Gradient-Structured Ceramics with High Energy Storage Performance and Excellent Stability

Owing to the high power density, eco-friendly, and outstanding stability, the lead-free ceramics have attracted great interest in the fields of pulsed power systems. Nevertheless, the low energy storage density of such ceramics is undoubtedly a severe problem in practical applications. To overcome this limitation, the lead-free ceramics with gradient structures are designed and fabricated using the tape-casting method herein. By optimizing the composition and distribution of the gradient-structured ceramics, the energy storage density, and efficiency can be improved simultaneously. Under a moderate electric field of 320 kV cm⁻¹, the value of recoverable energy storage density (W_rec) is higher than 4 J cm⁻³, and the energy storage efficiency (η) is of ≥88% for 20-5-20 and 20-10-20. Furthermore, the gradient-structured ceramics of 20-10-0-10-20 and 20-15-0-15-20 possess high applied electric field, large maximum polarization, and small remnant polarization, which give rise to ultrahigh W_rec and η on the order of ≈6.5 J cm⁻³ and 89–90%, respectively. In addition, the energy storage density and efficiency also exhibit excellent stability over a broad range of frequencies, temperatures, and cycling numbers. This work provides an effective strategy for improving the energy storage capability of eco-friendly ceramics.     

Superior Energy Storage Properties and Optical Transparency in K0.5Na0.5NbO3-Based Dielectric Ceramics via Multiple Synergistic Strategies

Eco-friendly transparent dielectric ceramics with superior energy storage properties are highly desirable in various transparent energy-storage electronic devices, ranging from advanced transparent pulse capacitors to electro-optical multifunctional devices. However, the collaborative improvement of energy storage properties and optical transparency in KNN-based ceramics still remains challenging. To address this issue, multiple synergistic strategies are proposed, such as refining the grain size, introducing polar nanoregions, and inducing a high-symmetry phase structure. Accordingly, outstanding energy storage density (W_total ≈7.5 J cm⁻³, W_rec ≈5.3 J cm⁻³) and optical transmittance (≈76% at 1600 nm, ≈62% at 780 nm) are simultaneously realized in the 0.94(K_0.5Na_0.5)NbO₃-0.06Sr_0.7La_0.2ZrO₃ ceramic, together with satisfactory charge-discharge performances (discharge energy density: ≈2.7 J cm⁻³, power density: ≈243 MW cm⁻³, discharge rate: ≈76 ns), surpassing previously reported KNN-based transparent ceramics. Piezoresponse force microscopy and transmission electron microscopy revealed that this excellent performance can be attributed to the nanoscale domain and submicron-scale grain size. The significant improvement in the optical transparency and energy storage properties of the materials resulted in the widening of the application prospects of the materials.     

Delayed Polarization Saturation Induced Superior Energy Storage Capability of BiFeO3-Based Ceramics Via Introduction of Non-Isovalent Ions

Electrostatic capacitors are emerging as a highly promising technology for large-scale energy storage applications. However, it remains a significant challenge to improve their energy densities. Here, an effective strategy of introducing non-isovalent ions into the BiFeO₃-based (BFO) ceramic to improve energy storage capability via delaying polarization saturation is demonstrated. Accordingly, an ultra-high energy density of up to 7.4 J cm⁻³ and high efficiency ≈ 81% at 680 kV m⁻¹ are realized, which is one of the best energy storage performances recorded for BFO-based ceramics. The outstanding comprehensive energy storage performance is attributed to inhibiting the polarization hysteresis resulting from generation ergodic relaxor zone and random field, and generating highly-delayed polarization saturation with continuously-increased polarization magnitudes with the electric field of supercritical evolution. The contributions demonstrate that delaying the polarization saturation is a consideration for designing the next generation of lead-free dielectric materials with ultra-high energy storage performance.     

