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The ceramic capacitors with excellent energy storage properties and wide operating temperature are the main challenges in power system applications. Here, the lead‐free (1‐x)Bi0.5Na0.5TiO3‐xCaTiO3 (abbreviated as BNT‐xCT) ceramics were synthesized through solid‐state reaction method. The introduction of CT reduced the temperature of permittivity peak of BNT ceramic, guaranteeing excellent thermal stability over a wide temperature range of −100 ∼ 136°C. Meanwhile, the long‐range order structure of BNT was destructed by structural distortion, and the relaxor behavior was enhanced after doping CT. Moreover, the direct current breakdown strength was improved from 203 to 455 kV/cm, and the high recoverable energy density (Wrec ∼ 2.74 J/cm3) with high efficiency (η ∼ 91%) was achieved for BNT‐0.25CT ceramic, along with a fast discharge speed (t0.9 ∼ 110 ns) superior cycle stability and thermal stability. Those properties enabled a promising practical prospect of BNT‐CT ceramics. [ABSTRACT FROM AUTHOR]

0.8Sr0.875Pb0.125TiO3–0.2Bi(Mg0.5Zr0.5)O3–x(K0.5Na0.5)NbO3 (0.8SPT–0.2BMZ–xKNN, x = 0.015–0.035) ceramics are calcined by solid‐state methods. The phase structures, energy storage, and discharge performance, as well as their temperature stability, are systematically investigated. All samples are verified as a single perovskite structure by X‐ray diffraction (XRD) results. The x = 0.03 ceramic possesses excellent temperature stability, meeting the X7R standard for pulsed power capacitors. According to P–E loops calculation, the recoverable energy storage density (Wrec) and efficiency (η) are 1.27 J cm−3 and 90% at 240 kV cm−1, respectively. Moreover, Wrec and η also have good temperature insensitivity over a wide temperature range from 30 to 150 °C. The x = 0.03 ceramic has a high discharge energy density of ≈2.05 J cm−3 and a large power density of ≈143 MW cm−3 at 300 kV cm−1. The excellent temperature insensitivity and large discharge energy density exhibit that the x = 0.03 sample is a potential candidate material for pulsed power capacitors with a wide temperature range. [ABSTRACT FROM AUTHOR]

(1‐x)Sr0.7Pb0.15Bi0.1TiO3‐xBi4Ti3O12 ((1‐x)SPBT‐xBIT, x = 0‐0.125) bulk ceramics were developed and calcined via the solid‐state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT‐0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT‐0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT‐0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range. [ABSTRACT FROM AUTHOR]

In this paper, the (1−x)BaTiO3-xBi(Zn1/2Zr1/2)O3 (x = 0.04-0.20) solid solutions were prepared using conventional solid-state reaction method. The X-ray diffraction results showed that all samples were crystalized as the perovskite structure, and there was no secondary phase in whole compositional range. For x = 0.04, the ceramics were in tetragonal phase, and transformed to a pesudocubic phase for x ≥ 0.08 at ambient temperature. Temperature-dependent dielectric measurements indicated a crossover from ferroelectric behavior to relaxor-like characteristics. As the BZZ content increased, the polarization-electric field (P-E) hysteresis loops became slimmer, and the discharge energy density increased firstly, but dropped. For x = 0.12, the maximum discharge energy density was 0.758 J/cm3 at 100 kV/cm, and the corresponding energy efficiency was 98%, indicating that (1−x)BaTiO3-xBi(Zn1/2Zr1/2)O3 ceramics were promising candidates for energy storage applications. [ABSTRACT FROM AUTHOR]

We report herein on the energy storage and discharge properties of the relaxor ferroelectric ceramic Sr0.8Pb0.1Bi0.1TiO3 (SPBT). This material has a slanted hysteresis loop, and all samples show low remnant polarization and low coercive field, which leads to a high discharge efficiency. The maximum polarization is 10.1 μC/cm2, the minimum coercive field is 0.229 kV/cm, and the maximum efficiency is 94.2%. The discharge current waveforms are sinusoidal, the first discharge period is 140 ns, and the power density is approximately 4.2 × 107 W/kg. The high discharge speed and high discharge power density indicate that SPBT ceramics are very promising materials for energy storage applications. [ABSTRACT FROM AUTHOR]

