Improved energy storage properties of Sr(Zr0.8Nb0.16)O3-doped Bi0.47Na0.47Ba0.06TiO3 ceramics with excellent temperature/frequency stability

Lead-free perovskite dielectric materials for capacitors have received wide concern in recent years, but their energy storage density and efficiency still cannot meet the growing application demand for practical applications. In this work, we prepared a lead-free relaxor ferroelectric ceramic of (1-x)Bi_0.47Na_0.47Ba_0.06TiO₃-xSr(Zr_0.8Nb_0.16)O₃, which was synthesized via a normal solid-state route. The microstructure, dielectric properties and energy storage behavior of the ceramics were explored. The ceramics can be well sintered and situated in the region where rhombohedral and tetragonal phases coexist. The addition of Sr(Zr_0.8Nb_0.16)O₃ (SZN) significantly extends the dielectric-temperature plateau between T_s and T_m and reduces the remnant polarization P_r, but the large saturation polarization P_s is still maintained. Besides, the doping of SZN enhances the relaxation of the material and increases the dielectric breakdown strength (DBS) from 50 kV/cm (x = 0) to 100 kV/cm (x = 0.04 and 0.06). Therefore, the ceramic with x = 0.06 exhibits a high discharging efficiency (η) of 71.1% and energy density (W) of 1.56 J/cm³ at 100 kV/cm and shows the superior thermal stability with the changes in recoverable energy density (W_rec) and η of less than 10% and 30% at the temperature range of 25–180 °C and the excellent frequency stability with the variations of W_rec and η of less than 1.8% and 1% at the frequency range of 10 Hz–100 Hz.     

(1-x)Bi0.5Na0.47Li0.03TiO3-xNaNbO3 lead-free ceramics with superior energy storage performances and good temperature stability

Dielectric capacitors show great potential in superior energy storage devices. However, the energy density of these capacitors is still inadequate to meet the requirement of energy storage applications. In this study, the Bi_0.5Na_0.47Li_0.03TiO₃-xNaNbO₃ (BNLT-xNN) ceramics were prepared via conventional solid-phase reaction. Results showed that NN can efficaciously enhance the breakdown strength (E_b) and the relaxation behavior of the BNLT ceramic because of the broken ferroelectric long-range order. When x = 0.3, the maximum E_b reached 350 kV/cm, at which the 0.7BNLT-0.3NN ceramic exhibited the high recoverable energy storage density (W_rec) of 4.83 J/cm³ and great efficiency (η) of 78.9%. The ceramic demonstrated good temperature stability at 20 °C-160 °C and excellent fatigue resistance. Additionally, the 0.7BNLT-0.3NN ceramic presented high power density (P_D; ～77.58 MW/cm³), large current density (C_D; ～861.99 A/cm²), and quite short discharge time (t_0.9; ～0.090 μs). These results indicated that the 0.7BNLT-0.3NN material has excellent energy storage properties and various application prospects.     

An effective strategy to realize superior high-temperature energy storage properties in Na0.5Bi0.5TiO3 based lead-free ceramics

To develop and fabricate environmentally friendly dielectric capacitors used in high-temperature environment, in this work, we prepare La³⁺ doped 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ lead-free relaxor ferroelectric ceramics with high and wide phase transition temperature. With the introduction of La³⁺, due to the enhancement of the A- and B- site cation ion disorder, the dielectric relaxation characteristics of the ceramics are more obvious. Therefore, the polarization-electric field loops become slimmer and the remnant polarization (P_r) reduces. In addition, because La³⁺ as a donor dopant has lower mobility than A-site cation ions in the ceramic matrix, the grain sizes decrease with increasing La³⁺ content, which significantly leads to an increase in the breakdown strength (E_b). As a result, both a large recoverable energy density (W_rec) of 1.92 J/cm³ and a high energy efficiency (η) of 85.7% are obtained in the ceramic with 12 mol% La³⁺ content. More importantly, even at 200 °C and a low driving electric field of 155 kV/cm, the W_rec and η of this kind of ceramic are still as high as 1.2 J/cm³ and 89.4%, indicating good temperature stability. This work provides an effective and simple way to prepare environmentally friendly dielectric capacitors that are applicable in high-temperature environment.     

