Enhanced optical transmittance and energy-storage performance in NaNbO3-modified Bi0.5Na0.5TiO3 ceramics

Dielectric ceramics with both excellent energy storage and optical transmittance have attracted much attention in recent years. However, the transparent Pb-free energy-storage ceramics were rare reported. In this work, we prepared transparent relaxor ferroelectric ceramics (1 − x)Bi_0.5Na_0.5TiO₃–xNaNbO₃ (BNT–xNN) by conventional solid-state reaction method. We find the NN-doping can enhance the polarization and breakdown strength of BNT by suppressing the grain growth and restrained the reduction of Ti⁴⁺ to Ti³⁺. As a result, a high recoverable energy-storage density of 5.14 J/cm³ and its energy efficiency of 79.65% are achieved in BNT–0.5NN ceramic at 286 kV/cm. Furthermore, NN-doping can promote the densification to improve the optical transmittance of BNT, rising from ∼26% (x = 0.2) to ∼32% (x = 0.5) in the visible light region. These characteristics demonstrate the potential application of BNT–xNN as transparent energy-storage dielectric ceramics.     

High energy storage and ultrafast discharge in NaNbO3-based lead-free dielectric capacitors via a relaxor strategy

Dielectric capacitors with decent energy storage and fast charge-discharge performances are essential in advanced pulsed power systems. In this study, novel ceramics (1-x)NaNbO₃-xBi(Ni_2/3Nb_1/3)O₃(xBNN, x = 0.05, 0.1, 0.15 and 0.20) with high energy storage capability, large power density and ultrafast discharge speed were designed and prepared. The impedance analysis proves that the introducing an appropriate amount of Bi(Ni_0·5Nb_0.5)O₃ boosts the insulation ability, thus obtaining a high breakdown strength (E_b) of 440 kV/cm in xBNN ceramics. A high energy storage density (W_total) of 4.09 J/cm³, recoverable energy storage density (W_rec) of 3.31 J/cm³, and efficiency (η) of 80.9% were attained in the 0.15BNN ceramics. Furthermore, frequency and temperature stability (fluctuations of W_rec ≤ 0.4% over 5–100 Hz and W_rec ≤ 12.3% over 20–120 °C) were also observed. The 0.15BNN ceramics exhibited a large power density (19 MW/cm³) and ultrafast discharge time (~37 ns) over the range of ambient temperature to 120 °C. These enhanced performances may be attributed to the improved breakdown strength and relaxor behavior through the incorporation of BNN. In conclusion, these findings indicate that 0.15BNN ceramics may serve as promising materials for pulsed power systems.     

Synthesis and characterizations of BNT–BT and BNT–BT–KNN ceramics for actuator and energy storage applications

Dielectric and ferroelectric properties of 0.93Bi_0.5Na_0.5TiO₃–0.07BaTiO₃ (BNT–BT) and 0.93Bi_0.5Na_0.5TiO₃–0.06BaTiO₃–0.01K_0.5Na_0.5NbO₃ (BNT–BT–KNN) ceramics were studied in detail. An XRD analysis confirmed the single perovskite phase formation in both the samples. Room temperature (RT) dielectric constant (ε_r) ~1020 and 1370, respectively at 1 kHz frequency were obtained in the BNT–BT and BNT–BT–KNN ceramics. Temperature dependent dielectric and the polarization vs. electric field (P–E) studies confirmed the coexistence of ferroelectric (FE) and anti-ferroelectric (AFE) phases in the BNT–BT and BNT–BT–KNN ceramics. Substitution of KNN into the BNT–BT system decreased the remnant polarization, coercive field and the maximum strain percentage. The energy storage density values ~0.485 J/cm³ and 0.598 J/cm³ were obtained in the BNT–BT and BNT–BT–KNN ceramics, respectively. High induced strain% in the BNT–BT ceramics and the high energy storage density in the BNT–BT–KNN ceramics suggested about the usefulness of these systems for the actuator and the energy storage applications, respectively.     

