexistence is an effective method for obtaining high-performance energy storage ceramics, and may provide a guideline for designing and preparation of dielectric energy storage ceramics with superior properties. [ABSTRACT FROM AUTHOR]

• Ca2+ and Sr2+ can increase the stability of antiferroelectric phase while Ba2+ decreases it. • An enhanced negative ECE of Δ T around − 10.6 K was obtained in the Pb 0.9 Sr 0.1 ZrO 3 thin film at room temperature. • The modification of antiferroelectric-ferroelectric phase transition is an effective strategy to enhance the negative electrocaloric effect in antiferroelectric thin films. In the Pb 0.9 Sr 0.1 ZrO 3 thin film, an enhanced negative electrocaloric effect (ECE) has been observed based on the Maxwell relation, with Δ T of around − 10.6 K under 450 kV/cm at room temperature, as compared with the pristine PbZrO 3 thin film (with Δ T of around −7.3 K under 300 kV/cm at 361 K), as shown in the figure. Our work demonstrates that modifying antiferroelectric-ferroelectric phase transition is an effective way to enhance the negative ECE in antiferroelectric thin films. [Display omitted] Electrocaloric effect (ECE) in dielectric materials has attracted much attention due to its promising applications in solid-state cooling devices. In this work, alkaline-earth doped PbZrO 3 antiferroelectric thin films (Pb 0.9 A 0.1 ZrO 3 (A=Ca, Sr, and Ba)) were deposited by a sol-gel method and its antiferroelectric-ferroelectric phase competition as well as the negative ECE were studied. It is found that Ca2+ and Sr2+ expand the antiferroelectric phase region while Ba2+ reduces it, due to the different ion radii of these alkaline-earth elements. As a result, the Pb 0.9 Sr 0.1 ZrO 3 thin film exhibits an enhanced negative ECE with Δ T of around − 10.6 K under 450 kV/cm whereas the Pb 0.9 Ba 0.1 ZrO 3 thin film shows a decreased negative ECE with Δ T of around − 2.5 K under 200 kV/cm, as compared with the pristine PbZrO 3 thin films (with Δ T of around −7.3 K under 300 kV/cm). This work provides an effective method to enhance the negative ECE of antiferroelectrics in electrical cooling applications by adjusting their antiferroelectric to ferroelectric phase transition. [ABSTRACT FROM AUTHOR]