Tailoring high energy density with superior stability under low electric field in novel (Bi0.5Na0.5)TiO3-based relaxor ferroelectric ceramics

Large energy storage density in relaxor ferroelectrics is commonly accompanied with high breakdown strength, which is adverse to the actual dielectric capacitor applications. We demonstrate that such drawback can be effectively resolved by using Sr_0.7Bi_0.2TiO₃ (SBT) to partially replace relaxor ferroelectric 0.76(Bi_0.5Na_0.5)TiO₃-0.24NaNbO₃ (BNT-NN-xSBT). In this study, a high recoverable energy storage density (W_rec∼3.12 J/cm³) and favorable efficiency (η∼75.3 %) are achieved in the BNT-NN-0.1SBT ceramic under a low electric field of 200 kV/cm, which is superior to that of most previously reported dielectric ceramics under the same electric field level. Good temperature stability (25−120 °C), moderate frequency dependence (1−500 Hz), and excellent fatigue resistance (up to 10⁵ cycles) are also realized. More interestingly, the indicated ceramics perform high power density (P_D∼36.40 MW/cm³) and fast discharge time (t_0.9∼0.149 μs) with remarkable temperature endurance. Moreover, of particular significance is that this study offers a feasible guideline to design comprehensive energy storage performance dielectric ceramics for practical applications.     

(Bi0.5Na0.5)TiO3-based relaxor ferroelectrics with simultaneous high energy storage properties and remarkable charge-discharge performances under low working electric fields for dielectric capacitor applications

High energy storage and charge-discharge performances under low electric field are desirable for lead-free dielectric materials because of environmental hazards, the risk of high voltage and the high cost of insulation technology. Herein, lead-free ceramics based on 0.6BNT-0.4Sr_0.775Bi_0.15TiO₃ (BNT-SBT) were designed, which simultaneously achieves a large energy storage density (W_rec~ 2.41 J/cm³) and a high efficiency (η~87.5%) under a low electric field of 190 kV/cm due to enhanced dielectric properties and the relaxation response. Moreover, the energy storage properties of the BNT-SBT ceramic exhibit moderate temperature stability, excellent frequency dependence, and cycling reliability. Furthermore, the charge-discharge performance simultaneously features a high power density (P_D~51.4 MW/cm³), an ultrafast discharge speed (t_0.9–77 ns), and remarkable stability against temperature and cycling. This study exploits a high-efficiency BNT-related ceramics with concurrently high energy storage and charge-discharge performances under low electric fields, which provides great potential in practical dielectric capacitor applications.     

Dielectric properties and relaxor behavior of 0.935(Na0.5Bi0.5)TiO3-0.065BaTiO3 lead free piezoelectric ceramic

Dielectric properties of 0.935(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃ lead free piezoelectric ceramic are studied. The study shows a diffuse phase transition (DPT) characterized by a frequency dispersion of permittivity which is related to cation disorder at A-site. Additionally to this dispersion, this solid solution exhibits relaxor behavior. The mechanism of relaxor behavior was discussed according to Debye, Vogel–Fulcher (V–F) and Power law models and the suitable model was predicted by means of goodness of parameter.     

Enhanced energy storage in temperature stable Bi0.5Na0.5TiO3-modified BaTiO3-Bi(Zn2/3Nb1/3)O3 ceramics

Recently, BaTiO₃-BiMeO₃ ceramics have garnered focused research attention due to their outstanding performance, such as thermal stability, energy efficiency and rapid charge-discharge behavior, however, a lower recoverable energy storage density (W_rec) caused by a relatively low P_max (<30 μC/cm²) mainly hinders practical applications. Herein, the energy density and thermal stability are improved by adding a tertiary component, i.e., Bi_0.5Na_0.5TiO₃, into BaTiO₃-BiMeO₃, resulting in xBi_0.5Na_0.5TiO₃-modified 0.88BaTiO₃-0.12Bi(Zn_2/3Nb_1/3)O₃ ceramics, with x = 0, 0.1, 0.2, 0.3 and 0.4, with superior dielectric properties and eco-friendly impact. Incorporating Bi_0.5Na_0.5TiO₃ with a high saturation polarization and Curie temperature not only significantly enhances P_max of BaTiO₃-Bi(Zn_2/3Nb_1/3)O₃ but also improves Curie temperature of (1-x)[0.88BaTiO₃-0.12Bi(Zn_2/3Nb_1/3)O₃]-xBi_0.5Na_0.5TiO₃ system. Combined with complementary advantages, modified ceramics render a superior energy storage performance (ESP) with a high W_rec of 3.82 J/cm³, efficiency η of 94.4% and prominent temperature tolerance of 25–200 °C at x = 0.3. Moreover, this ceramic exhibit excellent pulse performance, realizing discharge energy storage density W_dis of 2.31 J/cm³ and t_0.9 of 244 ns. Overall, the proposed strategy effectively improved comprehensive properties of BaTiO₃-based ceramics, showing promise in next-generation pulse applications.     

Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3:ZnO relaxor ferroelectric composites with high breakdown electric field and large energy storage properties

0.82[0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃]-0.18K_0.5Na_0.5NbO₃:xZnO (BNT-BT-KNN:xZnO, x?=?0-0.40) relaxor composites were prepared and their electrical properties were investigated. The breakdown electric field increases with increasing ZnO content. For x?=?0 and x?=?0.40 samples, the maximum recoverable energy storage density is 0.74?J/cm³ and 1.03?J/cm³ while the maximum energy storage efficiency is 86.7% and 72.7% under the electric field of 9.0?kV/mm and 14.0?kV/mm, respectively. The recoverable energy storage density and efficiency of the composite vary less than 2.5% from 25?°C to 125?°C, which indicates temperature-insensitive energy storage performance. These results are discussed based on the ZnO-enhanced bulk resistivity and the ZnO-induced local electric field which suppresses the evolution of polar nanoregions.     

Relaxor antiferroelectric-like characteristic boosting enhanced energy storage performance in eco-friendly (Bi0.5Na0.5)TiO3-based ceramics

Ideal relaxor antiferroelectrics (RAFEs) have high field-induced polarization, low remnant polarization and very slim hysteresis, which can generate high recoverable energy storage W_rec and high energy storage efficiency η, thus attracting much attention for energy storage applications. True RAFEs, on the other hand, are extremely rare, and the majority of them contain environmentally hazardous lead. In this work, we use a viscous polymer rolling process to synthesize a novel and eco-friendly 0.65Bi_0.5Na_0.4K_0.1TiO₃-0.35[2/3SrTiO₃-1/3Bi(Mg_2/3Nb_1/3)O₃] (BNKT-ST-BMN) dielectric material, which possesses a very typical RAFE-like characteristic. As a result, this material has a high W_rec of 4.43 J/cm³ and a η of 86% at an electric felid of 290 kV/cm, as well as a high thermal stability of W_rec (>3 J/cm³) over a wide range of 30–140 °C at 250 kV/cm. Our findings suggest that the BNKT-ST-BMN material could be a potential candidate for use in energy storage pulse capacitors.     

Giant comprehensive energy storage performance in Pb-doped Bi0.25Na0.25Sr0.5TiO3 ceramics via multiscale regulation of grain size and relaxation behavior

Developed ceramic capacitors with excellent recoverable energy storage density (W_rec) and efficiency (η) are greatly desired for next-generation pulsed power devices but challenge as well. Herein, outstanding W_rec of 5.2 J/cm³ and η of 82% are achieved in the PbO-doped fine grain Bi_0.25Na_0.25Sr_0.5TiO₃ (BNST-P) based relaxor ferroelectric ceramics. The corresponding mechanism is that A-site Pb-doping increases maximum polarization and breakdown strength, and suppresses remnant polarization simultaneously. Meanwhile, the energy storage property possesses excellent temperature and frequency stability, and the variation of W_rec and η is less than 5% within the range of 25–100 °C and 2–100 Hz. Encouragingly, superior charge-discharge performance with fast discharge speed t_0.9 of 24 ns and high power density P_D of 296 MW/cm³ is obtained. These striking comprehensive results suggest BNST-P ceramics possess potential prospects for applications.     

Strain properties of (1-x)Bi0.5Na0.4K0.1TiO3-xBi(Mg2/3Ta1/3)O3 electroceramics

A ternary solid solution of Bi_0.5Na_0.5TiO₃–Bi_0.5K_0.5TiO₃–Bi(Mg_2/3Ta_1/3)O₃ (BNKT-xBMT) lead-free electroceramics was synthesized by a solid-state reactive sintering technique. The electrostrain, dielectric, and ferroelectric properties as well as the impedance characteristics and the microstructure were systematically assessed. With the increase of BMT, the BNKT-xBMT ceramics gradually transformed from non-ergodic relaxor phase to ergodic relaxor phase, manifested as the ferroelectric-to-relaxor temperature (T_F-R) shifts towards below room temperature. Additionally, the ferroelectric hysteresis curves became pinched, and the strain curve changed from butterfly-shaped into sprout-shaped. At the ergodic relaxor composition of x = 0.04, a large electrostrain value (S = 0.4%; under an electric field of 60 kV/cm, d₃₃* = 632 pm/V) was achieved, which is mainly attributed to the electric-field-induced transition from the ergodic relaxor phase to the ferroelectric phase.     