Effect of Sr(Zn1/3Nb2/3)O3 modification on the energy storage performance of BaTiO3 ceramics

Lead-free (1-x)BaTiO₃-xSr(Zn_1/3Nb_2/3)O₃ (abbreviated as BT-xSZN, x = 0–0.08) relaxor ferroelectric ceramics were prepared using the traditional solid phase technology, and the effects of SZN modification on their phase structures, microstructures, dielectric performance, ferroelectricity and energy storage performance were studied in detail. A pure perovskite phase was observed in the BT-xSZN ceramics. The BT-based ceramics modified by SZN exhibited refined grain size. As the SZN content was increased, the breakdown strength initially increased and then decreased, and the ferroelectric loops gradually became ‘slim’. The BT-xSZN (x = 0.07) ceramics demonstrated a favourable energy storage performance with high recoverable energy density (W_rec = ~1.45 J/cm³) and energy storage efficiency (η = ~83.12%) at 260 kV/cm. Results indicate that the energy storage performance of BaTiO₃ ceramics modified by SZN can be remarkably improved, widening their applications in energy storage at low temperatures.     

SrTiO3-modified Bi0.5Na0.47Li0.03Ti0.99Sn0.01O3 relaxor ferroelectric ceramics with high energy storage performance

(1 − x)Bi_0.5Na_0.47Li_0.03Ti_0.99Sn_0.01O₃–xSrTiO₃ (BNLST–xST) lead-free ceramics were synthesized by traditional solid phase sintering. When x = 0.4, the ceramic achieves a high energy storage density W_rec of 3.78 J/cm³ as well as a superior efficiency η of 90.3% under 360 kV/cm. The charge–discharge curves related to temperature and cycle show that the 0.6BNLST–0.4ST sample has good temperature stability (20–180°C) and cycling reliability (variation of W_D < 5%). Moreover, a fast discharge rate (t_0.9 = 0.219 μs) and a large discharge energy density (W_D = 1.89 J/cm³) are achieved at 220 kV/cm. The results show that BNLST–xST energy storage ceramics are promising materials for devices with pulsed power capacitor.     

Enhanced energy storage performances of Bi(Ni1/2Sb2/3)O3 added NaNbO3 relaxor ferroelectric ceramics

In the development of dielectric ceramic materials, the requirements of miniaturization and integration are becoming increasingly prominent. How to obtain greater capacitance in a smaller volume is one of the important pursuits. In this paper, lead-free (1-x)NaNbO₃-xBi(Ni_1/2Sb_2/3)O₃(xBNS) with high recoverable energy storage density (W_rec) and relatively high energy storage efficiency(η) were prepared by a solid state sintering method. Bi(Ni_1/2Sb_2/3)O₃ was introduced into the Sodium niobate ceramics(NN)-based ceramics to reduce the sintering temperature and increase the maximum breakdown field strength (E_b). Finally, 0.15BNS achieved a high E_b of 460 kV/cm, W_rec of 3.7 J/cm³ and η of 77%. In addition, the sample maintained excellent stability in the frequency range of 1–120 Hz. And the 0.15BNS ceramics also exhibited high power density (P_D = 36.4 MW/cm³), large current density (C_D = 520.8 A/cm²) and relatively fast charge-discharge rate (t_0.9 = 1050 ns). These results demonstrate the potential application value of xBNS ceramics in energy storage capacitors.     

Ultrahigh energy storage density and efficiency in PLZST antiferroelectric ceramics via multiple optimization strategy

Antiferroelectric (AFE) ceramic materials possess ultrahigh energy storage density due to their unique double hysteresis characteristics, and PbZrO₃ is one of the promising systems, but previous materials still suffer from the problem that energy storage density and energy storage efficiency can hardly be improved synergistically. In this work, a multiple optimization strategy is proposed to substantially improve the energy storage efficiency while maintaining the high energy storage density of PZ-based AFE ceramics. Sr²⁺-doped (Pb_0.90La_0.02Sr_0.08)[(Zr_0.5Sn_0.5)_0.9Ti_0.1]_0.995O₃ ceramics was successfully synthesized by viscous polymer process and two-step sintering. The diffuse phase transition constructed in this ceramic depleted the threshold electric field hysteresis and current while the breakdown field strength was increased again. An ultrahigh recoverable energy density (W_rec) of 7.9 J/cm³ with a high energy storage efficiency (η) of 96.4 % are achieved synchronously at an electric field of 510 kV/cm. Moreover, the AFE ceramics possess remarkable discharge energy storage properties with a high discharge energy density (W_d) of 7.4 J/cm³ and a large power density (P_d) of 224 MW/cm³.     