Abstract: NiNb2O6‐BaTiO3 ceramics were prepared using a solid‐state reaction method, and the effects of the addition of NiNb2O6 on the dielectric properties and energy‐storage characteristics of BaTiO3 were investigated systematically. We used XRD to show that the obtained NiNb2O6‐BaTiO3 ceramics possess a single perovskite structure. The addition of NiNb2O6 improves the energy density efficiency and leads to a decrease of the dielectric loss to less than 1 %. Moreover, optimum performances of the BaTiO3 ceramics can be achieved by the addition of 1.0 mol % NiNb2O6, at which content the obtained ceramic satisfies the X7R specification. The addition of NiNb2O6 stabilizes the crystalline lattice, which enhances the temperature stability of the dielectric properties accordingly. [ABSTRACT FROM AUTHOR]

(1−x)Ba 0.4 Sr 0.6 TiO 3 -xBi(Mg 0.5 Ti 0.5)O 3 ((1−x)BST-xBMT) relaxor ferroelectric ceramics were prepared by a conventional solid-state method. In this work, the microstructure, dielectric properties, and pulsed charge–discharge properties were investigated. The doping of BMT caused a decrease in the surface energy and grain boundary energy, and contributed to the formation of polar nanoregions (PNRs). The existence of PNRs was confirmed by piezoresponse force microscopy measurements (PFM) on the 0.8BST-0.2BMT ceramic. The PNRs responded quickly under an AC voltage, thus the pulsed charge–discharge time was short (<80 ns), aiming to realize time compression to improve the power density (P D). The PNRs were not closely connected to each other and adverse to the formation of leakage current and pinning, thus inhibiting charge transfer at the grain boundaries and contributing to the high energy storage efficiency (η ∼ 93%). In addition, the 0.8BST-0.2BMT ceramic also displayed excellent temperature stability. The capacitance-temperature dependence satisfied the requirement of X8R (−55–150 °C, ΔC/C 25 °C ≤ ±15%), and η had no obvious fluctuation in the temperature range from 25 °C to 150 °C. This study could provide a successful method to achieve a temperature stable and high η , and a fast charge–discharge process. [ABSTRACT FROM AUTHOR]

Ba 0.4 Sr 0.6 TiO 3 is regarded as one of promising material for energy-storage capacitors. However, its dielectric breakdown strength is relatively low (∼ 15 kV/mm) and remnant polarization (P r) is large. These deficiencies lead to inadequate recoverable energy storage density (W rec) and efficiency (η). Herein, novel (1-x)Ba 0.4 Sr 0.6 TiO 3 - x Bi 0.5 La 0.5 (Zn 0.5 Sn 0.5)O 3 (BST- x BLZS, 0.08 ≤ x ≤ 0.14) ceramics were prepared to introduce relaxation and obtain smaller average grain size compared with pure BST. This strategy effectively inhibits the production of oxygen vacancies and titanium ions from changing valence, thereby increasing resistivity and reducing grain size, which result in the enhanced BDS. Meanwhile, enhanced relaxation results in near-zero P r and η is highly improved. When x = 0.12, BDS was significantly enhanced to 48 kV/mm and high W rec (2.76 J/cm3) with preferable η of 92% was achieved simultaneously. Excellent temperature and frequency stability of energy storage performance were obtained either. Moreover, the 0.88BST-0.12BLZS ceramic also possesses large power density (P D = 48.4 MW/cm3) with good temperature and fatigue stability. Meanwhile the fast discharge rate (t 0.9 around 200 ns) was obtained. These properties show that 0.88BST-0.12BLZS relaxor ceramic exhibits great prospects for practical pulse power applications. [ABSTRACT FROM AUTHOR]