Influence of BaSnO3 additive on the energy storage properties of Na0.5Bi0.5TiO3-based relaxor ferroelectrics

(1-x)NBT-xBSN (0.1?≤?x?≤?0.35) ceramics were prepared by solid state methods and their energy storage properties and high-temperature capacitor applications were systematically investigated. All samples showed a perovskite structure and the structure transformed to lower symmetry orthorhombic phase (x?≥?0.1) from rhombohedral phase (x?<?0.1) to with the addition of BSN. The more addition content of BSN significantly decreases phase transition temperature T_m of NBT ceramics. The x?=?0.25 sample exhibits a stable relative permittivity of 1605?±?15% in a broad temperature range of 38?°C to 319?°C. With increasing BSN concentration, the slope of the P-E loops and the energy loss gradually decreases. When x?=?0.25, a high breakdown strength of 190?kV/cm and the maximum discharge energy density of 1.91?J/cm³ were obtained, of which the energy efficiency was as high as 86.4%. Thus, it was believed that our work could provide a significant guidance for designing the new system for energy storage.     

Structure,dielectric properties of novel Ba(Zr,Ti)O3 based ceramics for energy storage application

(1-x) Ba(Zr_0.2Ti_0.8)O₃-x Na_0.5Bi_0.5TiO₃ (x = 0, 10, 20 30, 40, 50 mol%) (BZTN) ceramics are prepared by the traditional solid phase method. All BZTN ceramics exhibit a pseudo-cubic BZT based perovskite structure. Both the average grain size and the relaxor ferroelectricity of BZTN ceramics gradually increase with increasing NBT content. The W_rec of 3.22 J/cm³ and η of 91.2% is obtained for the BZTN40 ceramic at 241 kV/cm. BZTN40 ceramic also exhibits good temperature stability from room temperature to 150 °C and frequency stability from 1 Hz to 100 Hz. A P_D of 0.621 J/cm³ and a t_0.9 of 82 ns is obtained for the BZTN40 ceramic at 120 kV/cm. BZTN ceramics show application potential in energy storage and pulse power capacitors.     

Realizing excellent energy storage properties in Na0.5Bi0.5TiO3-based lead-free relaxor ferroelectrics

Development of lead-free dielectric capacitors with high recoverable energy storage density (W_rec), large energy storage efficiency (η), and wide usage temperature range are in high demanded for pulse power systems. Herein, we realized the enhancement of energy storage properties [high W_rec = 3.76 J/cm³, large η = 78.80 %, and broad operating temperature range (20?180 °C)] in lead-free Na_0.5Bi_0.5TiO₃ (BNT)-based relaxor ferroelectrics via component regulation. Excellent energy storage properties mainly originate from suppressing early polarization saturation and improving dielectric breakdown strength (E_b). Domain evolution on the nanoscale offers robust support to suppression of early polarization saturation. The enhancement of E_b can be derived from the contribution of the Mg-rich phase, which is also corroborative via first-principles calculation on basis of density functional theory (DFT). We believe that these findings in this work may provide a practicable guideline to build new lead-free ceramics for electrical energy storage applications.     

Achieving excellent energy storage properties of Na0.5Bi0.5TiO3 - based ceramics by using a two-step strategy involving phase and polarization modification

Na_0.5Bi_0.5TiO₃-based ceramic specimens have been extensively investigated as ferroelectric materials. After being doped with CaTiO₃, the resulting Na_0.5Bi_0.5TiO₃-based ceramics exhibit relaxor characteristics, and improved energy storage density and efficiency. Based on these above results, CeO₂ was further employed to modify the polarization of the 0.85Na_0.5Bi_0.5TiO₃-0.15CaTiO₃ matrix ceramic to achieve better energy storage performance. The effective energy storage density was enhanced from 1.93 to 2.53 J/cm³ by using the appropriate doping concentration of CeO₂. Grain refinement effect can effectively enhance the electric-field strength from approximately 190 to 230 kV/cm. In particular, when doped with 2% CeO₂, the energy storage efficiency of the sample was maintained at approximately 90% at 30 °C-150 °C and at approximately 80% in the frequency range of 0.2–200 Hz. This combination has very excellent temperature stability and frequency stability, making it a promising candidate for energy storage applications.     