Lead-Free Relaxor Ferroelectric Ceramics with Ultrahigh Energy Storage Densities via Polymorphic Polar Nanoregions Design

One of the long-standing challenges of current lead-free energy storage ceramics for capacitors is how to improve their comprehensive energy storage properties effectively, that is, to achieve a synergistic improvement in the breakdown strength (E_b) and the difference between maximum polarization (P_max) and remnant polarization (P_r), making them comparable to those of lead-based capacitor materials. Here, a polymorphic polar nanoregions (PNRs) structural design by first introducing 0.06 mol BaTiO₃ into Bi_0.5Na_0.5TiO₃ is proposed to construct the morphotropic phase boundary with coexisting structures of micrometer-size domains and polymorphic nanodomains, enhance the electric field-induced polarization response (increase P_max). Then Sr(Al_0.5Ta_0.5)O₃ (SAT)-doped 0.94 Bi_0.5Na_0.5TiO₃-0.06BaTiO₃ (BNBT) energy storage ceramics with polymorphic PNRs structures are synthesized following the guidance of phase-field simulation and rational composition design (decrease P_r). Finally, a large recoverable energy density (W_rec) of 8.33 J cm⁻³ and a high energy efficiency (η) of 90.8% under 555 kV cm⁻¹ are obtained in the 0.85BNBT-0.15SAT ceramic prepared by repeated rolling process method (enhance E_b), superior to most practical lead-free competitors increased consideration of the stability of temperature (a variation <±6.2%) and frequency (W_rec > 5.0  cm⁻³, η > 90%) at 400 kV cm⁻¹. This strategy provides a new conception for the design of other-based multifunctional energy storage dielectrics.     

High-Energy Storage Density and Efficiency of the xBi(Mg2/3Nb1/3)O3-(1 − x)(Ba0.8Sr0.2)TiO3 (0.08 ≤ x ≤ 0.14) Lead-Free Perovskite Structured Ceramics

The compounds xBi(Mg_2/3Nb_1/3)O₃-(1 − x)(Ba_0.8Sr_0.2)TiO₃ (xBMN-(1 − x)BST, 0.08 ≤ x ≤ 0.14) are prepared via the traditional solid-state reaction method and the ceramics are well densified in the sintering temperature range of 1280–1330 °C. X-ray diffraction analysis shows that all the ceramics crystallize into perovskite structure. Proper amounts of BMN additions can effectively reduce grain sizes of the xBMN-(1 − x)BST ceramics, resulting in more uniform microstructures. Accordingly, breakdown strength E_b is improved and a maximum value 250 kV cm⁻¹ is obtained in ceramic with x = 0.10. Meanwhile, recoverable energy storage density W_rec of the 0.1BMN-0.9BST ceramics reaches 2.03 J cm⁻³, and energy storage efficiency (η) is 96.8%. When the operating temperature increases to 150 °C, the W_rec and η values are about 1.02 J cm⁻³ under 150 kV cm⁻¹ and 89.8%, respectively.     

Enhanced Crystallinity,Dielectric, and Energy Harvesting Performances of Surface‐Treated Barium Titanate Hollow Nanospheres/PVDF Nanocomposites

Enhancement of the energy harvesting performance and dielectric constants of poly(vinylidene fluoride) (PVDF)‐based capacitors is realized by incorporating 16 wt% of surface‐treated BaTiO₃ hollow nanospheres (HNSs) in comparison with the pristine PVDF. The fabricated BaTiO₃ HNSs with particle sizes of ≈20 nm and BET surface area of 297 m² g⁻¹ are treated by three different surface modifiers. The changes in crystallinity of the PVDF containing the surface‐treated BaTiO₃ HNSs are induced by both enlarged surface areas and increased surface functionality of the HNSs. Effects of such surface functionalities on the crystalline, dielectric, and energy harvesting performances of the nanocomposites are systematically investigated to identify the optimal surface modifier to enhance the energy density of the nanocomposites. Consequently, these changes in crystallinity lead to higher dielectric constants (ε′ ≈ 109.6) and energy density (U_e ≈ 21.7 J cm⁻³) with highly retained breakdown strength (E = 3.81 × 10³ kV cm⁻¹) compared to pristine PVDF (ε′ ≈ 11.6 and U_e ≈ 2.16 J cm⁻³ at 3.98 × 10³ kV cm⁻¹), indicating their potential as high energy density capacitors.     