In this paper, the dense perovskite structure ceramics (Na 0.3 Bi 0.3 Ba 0.04 Sr 0.36) 1-x Ca x Ti 1-x Nb x O 3 were investigated. The long-range order structure was destructed by structural distortion, and the relaxor behavior was enhanced after the co-doping with Ca and Nb. Meanwhile, the restraint of oxygen vacancy resulted in low leakage current density and small grain size with the increase of breakdown strength ranging from 210 to 280 kV/cm. The high recoverable energy density (W rec = 2.94 J/cm3) with high efficiency (η = 91.04%) was obtained at x = 0.03, along with fast discharge speed (t 0.9 –180 ns), high power density (P D = 56.15 MW/cm3), superior cycle stability and thermal stability. The properties guaranteed a promising and practical prospect in pulsed power systems. [ABSTRACT FROM AUTHOR]

In this study, novel lead-free (1- x)Sr 0·7 Bi 0·2 TiO 3 - x La(Mg 0·5 Zr 0.5)O 3 ((1- x)SBT- x LMZ) ceramics were designed and fabricated by the conventional solid-state reaction method. The dielectric performance, energy storage characteristics and charge-discharge behavior of the ceramics were systematically investigated. Specifically, the temperature stability of dielectric constant is improved by doping SBT with LMZ. On a separate note, BDS is also enhanced ascribed to the reduction of the grain size. Consequently, the 0.87SBT-0.13LMZ exhibits high critical electric field of 340 kV/cm with ultrahigh efficiency (η) of 98.2% and recoverable energy storage density (W rec) of 1.22 J/cm3. Moreover, pulsed charge-discharge test elucidates that 0.87SBT-0.13LMZ possesses great thermal stability (30 °C–150 °C) along with a fast discharge period of 0.125 μs, high power density (P D) of 72.38 MW/cm3 as well as a high pulsed discharge energy density (1.2 J/cm3) at 380 kV/cm. Based on these outstanding characteristics, the 0.87SBT-0.13LMZ is considered as a potential candidate for pulse systems. [ABSTRACT FROM AUTHOR]

Dielectric capacitors have been extensively studied in electronic and power systems based on their high power density and ultra-fast discharge rates. In this study, the dielectric, energy storage and charge-discharge properties of Sr 0.7 Bi 0.2 TiO 3 -based lead-free relaxor ferroelectric ceramic were investigated. The dielectric breakdown strength was significantly improved by introducing the rare earth element Nd, which was attributed to the rise in resistivity and large band gap. The results show that Sr 0.7 Bi 0.15 Nd 0.05 TiO 3 obtain a high recoverable energy storage density of 2.34 J/cm3 with high efficiency of 92%. In addition, pulsed charge-discharge tests demonstrated that Sr 0.7 Bi 0.15 Nd 0.05 TiO 3 possesses a high power density of 73.5 MW/cm3, a short discharge period of 0.1 μs, and a pulsed discharge energy density of 2.0 J/cm3. Meanwhile, the energy storage performance of Sr 0.7 Bi 0.15 Nd 0.05 TiO 3 exhibits excellent stability of temperature, frequency and cycling. This work provides a systematic study and a new strategy for enhancing the performance of SBT ceramics. • Nd doping broadens the dielectric peak and enhances the relaxor properties. • The improved activation energy and band gap increase the breakdown strength. • Ceramics achieve excellent energy storage density and efficiency at 360 kV/cm. • Ceramics possess excellent charge-discharge performance and thermal stability. [ABSTRACT FROM AUTHOR]

