High-Performance Ferroelectric Electromagnetic Attenuation Materials with Multiple Polar Units Based on Nanodomain Engineering

Achieving Ultrahigh Electrocaloric Response in (Bi0.5Na0.5)TiO3-Based Ceramics through B-Site Defect Engineering

Lead-free electrocaloric (EC) ferroelectrics are considered ideal for the next generation of environmentally friendly solid-state refrigeration materials. However, their inferior performance compared to lead-based materials significantly restricts their potential application. According to phase-field simulations, it is predicted that the pinning effect of a moderate number of defects can effectively enhance the reversible polarization response associated with the entropy change. Herein, sodium-bismuth titanate (BNT) ceramics with high spontaneous polarization are selected to construct B-site defects by introducing Li+ and Nb5+. Under an electric field of 6 kV mm-1, ultrahigh EC temperature changes of ΔTpos = 1.77 and ΔTneg = 1.49 K are achieved at 65 °C by direct measurement (ΔTneg > 1 K over 55-120 °C). Furthermore, ΔTneg remains above 0.70 K in the temperature range from 25 to 130 °C, exhibiting immense potential for practical applications. This study offers a promising direction for optimizing the EC response in defect systems.

Charge Dynamics Engineering Sparks Hetero-Interfacial Polarization for an Ultra-Efficient Microwave Absorber with Mechanical Robustness

Microwave absorbers with high efficiency and mechanical robustness are urgently desired to cope with more complex and harsh application scenarios. However, manipulating the trade-off between microwave absorption performance and mechanical properties is seldom realized in microwave absorbers. Here, a chemistry-tailored charge dynamic engineering strategy is proposed for sparking hetero-interfacial polarization and thus coordinating microwave attenuation ability with the interfacial bonding, endowing polymer-based composites with microwave absorption efficiency and mechanical toughness. The absorber designed by this new conceptual approach exhibits remarkable Ku-band microwave absorption efficiency (-55.3 dB at a thickness of 1.5 mm) and satisfactory effective absorption bandwidth (5.0 GHz) as well as desirable interfacial shear strength (97.5 MPa). The calculated differential charge density depicts the uneven distribution of space charge and the intense hetero-interfacial polarization, clarifying the structure-performance relationship from a theoretical perspective. This work breaks through traditional single performance-oriented design methods and ushers a new direction for next-generation microwave absorbers.

Self-Recovery of a Buckling BaTiO3 Ferroelectric Membrane

The characteristic of self-recovery holds significant implications for upholding performance stability within flexible electronic devices following the release of mechanical deformation. Herein, the dynamics of self-recovery in a buckling inorganic membrane is studied via in situ scanning probe microscopy technology. The experimental results demonstrate that the ultimate deformation ratio of the buckling BaTiO3 ferroelectric membrane is up to 88%, which is much higher than that of the buckling SrTiO3 dielectric membrane (49%). Combined with piezoresponse force microscopy and phase-field simulations, we find that ferroelectric domain transformation accompanies the whole process of buckling and self-recovery of the ferroelectric membrane, i.e., the presence of the nano-c domain not only releases part of the elastic energy of the membrane but also reduces the interface mismatch of the a/c domain, which encourages the buckling ferroelectric membrane to have excellent self-recovery properties. It is conceivable that the evolution of ferroelectric domains will play a greater role in the regulation of the mechanical properties of ferroelectric membranes and flexible devices.

Enhanced Energy Storage Properties in Lead-Free (Na0.5Bi0.5)0.7Sr0.3TiO3-Based Relaxor Ferroelectric Ceramics through a Cooperative Optimization Strategy

Although relaxor ferroelectrics have been widely investigated owing to their various advantages, there are still impediments to boosting their energy-storage density (W_rec) and energy-storage efficiency (η). In this paper, we propose a cooperative optimization strategy for achieving comprehensive outstanding energy-storage performance in (Na_0.5Bi_0.5)_0.7Sr_0.3TiO₃ (NBST)-based ceramics by triggering a nonergodic-to-ergodic transformation and optimizing the forming process. The first step of substituting NaNbO₃ (NN) for NBST generated an ergodic state and induced polar nanoregions under the guidance of a phase-field simulation. The second step was to apply a viscous polymer process (VPP) to the 0.85NBST-0.15NN ceramics, which reduced porosity and increased compactness, resulting in a significant polarization difference and high breakdown strength. Consequently, 0.85NBST-0.15NN-VPP ceramics optimized by this cooperative two-step strategy possessed improved energy-storage characteristics (W_rec = 7.6 J/cm³, η = 90%) under 410 kV/cm as well as reliable temperature adaptability within a range of 20-120 °C, outperforming most reported (Na_0.5Bi_0.5) TiO₃-based ceramics. The improved energy-storage performance validates the developed ceramics' practical applicability as well as the advantages of implementing a cooperative optimization technique to fabricate similar high-performance dielectric ceramics.