Giant Energy Storage Density with Antiferroelectric-Like Properties in BNT-Based Ceramics via Phase Structure Engineering

Driven by the information industry, advanced electronic devices require dielectric materials which combine both excellent energy storage properties and high temperature stability. These requirements hold the most promise for ceramic capacitors. Among these, the modulated Bi_0.5Na_0.5TiO₃ (BNT)-based ceramics can demonstrate favorable energy storage properties with antiferroelectric-like properties, simultaneously, attaching superior temperature stability resulted from the high Curie temperature. Inspired by the above properties, a strategy is proposed to modulate antiferroelectric-like properties via introducing Ca_0.7La_0.2TiO₃ (CLT) into Bi_0.395Na_0.325Sr_0.245TiO₃ (BNST) ((1−x)BNST-xCLT, x = 0.10, 0.15, 0.20, 0.25). Combining both orthorhombic phase and defect dipole designs successfully achieve antiferroelectric-like properties in BNST-CLT ceramics. The results illustrate that 0.8BNST-0.2CLT presents superior recoverable energy storage density ≈8.3 J cm⁻³ with the ideal η ≈ 80% at 660 kV cm⁻¹. Structural characterizations demonstrate that there is the intermediate modulated phase with the coexistence of the antiferroelectric and ferroelectric phases. In addition, in situ temperature measurements prove that BNST-CLT ceramics exhibit favorable temperature stability over a wide temperature range. The present work illustrates that BNT-based ceramics with antiferroelectric-like properties can effectively enhance the energy storage performance, which provides novel perspectives for the subsequent development of advanced pulsed capacitors.     

Synergistic Optimization of Energy Storage Density of PYN-Based Antiferroelectric Ceramics by Composition Design and Microstructure Engineering

PbYb_0.5Nb_0.5O₃ (PYN)-based ceramics, featured by their ultra-high phase-switching field and low sintering temperature (950 °C), are of great potential in exploiting dielectric ceramics with high energy storage density and low preparation cost. However, due to insufficient breakdown strength (BDS), their complete polarization-electric field (P-E) loops are difficult to be obtained. Here, to fully reveal their potential in energy storage, synergistic optimization strategy of composition design with Ba²⁺ substitution and microstructure engineering via hot-pressing (HP) are adopted in this work. With 2 mol% Ba²⁺ doping, a recoverable energy storage density (W_rec) of 10.10 J cm⁻³ and a discharge energy density (W_dis) of 8.51 J cm⁻³ can be obtained, supporting the superior current density (C_D) of 1391.97 A cm⁻² and the outstanding power density (P_D) of 417.59 MW cm⁻². In situ characterization methods are utilized here to reveal the unique movement of the B-site ions of PYN-based ceramics under electric field, which is the key factor of the ultra-high phase-switching field. It is also confirmed that microstructure engineering can refine the grain of ceramics and improve BDS. This work strongly demonstrates the potential of PYN-based ceramics in energy storage field and plays a guiding role in the follow-up research.     

Effects of sintering method on the structural,dielectric and energy storage properties of AgNbO3 lead-free antiferroelectric ceramics

In this work, we systematically investigated the effects of single-step and two-step sintering methods on the structural, dielectric and energy storage properties of pure AgNbO₃ lead-free antiferroelectric ceramics. Compared with the single-step sintered ceramic, the ceramic prepared by two-step sintering method has smaller grain size, dense and homogeneous microstructure. In addition, the results of dielectric temperature spectra reveal that the two-step sintering method hardly changes the phase transition temperature of AgNbO₃ ceramics but greatly decreases the dielectric loss value. Most importantly, the ceramic prepared by the two-step sintering method displays high breakdown electric field strength (22 kV/mm), larger recoverable energy storage density-W_rec (2.59 J/cm³) and higher energy storage efficiency-η (45%) as well as excellent temperature stability than those of the ceramic by single-step sintering method. Furthermore, it also exhibited high power density (P_D?=?25.7 MW/cm³) and extremely fast charge–discharge speed (25 ns). Our results provide a simple and novel way to design high-performance AgNbO₃-based energy storage lead-free ceramics.

Graphical abstract

     

Enhanced energy storage properties in lead-free NaNbO3–Sr0.7Bi0.2TiO3–BaSnO3 ternary ceramic

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(0.80NaNbO₃–0.20Sr_0.7Bi_0.2TiO₃)–0.10BaSnO₃ ceramic with high recoverable energy storage density (W_r?=?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 (ΔW_r?<?10% over 20–120 °C at 200 kV/cm) and fatigue resistance (ΔW_r?<?1% after 120,000 electrical cycles at 200 kV/cm) are observed, indicating that the 0.90(0.80NaNbO₃–0.20Sr_0.7Bi_0.2TiO₃)–0.10BaSnO₃ ceramics have promising application prospect for high-temperature energy storage devices in pulse power applications.

