Balancing Polarization and Breakdown for High Capacitive Energy Storage by Microstructure Design.

The compromise of contradictive parameters, polarization, and breakdown strength, is necessary to achieve a high energy storage performance. The two can be tuned, regardless of material types, by controlling microstructures: amorphous states possess higher breakdown strength, while crystalline states have larger polarization. However, how to achieve a balance of amorphous and crystalline phases requires systematic and quantitative investigations. Herein, the trade-off between polarization and breakdown field is comprehensively evaluated with the evolution of microstructure, i.e., grain size and crystallinity, by phase-field simulations. The results indicate small grain size (≈10-35 nm) with moderate crystallinity (≈60-80%) is more beneficial to maintain relatively high polarization and breakdown field simultaneously, consequently contributing to a high overall energy storage performance. Experimentally, therefore an ultrahigh energy density of 131 J cm-3 is achieved with a high efficiency of 81.6% in the microcrystal-amorphous dual-phase Bi3NdTi4O12 films. This work provides a guidance to substantially enhance dielectric energy storage by a simple and effective microstructure design.

Enhancing Kinetics in Sodium Super Ion Conductor Na3MnTi(PO4)3 through Microbe-Assisted and Structural Optimization.

Sodium (Na) super ion conductor (NASICON) structure Na3MnTi(PO4)3 (NMTP) is considered a promising cathode for sodium-ion batteries due to its reversible three-electron reaction. However, the inferior electronic conductivity and sluggish reaction kinetics limit its practical applications. Herein, we successfully constructed a three-dimensional cross-linked porous architecture NMTP material (AsN@NMTP/C) by a natural microbe of Aspergillus niger (AsN), and the structure of different NMTP cathodes was optimized by adjusting different transition metal Mn/Ti ratios. Both approaches effectively altered the three-dimensional NMTP structure, not only improving electronic conductivity and controlling Na+ diffusion pathways but also enhancing the electrochemical kinetics of the material. The resultant AsN@NMTP/C-650, sintered at 650 °C, exhibits better electrochemical performance with higher reversible three-electron reactions corresponding to the voltage platforms of Ti4+/3+, Mn3+/2+, and Mn4+/3+ around 2.1, 3.6, and 4.1 V (vs Na+/Na), respectively. The capacity retention rate is up to 89.3% after 1000 cycles at a 2C rate. Moreover, a series of results confirms that the Na3.4Mn1.2Ti0.8(PO4)3 cathode has the most excellent electrochemical performance when the Mn/Ti ratio is 1.2/0.8, with a high capacity of 96.59 mAh g-1 and 97.1% capacity retention after 500 cycles.

Ultrahigh energy storage in high-entropy ceramic capacitors with polymorphic relaxor phase.

Ultrahigh-power-density multilayer ceramic capacitors (MLCCs) are critical components in electrical and electronic systems. However, the realization of a high energy density combined with a high efficiency is a major challenge for practical applications. We propose a high-entropy design in barium titanate (BaTiO3)-based lead-free MLCCs with polymorphic relaxor phase. This strategy effectively minimizes hysteresis loss by lowering the domain-switching barriers and enhances the breakdown strength by the high atomic disorder with lattice distortion and grain refining. Benefiting from the synergistic effects, we achieved a high energy density of 20.8 joules per cubic centimeter with an ultrahigh efficiency of 97.5% in the MLCCs. This approach should be universally applicable to designing high-performance dielectrics for energy storage and other related functionalities.

Boosting Thermoelectric Performance via Weakening Carrier-Phonon Coupling in BiCuSeO-Graphene Composites.

BiCuSeO is a promising oxygen-containing thermoelectric material due to its intrinsically low lattice thermal conductivity and excellent service stability. However, the low electrical conductivity limits its thermoelectric performance. Aliovalent element doping can significantly improve their carrier concentration, but it may also impact carrier mobility and thermal transport properties. Considering the influence of graphene on carrier-phonon decoupling, Bi0.88 Pb0.06 Ca0.06 CuSeO (BPCCSO)-graphene composites are designed. For further practical application, a rapid preparation method is employed, taking less than 1 h, which combines self-propagating high-temperature synthesis with spark plasma sintering. The incorporation of graphene simultaneously optimizes the electrical properties and thermal conductivity, yielding a high ratio of weighted mobility to lattice thermal conductivity (144 at 300 K and 95 at 923 K). Ultimately, BPCCSO-graphene composites achieve exceptional thermoelectric performance with a ZT value of 1.6 at 923 K, bringing a ≈40% improvement over BPCCSO without graphene. This work further promotes the practical application of BiCuSeO-based materials and this facile and effective strategy can also be extended to other thermoelectric systems.