Significantly Enhanced Energy Storage Performance in High Hardness BKT-Based Ceramic via Defect Engineering and Relaxor Tuning

Hybrid electric cars and pulsed power technologies have increased the demand for capacitors with high energy density, wide temperature stability, high operating voltage, and good mechanical qualities. In this work, (1 - x) (0.6Bi_0.5K_0.5TiO₃-0.4BiFeO₃)-x(Na_0.4Sm_0.2NbO₃) ((1 - x) (BKTBF)-xNSN) relaxor ceramics were prepared by constructing morphotropic phase boundary (MPB) combined with oxygen vacancy defect engineering. It is worth noting that the 0.6BKT-0.4BFO ceramics at MPB have a high P_max ∼ 60 μC/cm². The ultra-hard (H_V = 10.7 GPa) BKTBFO-0.16NSN relaxor ferroelectric ceramic achieves a high W_rec of 6.52 J/cm³, a working temperature of 20-120 °C, and a working frequency of 1-1000 Hz. Additionally, the BKTBFO-0.16NSN ceramic demonstrates comprehensive pulse charge-discharge performance (I_max = 17.2 A, C_D = 546.7 A/cm², P_D = 54.7 MW/cm³, and t_0.9 = 59 ns) and excellent stability (25-125 °C and 10⁴ charge-discharge cycles). This study offers a novel approach for the practical implementation of high-performance pulse capacitors, which will undoubtedly stimulate further research and development of high-P_max energy storage dielectrics (such as BNT, BKT, and BFO).

High Energy Storage Performance in La-Doped AgNbO3 Ceramics via Tape Casting

AgNbO₃-based Pb-free antiferroelectric (AFE) ceramics have attracted increasing interest owing to their excellent potential in energy storage applications. Herein, a high recoverable energy storage density (W_rec) of 7.62 J/cm³ is realized in La-doped AgNbO₃ ceramics prepared via tape casting. The high W_rec is attributed to high breakdown strength E_b of 380 kV/cm induced by dense microstructure as well as fine grain size and enhanced AFE stability stemming from M₂ phase and reduced tolerance factor t. The high W_rec exceeding 6 J/cm³ was maintained in a wide temperature range of 20-150 °C and exhibited frequency stability with less than 8% variation in a range of 1-200 Hz. The discharge energy density W_d exhibited temperature stability at 30-110 °C with less than 9% variation. Our research provides a good method for producing AgNbO₃-based ceramics having high energy storage performances.

Enhanced Energy-Storage Performances in Sodium Bismuth Titanate-Based Relaxation Ferroelectric Ceramics with Optimized Polarization by Tuning Sintering Temperature

Energy-storage capacitors based on relaxation ferroelectric ceramics have attracted a lot of interest in pulse power devices. How to improve the energy density by designing the structure of ceramics through simple approaches is still a challenge. Herein, enhanced energy-storage performances are achieved in relaxation ferroelectric 0.9 (0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃)-0.1NaNbO₃ (NBT-BT-NN) ceramics by tuning sintering temperature. The original observation based on Kelvin probe force microscopy (KPFM) presented that the sintering temperature has a key effect on the electrical homogeneousness of the ceramics. It is found that a high electrical homogeneousness can induce quick and active domain switching due to the weakening of the constraint from built-in fields, resulting in a big polarization difference. This work provides a feasible strategy to design high-performance energy-storage ceramic capacitors.

Ultrahigh Energy-Storage Performances in Lead-free Na0.5Bi0.5TiO3-Based Relaxor Antiferroelectric Ceramics through a Synergistic Design Strategy

Dielectric ceramics with outstanding energy-storage performances are nowadays in great demand for pulsed power electronic systems. Here, we propose a synergistic design strategy to significantly enhance the energy-storage properties of (1 - x)(0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃)-xCaTi_0.75Ta_0.2O₃ solid solution ceramics through introducing polar nanoregions, shifting rhombohedral to tetragonal phase transition below room temperature (stable antiferroelectric characteristic), as well as increasing the band gap in the system. Ultrahigh energy-storage properties with a record value of recoverable energy-storage density W_rec ∼ 9.55 J/cm³ and a high efficiency η ∼ 88% are achieved in Na_0.5Bi_0.5TiO₃-based bulk ceramics with x = 0.24. Moreover, high W_rec (>3.4 J/cm³) and η (>90%) with a variation of less than 6% can be observed in a wide frequency and temperature frequency range of 5-200 Hz and 25-140 °C. Our research result not only indicates the great possibility of Na_0.5Bi_0.5TiO₃-based lead-free compositions to replace lead-based energy-storage ceramics but also gives an effective strategy to design ultrahigh energy-storage performances for eco-friendly ceramics.

Constructing Relaxor/Ferroelectric Pseudocomposite To Reveal the Domain Role in Electrostrain of Bismuth Ferrite-Barium Titanate Based Ceramics

Bismuth ferrite-barium titanate (BF-BT) based ceramics have attracted extensive attention due to its excellent energy conversion. Recently it has been found that BF-BT based ceramics with large electrostrain are usually accompanied by a special domain configuration in which weak and strong piezoresponse domain grains coexist. In this work, we purposefully constructed the special domain configuration in the pseudocomposite ceramics of (1 - x)0.55BF-0.4BT-0.05BZN/x(0.7BF-0.3BT) (relaxor-like phase/ferroelectric phase, RE/FE) by a "two-step" method. Macroproperty characterization suggests that the critical component pseudocomposite ceramic (x = 50%) with the special domain structure can exhibit a maximum electrostrain value (S ∼ 0.28%) at 6 kV/mm, almost 3-fold to that (S ∼ 0.1%) of the two end members and 63% higher than that (S ∼ 0.17%) of the same component ceramic prepared by the "one-step" method. Further mesoscopic structure results show that the "two-phase" composite can induce the formation of grain dependent domain at nanoscale, and just this special domain conformation is conducive to a significant improvement in electrostrain. Therefore, the large strain in BF-BT-based ceramics is mainly caused by the special microstructure rather than component.