• An phase-structure and relaxation regulation was constructed in NSN-BF RAFEs. • A large W rec (4.0 J/cm3) and η (80 %) was gained in NSN-BF RAFEs by regulation. • Superior charge–discharge properties and functional reliabilities were confirmed. Lead-free NaNbO 3 -based antiferroelectric (AFE) ceramics are highly considered as promising substitutes of lead-based ones in dielectric energy-storage field. However, their low breakdown strength and large electric hysteresis loss originating from the field-induced metastable ferroelectric (FE) Q phase and/or AFE P phase still remains challenging, which severely impedes the further improvement of energy-storage performances. Herein, an effective phase-structure and relaxation regulation via A-site cation substitution strategy has been proposed to solve this issue. The phase-structures of the designed NN-based AFE ceramics evolve from orthorhombic P phase to R phase accompanying with the enhancement of relaxation behavior. Accordingly, an effective transformation from a plump and pinched polarization–electric field (P – E) hysteresis loop to a slim and slanted one has undergone, contributing to superior energy-storage performances. Noticeably, an expected large recoverable energy density (W rec) of 4.0 J/cm3 with a high energy conversion efficiency (η) of 80.0 % was realized in 0.94(Na 0.88 Sm 0.04 NbO 3)-0.06(BiFeO 3) relaxor AFE ceramics at 460 kV/cm. Meanwhile, a great discharge energy density (W dis) of 1.2 J/cm3 and a large power density (P D) of 92.4 MW/cm3 were achieved at 200 kV/cm. Furthermore, the favorable functional reliabilities in frequency, temperature, and fatigue cycle were also confirmed. These results not only demonstrate the great potential of NaNbO 3 -based relaxor AFE ceramics for dielectric energy-storage applications, but also confirm the validity of the strategy proposed in this work to obtain superior energy-storage performances. [ABSTRACT FROM AUTHOR]

Ferroelectric (1-x)Sr 0.875 Pb 0.125 TiO 3 -xBi(Mg 0.5 Zr 0.5)O 3 ((1-x)SPT-xBMZ, x = 0-0.2) ceramics with high discharge efficiency and power density were synthesized via a conventional solid-state sintering method. The prepared (1-x)SPT-xBMZ ceramics were detected as a pure perovskite structure and a dense microstructure, and a typical relaxor behavior and an excellent temperature stability were also observed. Although there is no direct correlation between the degree of diffuseness and the maximum polarization, the high degree of diffuseness can reduce the remanent polarization and significantly improve energy storage and release characteristics of ferroelectric ceramics. Based on a polarization electric-field loop measurement, a recoverable energy storage density of 0.762 J/cm3 and a very high efficiency of 96.34% are achieved when x = 0.2 under 150 kV/cm. The energy storage properties of 0.8SPT-0.2BMZ ceramic exhibit good temperature stability (25−130 °C) and frequency stability (2−80 Hz). In a practical charge-discharge circuit testing, a short discharge pulse-period about 94 ns, a high discharge energy density of 1.7 J/cm3 and an ultra-high-power density of 62.8 MW/cm3 are obtained for the 0.8SPT-0.2BMZ ceramic at 240 kV/cm. The results indicate that the 0.8SPT-0.2BMZ ceramic is a promising dielectric material for high-power pulse capacitors. [ABSTRACT FROM AUTHOR]

Lead-free (Na 0.5 Bi 0.5) 0.4 Sr 0.6 TiO 3 - x K 0.73 Bi 0.09 NbO 3 (abbreviated as NBST- x KBN) ceramics with perovskite structure were prepared by a conventional solid-state reaction method. NBST ceramics modified with KBN content demonstrate strong relaxor behavior. When x = 0.05, the optimal energy storage density (1.79J/cm3), improved recoverable energy efficiency (91.02%) and the maximum dielectric breakdown strength (22.2 kV/mm) are obtained. The discharge energy density of NBST-0.05KBN are measured under the electric field from 10 kV/mm to 16 kV/mm, exhibiting good discharge energy density (1.20J/cm3) at 16 kV/mm. Complex impedance plots of NBST- x KBN exhibit great resistivity of the ceramics. In all, these results indicate that NBST- x KBN is a potential candidate for energy storage applications. [ABSTRACT FROM AUTHOR]

A series of (1- x)(Sr 0.7 Ba 0.3) 5 LaNb 7 Ti 3 O 30 – x (Bi 0.5 Na 0.5)TiO 3 (x = 0.1–0.4) ceramics with tungsten bronze structure were prepared by solid state reaction. Phase composition, microstructure and energy storage properties were studied. When x = 0.3, excellent thermal stability satisfying the X7R specification was obtained and its energy storage as well as charge-discharge performances were further evaluated. Release energy density (W re) of 0.77 J/cm3 and an energy storage efficiency of 97.3 % were detected at a low electric field of 20 kV/mm. Under the electric field of 10 kV/mm, the change of W re in the temperature range of −55 °C to 125 °C is less than 15 % compared to room temperature. Short discharge period (∼0.17 μs), high power density (61.2 MW/cm3) and high discharge energy density (2.45 J/cm3) were evaluated by charge-discharge tests. Excellent thermal stability, high energy storage efficiency and high power density indicate that 0.7(Sr 0.7 Ba 0.3) 5 LaNb 7 Ti 3 O 30 –0.3(Bi 0.5 Na 0.5)TiO 3 ceramic is a promising pulse capacitor for working over a wide temperature range. [ABSTRACT FROM AUTHOR]