Thermoelectrocatalysis: an emerging strategy for converting waste heat into chemical energy.

This perspective defines and explores an innovative waste heat harvesting strategy, thermoelectrocatalysis (TECatal), emphasizing materials design and potential applications in clean energy, environmental, and biomedical technologies.

Electric-Field Control of Perpendicularly Magnetized Ferrimagnetic Order and Giant Magnetoresistance in Multiferroic Heterostructures.

Electrical control of magnetism is highly desirable for energy-efficient spintronic applications. Realizing electric-field-driven perpendicular magnetization switching has been a long-standing goal, which, however, remains a major challenge. Here, electric-field control of perpendicularly magnetized ferrimagnetic order via strain-mediated magnetoelectric coupling is reported. We show that the gate voltages isothermally toggle the dominant magnetic sublattice of the compensated ferrimagnet FeTb at room temperature, showing high reversibility and good endurance under ambient conditions. By implementing this strategy in FeTb/Pt/Co spin valves with giant magnetoresistance (GMR), we demonstrate that the distinct high and low resistance states can be selectively controlled by the gate voltages with assisting magnetic fields. Our results provide a promising route to use ferrimagnets for developing electric-field-controlled, low-power memory and logic devices.

Field-free spin-orbit switching of perpendicular magnetization enabled by dislocation-induced in-plane symmetry breaking.

Current induced spin-orbit torque (SOT) holds great promise for next generation magnetic-memory technology. Field-free SOT switching of perpendicular magnetization requires the breaking of in-plane symmetry, which can be artificially introduced by external magnetic field, exchange coupling or device asymmetry. Recently it has been shown that the exploitation of inherent crystal symmetry offers a simple and potentially efficient route towards field-free switching. However, applying this approach to the benchmark SOT materials such as ferromagnets and heavy metals is challenging. Here, we present a strategy to break the in-plane symmetry of Pt/Co heterostructures by designing the orientation of Burgers vectors of dislocations. We show that the lattice of Pt/Co is tilted by about 1.2° when the Burgers vector has an out-of-plane component. Consequently, a tilted magnetic easy axis is induced and can be tuned from nearly in-plane to out-of-plane, enabling the field-free SOT switching of perpendicular magnetization components at room temperature with a relatively low current density (~1011 A/m2) and excellent stability (> 104 cycles). This strategy is expected to be applicable to engineer a wide range of symmetry-related functionalities for future electronic and magnetic devices.

End-to-end affine registration framework for histopathological images with weak annotations.

BACKGROUND AND OBJECTIVE: Histopathological image registration is an essential component in digital pathology and biomedical image analysis. Deep-learning-based algorithms have been proposed to achieve fast and accurate affine registration. Some previous studies assume that the pairs are free from sizeable initial position misalignment and large rotation angles before performing the affine transformation. However, large-rotation angles are often introduced into image pairs during the production process in real-world pathology images. Reliable initial alignment is important for registration performance. The existing deep-learning-based approaches often use a two-step affine registration pipeline because convolutional neural networks (CNNs) cannot correct large-angle rotations. METHODS: In this manuscript, a general framework ARoNet is developed to achieve end-to-end affine registration for histopathological images. We use CNNs to extract global features of images and fuse them to construct correspondent information for affine transformation. In ARoNet, a rotation recognition network is implemented to eliminate great rotation misalignment. In addition, a self-supervised learning task is proposed to assist the learning of image representations in an unsupervised manner. RESULTS: We applied our model to four datasets, and the results indicate that ARoNet surpasses existing affine registration algorithms in alignment accuracy when large angular misalignments (e.g., 180 rotation) are present, providing accurate affine initialization for subsequent non-rigid alignments. Besides, ARoNet shows advantages in execution time (0.05 per pair), registration accuracy, and robustness. CONCLUSION: We believe that the proposed general framework promises to simplify and speed up the registration process and has the potential for clinical applications.