     

An Electrically Modulated Single-Color/Dual-Color Imaging Photodetector

An electrically modulated single-/dual-color imaging photodetector with fast response speed is developed based on a small molecule (CO_i8DFIC)/perovskite (CH₃NH₃PbBr₃) hybrid film. Owing to the type-I heterojunction, the device can facilely transform dual-color images to single-color images by applying a small bias voltage. The photodetector exhibits two distinct cut-off wavelengths at ≈544 nm (visible region) and ≈920 nm (near-infrared region), respectively, without any power supply. Its two peak responsivities are 0.16 A W⁻¹ at ≈525 nm and 0.041 A W⁻¹ at ≈860 nm with a fast response speed (≈10² ns). Under 0.6 V bias, the photodetector can operate in a single-color mode with a peak responsivity of 0.09 A W⁻¹ at ≈475 nm, showing a fast response speed (≈10² ns). A physical model based on band energy theory is developed to illustrate the origin of the tunable single-/dual-color photodetection. This work will stimulate new approaches for developing solution-processed multifunctional photodetectors for imaging photodetection in complex circumstances.     

Dense PLZT films grown on nickel substrates by PVP-modified sol–gel method

We have successfully grown ferroelectric Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) films on base metal foils by chemical solution deposition using sol–gel solutions containing polyvinylpyrrolidone. Under zero-bias field, we measured a dielectric constant of ≈820 and dielectric loss of ≈0.06 at room temperature, and a dielectric constant of ≈1250 and dielectric loss of ≈0.03 at 150 °C. In addition, leakage current density of ≈1.5 × 10^?8 A/cm², remanent polarization of ≈11.2 μC/cm², and coercive field of ≈40.6 kV/cm were measured at room temperature on a ≈3-μm-thick PLZT film grown on LaNiO₃-buffered nickel substrate. Finally, energy density ≈25 J/cm³ was measured from the P–E hysteresis loop at an applied field of 2 × 10⁶ V/cm.     

Stabilizing Antiferroelectric-Like Aluminum-Doped Hafnium Oxide for Energy Storage Capacitors

Herein, a systematic study of aluminum-doped hafnium oxide to utilize its antiferroelectric-like (AFE) properties for energy storage applications is done. The doping concentration of aluminum is optimized to obtain the AFE-like phase. In addition, the impact of the postmetallization annealing temperature on the energy storage properties of the materials is studied. Metal–insulator–metal capacitors are fabricated by varying the doping concentration of the Al in HfO₂ from 1.9 to 6.2 at% with a constant thickness of 10 nm by atomic layer deposition. The devices are rapid thermal annealed by varying the annealing temperature from 650 to 800 °C for 20 s. Polarization measurements indicate a clear phase transformation from ferroelectric (FE) to AFE to paraelectric phase with the increase of doping concentration in the polarization measurements. The planar antiferroelectric devices have an energy storage density of 30 J cm⁻³ with 76% efficiency after 10⁵ cycles. The storage density can be further increased by a factor of 16.5 using area-enhanced substrates to 500 J cm^{− 3} at 73% efficiency. The endurance characteristics are studied for both planar and 3D capacitors which are found to be stable up to 10⁸ cycles.     

Negatively Charged Nanosheets Significantly Enhance the Energy-Storage Capability of Polymer-Based Nanocomposites

Polymer-based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy-storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages. Here, a general strategy is proposed to significantly improve their breakdown strength and energy storage by adding negatively charged Ca₂Nb₃O₁₀ nanosheets. A dramatically enhanced breakdown strength (792 MV m⁻¹) and the highest energy density (36.2 J cm⁻³) among all flexible polymer-based dielectrics are observed in poly(vinylidene fluoride)-based nanocomposite capacitors. The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene-based nanocomposites. Phase-field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca₂Nb₃O₁₀ nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact-ionized electrons and blocks the breakdown path in nanocomposites. The results demonstrate a new horizon of high-energy-density flexible capacitors.     