• The introduction of Ca inhibits the grain growth and reduces oxygen vacancies. • The optimal composition exhibits ultra-high dielectric breakdown strength. • The optimal composition exhibits ultra-high energy storage density and efficiency. • The optimal composition shows excellent stability of temperature and frequency. • The optimal composition exhibits high power density. Sr 0.7 Bi 0.2 TiO 3 with high relaxor behavior and energy storage efficiency (η) is expected to be applied in power energy storage capacitors. However, its energy storage density is limited by the relatively low dielectric breakdown strength (DBS). Herein, Sr 0.7 Bi 0.2 Ca x TiO 3 (SBT-xC, x = 0 ∼ 0.15) was prepared to decrease the average grain size of Sr 0.7 Bi 0.2 TiO 3. This can effectively eliminate the oxygen vacancy and decrease the electrical conductivity and leakage current, which result in the enhanced DBS. Meanwhile, Ca doping increases the relaxor behavior and dielectric constant. When x = 0.1, the composition exhibits high DBS of 480.2 kV/cm and excellent energy storage properties, such as high energy storage density of 2.1 J/cm3 with high η of 97.6 % at 290 kV/cm, considerable thermal stability and great frequency stability. Moreover, SBT-0.1C shows high power density of 50.1 MW/cm3. These results suggest that SBT-0.1C is a potential candidate for high performance dielectric energy storage applications. [ABSTRACT FROM AUTHOR]

In this work, a new (Sr 0.7 Ba 0.3) 5 LaNb 7 Ti 3 O 30 system ceramic with a filled tetragonal tungsten bronze structure was proposed and fabricated by the traditional solid phase method. Crystal structure, relaxor behaviors and energy storage capabilities were studied. Large relaxor activation energy indicates a "weakly coupled relaxor" mechanism, which is advantageous for obtaining better energy storage performance, and lower conductance activation energy can further prove the formation of the filled tungsten bronze structure. More importantly, a dielectric breakdown strength of up to 35.5 kV/mm was obtained. The releasable energy density and efficiency at 24 kV/mm are 1.36J/cm3 and 91.9%, respectively. In addition, due to the high current density and high dielectric breakdown strength, a current density of 477.5 A/cm2 and a power density of 42.9 MW/cm3 are achieved, meaning that SBLNT ceramic is a potential candidate dielectric ceramic for energy storage. [ABSTRACT FROM AUTHOR]

In this work, we designed novel lead-free relaxor ferroelectric ceramics of (1- x)BaTiO 3 - x Bi(Ni 1/2 Sn 1/2)O 3 (abbreviated as (1- x)BT- x BNS, with x = 0–0.20). With an increasing concentration of BNS, (1- x)BT- x BNS solid solutions displayed a phase transition from tetragonal symmetry to pseudocubic symmetry with highly diffusive and frequency-dependent relaxor ferroelectric behavior. Modified by BNS, (1- x)BT- x BNS ceramics yielded slim polarization-electric field (P - E) loops and improved energy-storage performances. The optimal energy storage properties can be achieved at x = 0.10, and samples showed a high recoverable energy density of 2.526 J/cm3 and a remarkably high energy efficiency of 93.89% under 240 kV/cm simultaneously at ambient temperature, which represent enhancements by 925% and 286%, respectively, over pure BaTiO 3. The energy storage characteristics of the 0.9BT-0.1BNS ceramic manifested good thermal stability (−55–150 °C) and frequency stability (10 Hz-1 kHz), with a variation in recoverable energy density of less than 10%. Meanwhile, the pulsed charging-discharging measurement showed that the 0.9BT-0.1BNS ceramic had a fast discharge period of 67 ns and a large power density of 19 MW/cm3. Due to the outstanding characteristics, there is potential for this new and environmentally friendly BT-based ceramic to be used in high-power pulse capacitor applications. [ABSTRACT FROM AUTHOR]