Enhanced energy storage performance of eco-friendly BNT-based relaxor ferroelectric ceramics via polarization mismatch-reestablishment and viscous polymer process

In this work, we synthesized a novel and eco-friendly relaxor ferroelectric system, i.e., (1?x)(0.8Bi_0.5Na_0.4K_0.1TiO₃-0.2SrTiO₃)-xNaNbO₃ (BS-xNN) ceramics with x = 0.1–0.4 based on a solid state reaction technique. The structural, microstructural, dielectric as well as ferroelectric characteristics of BS-xNN ceramics were comprehensively examined. According to our findings, the Ti–O coupling reduces as the NN content increases, while the Nb–O coupling strengthens, leading in a nano-scale polarization mismatch-reestablishment process that enhances energy storage performance. Because of the reduction in thickness and porosity, the viscous polymer process significantly increases the breakdown strength of ceramic samples. More crucially, at 260 kV/cm, 0.6BS-0.4NN ceramics have an ultrahigh recoverable energy storage density W_rec of 4.44 J/cm³ and a high energy storage efficiency η of 81.8%. Furthermore, thermal stability of energy storage performance is also identified across a wide temperature range of 30 °C from 140 °C at 215 kV/cm. The higher performance of energy storage not only indicates the feasibility of our technique, but also serves as a model for the manufacturing of high-quality dielectric ceramics with a wide range of industrial applications.     

High recoverable energy storage density in nominal (0.67-x)BiFeO3-0.33BaTiO3-xBaBi2Nb2O9 lead-free composite ceramics

A series of novel lead-free energy storage ceramics, (0.67-x)BiFeO₃-0.33BaTiO₃-xBaBi₂Nb₂O₉ (BF-BT-xBBN), were fabricated by traditional solid-state reaction, where bismuth layer-structured BaBiNb₂O₉ was incorporated into perovskite-structured BiFeO₃–BaTiO₃ ceramic as an additive. The addition of BaBi₂Nb₂O₉ increased the relaxor behavior and breakdown strength of BF-BT ceramics due to the formation of polar nanoregionals (PNRs), inducing enhanced energy storage performance. The composite ceramics, with x = 0.08, showed a large recoverable energy density (W_rec) of 3.08 J/cm³ and an outstanding energy storage efficiency (η) of 85.57% under an applied electric field of 230 kV/cm. Moreover, the composite ceramics exhibited excellent thermal stability and high stability toward different frequencies in a temperature range of 20–100 °C and a frequency range of 0.1–1500 Hz. These results demonstrate great potential of novel BF-BT-xBBN composite ceramics for next-generation energy storage applications.     

Realizing high energy density and superior charge-discharge characteristics in NN-10BT-based ceramics

The low recoverable energy storage density (W_rec) of bulk ceramics has long limited their miniaturization and lightweight development. Here, we designed the (1-x)(0.90NaNbO₃-0.10BaTiO₃)-xNa_0.2Bi_0.4La_0.2TiO₃ (NN-10BT-xNBLT) ceramics. With the introduction of NBLT, the dielectric breakdown strength (BDS) of NN-10BT-based ceramics increased from 174.8 kV/cm to 289.1 kV/cm. A promising finding is that the NN-10BT-15NBLT ceramic has an ultrahigh energy storage density W of 3.42 J/cm³ and a large energy storage efficiency η of 78.9%, as well as excellent frequency and thermal stability. The NN-10BT-15NBLT ceramic, on the other hand, has an outstanding current density C_D of 1021.21 A/cm² together with a high power density P_D of 102.12 MW/cm³ at 200 kV/cm. Most importantly, the variation of charge-discharge properties (C_D and P_D) is only ?7.8% after 10⁴ cycles, suggesting that the capacitor has potential practical application significance.     

Energy storage and discharge performance for (1−x)BaSrTiO3−xBi(Zn1/2Ti1/2)O3 ceramics

Although lead-free dielectric ceramics have been widely studied to obtain excellent dielectric properties and good energy storage properties, the primary challenge of low energy storage density has not yet been resolved. Here, we introduce the concept of crossover relaxor ferroelectrics, which represent a state intermediate between normal ferroelectrics and relaxor ferroelectrics, as a solution to address the issue of low energy density. The (1−x)BaSrTiO₃−xBi(Zn_1/2Ti_1/2)O₃ (x = 0,.05, .1, .15, .2) ceramics were prepared by a solid-state method. Remarkably, 0.85BST–0.15BZT ceramics achieved a high recoverable energy density (W_rec) of 2.18 J/cm³ under an electric field of 240 kV/cm. BST–BZT materials exhibit substantial recoverable energy density, high breakdown strength, and superior energy efficiency, positioning them as a promising alternative to meet the diverse demands of high-power applications.     