Lead‐Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance

Antiferroelectric materials that display double ferroelectric hysteresis loops are receiving increasing attention for their superior energy storage density compared to their ferroelectric counterparts. Despite the good properties obtained in antiferroelectric La‐doped Pb(Zr,Ti)O₃‐based ceramics, lead‐free alternatives are highly desired due to the environmental concerns, and AgNbO₃ has been highlighted as a ferrielectric/antiferroelectric perovskite for energy storage applications. Enhanced energy storage performance, with recoverable energy density of 4.2 J cm^?3 and high thermal stability of the energy storage density (with minimal variation of ≤±5%) over 20–120 °C, can be achieved in Ta‐modified AgNbO₃ ceramics. It is revealed that the incorporation of Ta to the Nb site can enhance the antiferroelectricity because of the reduced polarizability of B‐site cations, which is confirmed by the polarization hysteresis, dielectric tunability, and selected‐area electron diffraction measurements. Additionally, Ta addition in AgNbO₃ leads to decreased grain size and increased bulk density, increasing the dielectric breakdown strength, up to 240 kV cm^?1 versus 175 kV cm^?1 for the pure counterpart, together with the enhanced antiferroelectricity, accounting for the high energy storage density.     

Multilayer Lead‐Free Ceramic Capacitors with Ultrahigh Energy Density and Efficiency

The utilization of antiferroelectric (AFE) materials is thought to be an effective approach to enhance the energy density of dielectric capacitors. However, the high energy dissipation and inferior reliability that are associated with the antiferroelectric–ferroelectric phase transition are the main issues that restrict the applications of antiferroelectric ceramics. Here, simultaneously achieving high energy density and efficiency in a dielectric ceramic is proposed by combining antiferroelectric and relaxor features. Based on this concept, a lead‐free dielectric (Na_0.5Bi_0.5)TiO₃‐x(Sr_0.7Bi_0.2)TiO₃ (NBT‐xSBT) system is investigated and the corresponding multilayer ceramic capacitors (MLCCs) are fabricated. A record‐high energy density of 9.5 J cm^?3, together with a high energy efficiency of 92%, is achieved in NBT‐0.45SBT multilayer ceramic capacitors, which consist of ten dielectric layers with the single‐layer thickness of 20 µm and the internal electrode area of 6.25 mm². Furthermore, the newly developed capacitor exhibits a wide temperature usage range of ‐60 to 120 °C, with an energy‐density variation of less than 10%, and satisfactory cycling reliability, with degradation of less than 8% over 10⁶ cycles. These characteristics demonstrate that the NBT‐0.45SBT multilayer ceramic is a promising candidate for high‐power energy storage applications.     

Multilayer PZT 95/5 Antiferroelectric Film Energy Storage Devices with Giant Power Density

A new type of energy storage devices utilizing multilayer Pb(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ films is studied experimentally and numerically. To release the stored energy, the multilayer ferroelectric structures are subjected to adiabatic compression perpendicular to the polarization direction. Obtained results indicate that electrical interference between layers (10–120 layers) during stress wave transit through the structures has an effect on the generated current waveforms, but no impact on the released electric charge. The multilayer films undergo a pressure‐induced phase transition to antiferroelectric phase at 1.7 GPa adiabatic compression and become completely depolarized, releasing surface screening charge with density equal to their remnant polarization. An energy density of 3 J cm^?3 is successfully achieved with giant power density on the order of 2 MW cm^?3, which is four orders of magnitude higher than that of any other type of energy storage device. The outputs of multilayer structures can be precisely controlled by the parameters of the ferroelectric layer and the number of layers. Multilayer film modules with a volume of 0.7 cm³ are capable of producing 2.4 kA current, not achievable in electrochemical capacitors or batteries, which will greatly enhance the miniaturization and integration requirements for emerging high‐power applications.     

Deeply Reconstructed Hierarchical Ni–Co Microwire for Flexible Ni–Zn Microbattery with Excellent Comprehensive Performance