Over the past few years, organic flow batteries have gained immense attention owing to their potential for large-scale energy storage applications and modifiable properties. Organic redox couples usually involve only one type of counter-ion for ion exchange membranes, and hence provide opportunities to use low-cost membranes in organic flow batteries. In this study, we prepared a sulfonated poly (ether ether ketone) (sPEEK) membrane for application in acidic flow batteries of 1,2-dihydroxybenzene-3,5-disulfonic acid/anthraquinone-2-sulfonic acid. The proton conductivity of the prepared sPEEK membrane was 50% lower than that of Nafion-212 membrane. However, the Coulombic efficiency of the sPEEK cell was similar to that of Nafion cell, and the voltage efficiency was 0.99%–2.66% higher than that of Nafion cell at different current densities. The cell using the sPEEK membrane also exhibited long-term stability, retaining 96.93% reversible capacity after 100 charge/discharge cycles at the current density of 100 mA cm−2. The results of symmetric cell cycling indicated that the decay of reversible capacity in this organic flow battery system was mainly due to the instability of organic compounds in the positive electrolyte, which was also confirmed by the self-discharge measurements of the sPEEK cell. These results demonstrate that the sPEEK membrane is highly suitable for organic flow batteries. These results will be helpful for realizing cost-effective energy storage systems. Image 1 • Low cost sPEEK membrane is reliable using in quinone-based organic flow battery. • SPEEK membrane shows better energy efficiency than Nafion-212 in the cell. • Long term cycling stability of the sPEEK cell has been demonstrated. • Low capacity loss of organic flow battery makes it flexible to choose membrane. [ABSTRACT FROM AUTHOR]

Abstract In this study, 0.95 Sr 0.7 Ba 0.3 Nb 2 O 6 -0.05CaTiO 3 - x wt% Er 2 O 3 ceramics (SBNCTE x ; x = 0–5) were synthesized using traditional solid-state method, and we investigated the microstructure, energy storage properties as well as the relationship between dielectric breakdown strength and interfacial polarization. As compared with pure 0.95 Sr 0.7 Ba 0.3 Nb 2 O 6 -0.05CaTiO 3 ceramics, the Er 2 O 3 dopants suppressed the grain growth of SBNCTE x , and the doped ones showed the dense microstructure. The secondary phase was found for x ≥ 1 according to the EDS results, and the influence of the secondary phase on relative dielectric breakdown strength has also been studied. The dielectric breakdown strength increased from 18.1 kV/mm to 34.4 kV/mm, which is good for energy storage. The energy storage density of 0.28 J/cm3 and the energy storage efficiency of 91.4% were obtained in the SBNCTE5 ceramics. The results indicate that SBNCTE ceramics can be used as energy storage capacitors. [ABSTRACT FROM AUTHOR]

• Homogeneous phase transition restricts the abrupt variation of polarization. • Reduction of oxygen vacancy concentration improves the breakdown strength. • The activation and ordered arrangement of PNRs enhance the polarization. Lead-free energy storage ceramics have attracted a large concentration for their significant role in pulsed power technology. Here, environmentally friendly (Sr 0.7 Ca 0.3) 1−1.5x Bi x TiO 3 relaxor ferroelectric ceramics are systematically studied. The introduction of Bi 2 O 3 can enhance polarization. As the Bi 2 O 3 content increases, the dielectric constant rises from 300 to 774, while the dielectric loss is less than 0.5% under a measurement frequency of 1 kHz. For the Sr 0.49 Ca 0.21 Bi 0.2 TiO 3 ceramic, an energy storage density (W) of 2.035 J cm−3 and a high energy storage efficiency (η) of 91.84% achieved under an electric field of 260 kV cm−1. The variation rate of the dielectric constant is less than 15% (compared with the capacitance at 25 °C) in the temperature range of − 55–125 °C, meeting the requirement of the EIA X7R specification, and the W and discharge energy density (W d) also exhibit desirable temperature stability in the temperature range of 30 °C to 150 °C. These results are related to the homogeneous phase transition and low concentration of oxygen vacancies. The thermal activation of polar nanoregions (PNRs) partially compensates for the reduction of polarization caused by lattice expansion, which also contributes to the temperature stability. Taken together, the results of this study indicate the Sr 0.49 Ca 0.21 Bi 0.2 TiO 3 ceramics have potential as a target for developing high energy storage lead-free ceramic capacitors. [ABSTRACT FROM AUTHOR]