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.     

Improved dielectric strength and energy storage density in Ba6−3xLa8+2xTi18O54 (x = 0.5, 2/3, and 0.75) ceramics

Dielectric strength and energy storage density in Ba_6−3xLa_8+2xTi₁₈O₅₄ (x = 0.5, 2/3, and 0.75) ceramics were investigated as functions of composition and microstructure. With increasing x, although the dielectric constant decreased from 113 to 102, the energy storage density increased from 2.3 J/cm³ to 3.2 J/cm³ due to the increased dielectric strength for ceramics prepared by conventional sintering. The energy storage was further improved to 4.2 J/cm³ in ceramics prepared by spark plasma sintering under an electric field of 1058 kV/cm. Both dielectric strength and energy storage density in the present ceramics indicated the strong processing and microstructure dependence. The optimum dielectric strength and energy storage density were achieved in the dense ceramics with fine grains, while both dielectric strength and energy storage density decreased in the ceramics with coarse columnar grains.     

Enhanced energy storage performance and temperature stability achieved by a synergic effect in Nd3+/Ga3+ co-doped (Na0.5Bi0.5)TiO3 -based ceramics

(1-x)(0.75(Na_0.5Bi_0.5)TiO₃-0.25SrTiO₃)-xNdGaO₃ ceramics (NBST-xNG, x = 0–0.06) were fabricated through a solid-state reaction method. High-valent Nd³⁺ ions enter the perovskite A-site to occupy Bi vacancies resulting from the volatilization of Bi, inhibiting the formation of oxygen vacancies and contributing to an enhanced breakdown electric field (E_b). Low-valent Ga³⁺ ions enter the B-site to substitute for Ti⁴⁺ ions, resulting in the formation of random electric fields (REFs) at the B-site due to co-occupying hetero-valence ions of Ga³⁺/Ti⁴⁺, which significantly reduces ferroelectric hysteresis. Therefore, a synergic effect of A- and B-sites co-doping was realized in NBST-xNG ceramics. Benefitting from this synergic effect, an enhanced recoverable energy storage density (W_rec) of 2.88 J/cm³ and an efficiency (η) of 83% are simultaneously obtained in NBST-0.04NG ceramics under a moderate electric field (E) of 200 kV/cm. Compared with most NBT-based ceramics, the values of (η vs W_rec/E²) for NBST-0.04NG ceramics show an obvious advantage, indicating excellent potential for application as an energy storage material. Moreover, W_rec and η of NBST-0.04NG ceramics exhibit excellent temperature stability from 30 °C to 200 °C due to the enhanced correlation strength of polar nanoregions (PNRs) and local structural stability. This work provides a potential strategy to improve the energy storage performance of NBT-based ceramics via the synergic effect of A- and B-site co-doping.     

Enhanced energy storage properties of Bi(Ni2/3Nb1/6Ta1/6)O3–NaNbO3 solid solution lead-free ceramics

Sodium niobate energy storage ceramics with good environmental performance are widely used in electric power conversion and pulse power system, large energy storage density and high efficiency, huge power density and charge and discharge faster. In this work, (1-x)NaNbO₃-xBi(Ni_2/3Nb_1/6Ta_1/6)O₃ [(1-x)NN-xBNNT] (0.12 ≤ x ≤ 0.18) ceramics system were prepared by solid state reaction method. By introducing Bi(Ni_2/3Nb_1/6Ta_1/6)O₃ (BNNT), a relaxation strategy was constructed, which significantly improved the energy storage properties of NaNbO₃ (NN) based ceramics. Finally, comparatively high recoverable energy density (W_rec) of 3.43 J/cm³ and large energy storage efficiency (η) of 83.3% were obtained in 0.86NN-0.14BNNT ceramics. Besides discharge energy density (W_d) of 0.69 J/cm³, ultra fast charge-discharge rate (t_0.9) of 55 ns, the power density (P_D) of 70.66 MW/cm³ and the current density (C_D) of 883.23 A/cm² were also observed in ceramic.     