Antiferroelectric-like properties in MgO-modified 0.775Na0.5Bi0.5TiO3-0.225BaSnO3 ceramics for high power energy storage

Antiferroelectric-like 0.775NBT-0.225BSN-x wt%MgO ceramics have been prepared by solid state methods. The second phase of MgO was found in grain boundary surroundings with fine grains, which has been confirmed by EDS mapping and XRD results. Frequency dispersion of x?=?0 sample was replaced by diffuse phase transition of MgO-doped samples. Antiferroelectric-like properties were firstly observed in MgO modified ceramics. The evolution of antiferroelectric-like /ferroelectric transitions was demonstrated by I-E curves. With increasing MgO concentration, the BDS and E_F-E_B gradually increase. The leakage current can be reduced by suitable amount of MgO addition. When the doping content is 5?wt.%, the maximum discharge energy density of 2.13?J/cm³ at an electric field of 215?kV/cm was achieved. Detailed analysis can be found in the study.     

Enhanced energy storage properties and stability in (Pb0.895La0.07)(ZrxTi1-x)O3 antiferroelectric ceramics

Recently, the (Pb,La)(Zr,Ti)O₃ antiferroelectric materials with slim-and-slanted double hysteresis loops have been widely drawn in the application of advanced pulsed power capacitors due to its low strain characteristic. In this work, the energy storage properties of (Pb_0.895La_0.07)(Zr_xTi_1-x)O₃ ceramics with different Zr contents are researched thoroughly because the substitution of Ti⁴⁺ by Zr⁴⁺ can reduce the tolerance factor t, enhancing the antiferroelectricity. The polarization-electric field hysteresis loops of the PLZT ceramics become slimmer with increasing Zr content. The highest recoverable energy storage density (W_re) of 3.38 J/cm³ and ultrahigh energy efficiency (η) of 86.5% are achieved in (Pb_0.895La_0.07)(Zr_0.9Ti_0.1)O₃ ceramic. The (Pb_0.895La_0.07)(Zr_0.9Ti_0.1)O₃ ceramic also hold fairly thermal stability (relative variation of W_re is less than 28% over 30 °C-120 °C), excellent frequency stability (10–1000 Hz) and good fatigue endurance. These results demonstrate that the (Pb_0.895La_0.07)(Zr_0.9Ti_0.1)O₃ ceramic can be a desirable material for dielectric energy storage capacitors, especially for pulse power technology.     

Designing novel lead-free NaNbO3-based ceramic with superior comprehensive energy storage and discharge properties for dielectric capacitor applications via relaxor strategy

There are urgent demands for high performance capacitors with superior energy storage density and discharge performances. In this work, novel NaNbO₃-based lead-free ceramics (0.91NaNbO₃-0.09Bi(Zn_0.5Ti_0.5)O₃) with high energy storage capability, high power density and fast discharge speed were designed and prepared. Bi(Zn_0.5Ti_0.5)O₃ was chosen for the purpose to reduce the remnant polarization and improve the induced polarization. Consequently, a large stored energy storage density (W_s˜ 3.51 J/cm³) and high recoverable energy storage density (W_rec˜ 2.20 J/cm³) were obtained in 0.91NaNbO₃-0.09Bi(Zn_0.5Ti_0.5)O₃ ceramic under a high breakdown strength of 250 kV/cm, with excellent thermal stability in the range of 20–120 °C. More importantly, the investigated ceramics exhibited high power density (P_D˜ 20 MW/cm³) and ultrafast discharge rate (t_0.9˜ 0.25 μs), demonstrating potential application in pulse powehr systems. This work provides an effective means of achieving excellent energy storage and discharge performances in NaNbO₃-based ceramics for application in dielectric capacitors.     

Tailoring structural and electrical properties of A-site non-stoichiometric Na0.5Bi0.5TiO3 ceramic at different sintering temperature

Na/Bi stoichiometry plays crucial role in determining various properties of sodium bismuth titanate-based system. In this work, we have synthesised lead free (Na_0.5Bi_0.5)_1+x TiO₃ (x?=?0, 0.02 and 0.05) ceramics by sol-gel method and systematically presented structural, dielectric and ferroelectric properties at different sintering temperature. Single phase perovskite structure with rhombohedral symmetry (R3c) is obtained for all compositions from low (850°C) to maximum (1150°C) sintering temperature. The shifting of x-ray diffraction peaks and characteristic perovskite metal-oxide vibrational band (～627?cm^?1) in Fourier Transform Infra-red spectra suggests compression or expansion of crystal lattice with Na/Bi non-stoichiometry. Excess of Na/Bi comprises dense crystal growth as compared to pure Na_0.5Bi_0.5TiO₃ composition suggesting compensation of volatile elements loss during heat treatment whose impact has also been observed in dielectric as well as ferroelectric properties. It is observed that Na_0.51Bi_0.51TiO₃ sample with x?=?0.02 exhibits better structural, dielectric and ferroelectric properties in whole range of sintering temperature.