• An excellent thermal stability following X7R specification compared with other typical BNT-based ceramics. • ZT5 ceramic possesses the high W rec of 3.06 J/cm3 and high η of 92.91%. • A fast discharge speed t 0.9 ~ 170 ns and high P D ~ 60.46 MW/cm3 were achieved. • The energy density is degraded around 3% over 100000 cycles. It is challengeable to winden the operating temperature and optimize the energy storage properties of ceramic capacitors in power system applications. Here, the lead-free (1-x) Na 0.3 Bi 0.3 Ba 0.04 Sr 0.36 TiO 3 -xZnTa 2 O 6 (BNBST-xZT) ceramics were designed. The introduction of ZT into BNBST reduced the temperature of permittivity peak of BNBST ceramic, which guaranteed the superior thermal stability following X7R specification. Due to the compositional disorder and structural distortion, the ferroelectric order of BNBST was broken, mitigating polarization saturation. The high recoverable energy density (W rec = 3.06 J/cm3) with high efficiency (η = 92.91%) was achieved under 270 kV/cm. The fast discharge speed (t 0.9 ~ 170 ns), large power density (P D = 60.46 MW/cm3), thermal stability, and superior cycle stability were evaluated to illustrate its promising practical prospect using in pulsed power capacitor devices. [ABSTRACT FROM AUTHOR]

• A novel type of lead- and bismuth-free TTB relaxor is obtained. • The relationship between structure and electrical behavior is studied in detail. • Enhanced relaxation and high BDS are obtained based on B-site substitution. • The current ceramics show the high W re of 2.03 J/cm3 and the η of 94%. • Excellent charging-discharging performance of W dis of 2.22 J/cm3 and 151.1 MW/cm3 of P D are achieved. Based on B-site substitution, a series of Sr 1.88 La 0.12 NaNb 4.88−x Ta x Ti 0.12 O 15 tungsten bronze ceramics were prepared by traditional solid-reaction. The influence of Ta replacement on dielectric relaxor, electrical and energy storage properties has been studied in detail. The change of dielectric properties deviates from the previous crystal chemical framework, and is closely related to the structural distortion caused by the special electronic configuration of Ta. In addition, an enhanced dielectric breakdown strength was obtained, which benefited from the dense microstructure, improved insulation and widened band gap. Finally, under the combined influence of good relaxation and high dielectric breakdown strength, an energy storage density of 2.03 J/cm3 and an efficiency of 94% were achieved. More importantly, the charging-discharging performance has also been evaluated. The discharge energy density of 2.22 J/cm3 and the power density of 151.1 MW/cm3 indicate that the present ceramics are promising as high-power energy storage capacitor applications. [ABSTRACT FROM AUTHOR]

Perovskite structure (1-x)(0.8Bi 0.5 Na 0.5 TiO 3 -0.2Ba 0.3 Sr 0.7 TiO 3)-xNaNbO 3 (BNBST-xNN, x ≤ 0.3) ceramics were fabricated by solid-state reaction method. The grain growth was suppressed after adding NaNbO 3 into 0.8Bi 0.5 Na 0.5 TiO 3 -0.2Ba 0.3 Sr 0.7 TiO 3 ceramic, and XRD patterns revealed that solid solutions were formed with NaNbO 3 at 0–0.2. With the rising amount of NaNbO 3 , both relaxor characteristics and dielectric temperature stability were enhanced. The BNBST-0.1NN solid solution displayed a high recoverable energy storage density of 2.26 J/cm3 with energy storage efficiency of 87.34% at 180 kV/cm and exhibited a short time of less than 1 μs for discharged energy density reached to 90% of its saturated value. Furthermore, the ceramic for x = 0.1 displayed a permittivity of 2601 at 150 °C and showed a wide range from 20 to 300 °C for permittivity deviation Δε/ε 150°C less than ±15%, exhibiting a superior thermal stability of permittivity. In addition, a reduction around 5% in W dis after 106 cycles indicated its excellent fatigue characteristics. • Lead-free BNBST-xNN ceramics for energy storage were successfully prepared. • A high releasable energy storage density of 2.26 J/cm3 was obtained. • BNBST-0.1NN ceramic exhibited good thermal stability and frequency stability. • The energy storage density of BNBST-0.1NN is degraded around 5% after 106 cycles. [ABSTRACT FROM AUTHOR]