The rise of flexible electronics calls for efficient microbatteries (MBs) with requirements in energy/power density, stability, and flexibility simultaneously. However, the ever-reported flexible MBs only display progress around certain aspects of energy loading, reaction rate, and electrochemical stability, and it remains challenging to develop a micro-power source with excellent comprehensive performance. Herein, a reconstructed hierarchical Ni–Co alloy microwire is designed to construct flexible Ni–Zn MB. Notably, the interwoven microwires network is directly formed during the synthesis process, and can be utilized as a potential microelectrode which well avoids the toxic additives and the tedious traditional powder process, thus greatly simplifying the manufacture of MB. Meanwhile, the hierarchical alloy microwire is composed of spiny nanostructures and highly active alloy sites, which contributes to deep reconstruction (≈100 nm). Benefiting from the dense self-assembled structure, the fabricated Ni–Zn MB obtained high volumetric/areal energy density (419.7 mWh cm⁻³, 1.3 mWh cm⁻²), and ultrahigh rate performance extending the power density to 109.4 W cm⁻³ (328.3 mW cm⁻²). More surprisingly, the MB assembled by this inherently flexible microwire network is extremely resistant to bending/twisting. Therefore, this novel concept of excellent comprehensive micro-power source will greatly hold great implications for next-generation flexible electronics.     

Enhanced Piezoelectric,Ferroelectric, and Electrostrictive Properties of Lead-Free (1-x)BCZT-(x)BCST Electroceramics with Energy Harvesting Capability

Next-generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)-free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials’ design with multi-phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead-free piezoelectric materials (1-x)Ba_0.95Ca_0.05Ti_0.95Zr_0.05O₃-(x)Ba_0.95Ca_0.05Ti_0.95Sn_0.05O₃, are reported, which are represented as (1-x)BCZT-(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1-x)BCZT-(x)BCST materials are synthesized by high-temperature solid-state ceramic reaction method by varying x in the full range (x = 0.00–1.00). In-depth exploration research is performed on the structural, dielectric, ferroelectric, and electro-mechanical properties of (1-x)BCZT-(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca²⁺, Zr⁴⁺, and Sn⁴⁺ are well dispersed within the BaTiO₃ lattice. For all (1-x)BCZT-(x)BCST ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 + P4mm) phases at room temperature. The steady transition of Amm2 crystal symmetry to P4mm crystal symmetry with increasing x content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral-orthorhombic (T_R-O), orthorhombic- tetragonal (T_O-T), and tetragonal-cubic (T_C), gradually shift toward lower temperature with increasing x content. For (1-x)BCZT-(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constant ε_r ≈ 1900–3300 (near room temperature), ε_r ≈ 8800–12 900 (near Curie temperature), dielectric loss, tan δ ≈ 0.01–0.02, remanent polarization P_r ≈ 9.4–14 µC cm⁻², coercive electric field E_c ≈ 2.5–3.6 kV cm⁻¹. Further, high electric field-induced strain S ≈ 0.12–0.175%, piezoelectric charge coefficient d₃₃ ≈ 296–360 pC N⁻¹, converse piezoelectric coefficient ${(d_{33}^{\ast })}_{\mathrm{ave}}$≈ 240–340 pm V⁻¹, planar electromechanical coupling coefficient k_p ≈ 0.34–0.45, and electrostrictive coefficient (Q₃₃)_avg ≈ 0.026–0.038 m⁴ C⁻² are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT-(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead-free piezoelectric (1-x)BCZT-(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1-x)BCZT-(x)BCST ceramics as a potentially strong contender within the family of Pb-free piezoelectric materials for future electronics and energy harvesting device technologies.     

Tailoring Poly(Styrene-co-maleic anhydride) Networks for All-Polymer Dielectrics Exhibiting Ultrahigh Energy Density and Charge–Discharge Efficiency at Elevated Temperatures

Polymer film capacitors have been widely used in electronics and electrical power systems due to their advantages of high power densities, fast charge–discharge speed, and great stability. However, the exponential increase of electrical conduction with temperature and applied electric field substantially degrades the capacitive performance of dielectric polymers at elevated temperatures. Here, the first example of controlling the energy level of charge traps in all-organic crosslinked polymers by tailoring molecular structures that significantly inhibit high-field high-temperature conduction loss, which largely differs from current approaches based on the introduction of inorganic fillers, is reported. The polymer network with optimized crosslinking structures exhibits an ultrahigh discharged energy density of 7.02 J cm⁻³ with charge/discharge efficiencies of >90% at 150 °C, far outperforming current dielectric polymers and composites. The charge-trapping effects in different crosslinked structures, as the origins of the marked improvements in the high-temperature capacitive performance, are comprehensively investigated experimentally and confirmed computationally. Moreover, excellent cyclability and self-healing features are demonstrated in the polymer film capacitors. This work offers a promising pathway of molecular structure design to scalable high-energy-density polymer dielectrics capable of operating under harsh environments.