Achieving outstanding temperature stability in KNN-based lead-free ceramics for energy storage behavior

Lead-free ceramics with prominent energy storage properties are identified as the most potential materials accessed in the dielectric capacitors. Nevertheless, high recoverable energy storage density (W_rec), large energy storage efficiency (η) and preferable temperature stability can hardly be met simultaneously. The Bi(Zn_2/3Ta_1/3)O₃ and NaNbO₃ components are doped in KNN ceramics to substantiate the reliability of this tactic. A high recoverable energy density (W_rec) of ～ 4.55 J/cm³ and a large energy storage efficiency (η) of ～ 87.8% are acquired under the dielectric breakdown strength (DBS) of ～ 375 kV/cm, along with a splendid thermal stability (W_rec variation: ～ 2.3%, η variation: ～ 4.9%) within the temperature range of 20 ℃? 120 ℃. This article demonstrates that the KNN-based ceramics integrate high energy storage properties and outstanding temperature stability at the same time, which broadens the application fields of pulse power systems.     

High recoverable energy storage density and large energy efficiency simultaneously achieved in BaTiO3–Bi(Zn1/2Zr1/2)O3 relaxor ferroelectrics

Relaxor ferroelectrics have attracted much attention as electric energy storage materials for intermittent energy storage because of their high saturated polarization, near-zero remnant polarizations, and considerable dielectric breakdown strength (BDS). Despite the numerous efforts, the dielectric energy storage performance of relaxor ferroelectric ceramics is incomplete or unsatisfactory. The enhancement of recoverable energy storage density W_rec usually accompanies with the sacrifice of discharge-to-charge energy efficiency η; therefore, it is an important issue to achieve high recoverable W_rec and large efficiency η simultaneously. In this work, the (1-x)BaTiO₃-xBi(Zn_1/2Zr_1/2)O₃ (abbreviated as BT-100xBZZ, 0 ≤ x ≤ 0.20) ferroelectric ceramics were prepared using the conventional solid-state reaction method. The phase structure, microstructural morphology, dielectric and ferroelectric properties, relaxation behaviors, and energy storage properties of BT-BZZ ceramics were investigated in detail. X-ray powder diffraction, dielectric spectra, and ferroelectric properties confirm the transformation of tetragonal phase for normal ferroelectrics (BT) to pseudo-cubic phase for relaxor ferroelectrics (BT-8BZZ). A high recoverable energy storage density W_rec of 2.47 J/cm³ and a large energy efficiency η of 94.4% are simultaneously achieved in the composition of BT-12BZZ, which presents typical weakly coupled relaxor ferroelectric characteristics, with an activation energy E_a of 0.21 eV and a freezing temperature T_f of 139.7 K. Such excellent energy storage performance suggests that relaxor ferroelectric BT-12BZZ ceramics are promising dielectric energy storage materials for high-power pulsed capacitors.     

Excellent energy storage performance of NaNbO3-based antiferroelectric ceramics with ultrafast charge/discharge rate

Dielectric capacitors have drawn increasing attention due to their fast charge/discharge rates and high power density. Among all known ceramic dielectric materials, antiferroelectrics are more attractive for their unique double ferroelectric hysteresis loops and higher energy densities. Here, a series of antiferroelectric ceramics x(0.95Bi_0.5Na_0.5TiO₃-0.05SrZrO₃)-(1-x)NaNbO₃ (xBNTSZ-(1-x)NN, x = 0.23, 0.30, 0.35, 0.50) have been prepared. By stabilizing the antiferroelectric phase and postponing the critical electric field of the antiferroelectric-ferroelectric phase transition, an impressive discharge energy storage density of 4.08 J/cm³ at a breakdown strength of 370 kV/cm was achieved for the 0.35BNTSZ-0.65 N N. A superior comprehensive performance for the 0.50BNTSZ-0.50 N N ceramic with a discharge energy storage density (W_dis) of 3.78 J/cm³ and an efficiency of 86 % at an electric field strength of 320 kV/cm along with excellent frequency, temperature, and fatigue stabilities (fluctuations of W_dis≤±5% within 0.01∼100 Hz, W_dis≤10 % over 20∼140 °C, and W_dis≤1% over 10⁶ cycle numbers) is realized. Furthermore, 0.50BNTSZ-0.50 N N ceramics simultaneously exhibit a high current density (622.5 A/cm²), high power density (112 MW/cm³), and fast discharge rate (t = 47 ns), all of which make it an excellent candidate for the pulsed power devices.     

(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.     

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.