• BDS is significantly enhanced in SBKT-2 wt. % Er 2 O 3 composite ceramics. • The transition mechanism of BDS is analyzed by numerical simulations (COMSOL). • SBKT-2 wt. % Er 2 O 3 shows high W (2.59 J/cm3) and η (83.9%) at high BDS (245 kV/cm). • SBKT-2 wt. % Er 2 O 3 exhibits both high W d (1.51 J/cm3) and P D (39.6 MW/cm3). • SBKT-2 wt. % Er 2 O 3 shows excellent stability of temperature, frequency and cycling. The development of lead-free dielectric ceramics with excellent energy storage properties has received extensive research attention. Herein, Er 2 O 3 modified Sr 0.35 Bi 0.35 K 0.25 TiO 3 (SBKT) composite ceramic is investigated. As 2 wt. % Er 2 O 3 is added, a certain amount of insulating second phase with fewer regions of high local electric field (numerically simulated by COMSOL) is formed, giving rise to the increase in the dielectric breakdown strength (BDS) due to the increased electrical resistivity and band gap, the decreased average grain size and the decreased leakage current density. This optimal composition exhibits many excellent energy storage properties, such as high energy storage density of 2.59 J/cm3, high recoverable energy storage density (W rec) of 2.17 J/cm3 with high efficiency (η) of 83.9% at 245 kV/cm, superior stability of temperature (<1% variation of W rec and η in −25 ~ 150 °C), frequency (~1.6% variation of W rec with ~3.6% variation of η in 10 ~ 500 Hz) and cycling (almost no change of W rec and η within 105 cycles), and high discharge energy density of 1.51 J/cm3 with high power density of 39.6 MW/cm3 at 200 kV/cm. In this work, we provide a novel strategy and understanding to design the advanced pulse energy storage ceramics. [ABSTRACT FROM AUTHOR]

Novel lead-free ceramics of (1- x)BaTiO 3 - x Bi(Mg 1/2 Sn 1/2)O 3 (abbreviated as (1- x)BT- x BMS, with x = 0–0.20) were fabricated through a solid-state reaction route. Introducing BMS into the BT host triggered a ferroelectric-to-relaxor phase transition, which yielded slim polarization-electric field (P - E) loops and enhanced energy-storage performances. The large recoverable energy density with 2.25 J/cm3 and high energy efficiency of 94% were obtained simultaneously under 240 kV/cm with x = 0.12. Furthermore, the energy storage characteristics of the 0.88BT-0.12BMS ceramics exhibited good temperature stability in the range of −55–150 °C, and great frequency stability in the range of 10–1000 Hz. Meanwhile, by means of pulsed charging-discharging evaluation, the 0.88BT-0.12BMS ceramics displayed a fast discharge period of 73 ns and a large power density of 27.7 MW/cm3. The results indicate that the elaborately designed 0.88BT-0.12BNS ceramics have promising potential for high-power pulsed capacitor applications. • Bi(Mg 1/2 Sn 1/2)O 3 doping can trigger a phase transition from ferroelectric to relaxor ferroelectric. • A large recoverable energy density of 2.25 J/cm3 and a high energy efficiency of 94% can be obtained simultaneously. • The energy properties show excellent thermal and frequency stability. • A large power density of 27.7 MW/cm3 can be obtained at 100 kV/cm. [ABSTRACT FROM AUTHOR]