Polar Solomon rings in ferroelectric nanocrystals.

Solomon rings, upholding the symbol of wisdom with profound historical roots, were widely used as decorations in ancient architecture and clothing. However, it was only recently discovered that such topological structures can be formed by self-organization in biological/chemical molecules, liquid crystals, etc. Here, we report the observation of polar Solomon rings in a ferroelectric nanocrystal, which consist of two intertwined vortices and are mathematically equivalent to a [Formula: see text] link in topology. By combining piezoresponse force microscopy observations and phase-field simulations, we demonstrate the reversible switching between polar Solomon rings and vertex textures by an electric field. The two types of topological polar textures exhibit distinct absorption of terahertz infrared waves, which can be exploited in infrared displays with a nanoscale resolution. Our study establishes, both experimentally and computationally, the existence and electrical manipulation of polar Solomon rings, a new form of topological polar structures that may provide a simple way for fast, robust, and high-resolution optoelectronic devices.

Compositing effects for high thermoelectric performance of Cu2Se-based materials.

Thermoelectric materials can realize direct conversion between heat and electricity, showing excellent potential for waste heat recovery. Cu2Se is a typical superionic conductor thermoelectric material having extraordinary ZT values, but its superionic feature causes poor service stability and low mobility. Here, we reported a fast preparation method of self-propagating high-temperature synthesis to realize in situ compositing of BiCuSeO and Cu2Se to optimize the service stability. Additionally, using the interface design by introducing graphene in these composites, the carrier mobility could be obviously enhanced, and the strong phonon scatterings could lead to lower lattice thermal conductivity. Ultimately, the Cu2Se-BiCuSeO-graphene composites presented excellent thermoelectric properties with a ZTmax value of ~2.82 at 1000 K and a ZTave value of ~1.73 from 473 K to 1000 K. This work provides a facile and effective strategy to largely improve the performance of Cu2Se-based thermoelectric materials, which could be further adopted in other thermoelectric systems.

Robust, Flexible Thermoelectric Film for Energy Harvesting by a Simple and Eco-Friendly Method.

As for the self-supporting composite films, it is significant to develop a structural design that allows for excellent flexibility while reducing the negative effect on thermoelectric (TE) properties. Herein, a robust, flexible TE film was fabricated by in situ chemical transformation and vacuum-assisted filtration without any organic solvents involved. The performance of the films was further optimized by adjusting the Ag/Te ratio and post-treatment methods. Owing to the semi-interpenetrating nanonetwork structure formed by AgxTe nanowires and bacterial cellulose, the obtained TE film displayed a high tensile strength of ∼78.4 MPa and a high power factor of 48.9 µW m-1 K-2 at room temperature. A slight electrical conductivity decrement of the TE film in flexible test (∼2% after 1000 bending cycles) indicates an excellent flexibility. Finally, a TE bracelet was assembled to harvest body heat energy, and a steady current of ∼2.7 µA was generated when worn on the wrist indoors. This work provides a reference for the structural design and practical application of flexible TE films.

Continuously released Zn2+ in 3D-printed PLGA/ß-TCP/Zn scaffolds for bone defect repair by improving osteoinductive and anti-inflammatory properties.

Long-term nonunion of bone defects has always been a major problem in orthopedic treatment. Artificial bone graft materials such as Poly (lactic-co-glycolic acid)/ß-tricalcium phosphate (PLGA/ß-TCP) scaffolds are expected to solve this problem due to their suitable degradation rate and good osteoconductivity. However, insufficient mechanical properties, lack of osteoinductivity and infections after implanted limit its large-scale clinical application. Hence, we proposed a novel bone repair bioscaffold by adding zinc submicron particles to PLGA/ß-TCP using low temperature rapid prototyping 3D printing technology. We first screened the scaffolds with 1 wt% Zn that had good biocompatibility and could stably release a safe dose of zinc ions within 16 weeks to ensure long-term non-toxicity. As designed, the scaffold had a multi-level porous structure of biomimetic cancellous bone, and the Young's modulus (63.41 ± 1.89 MPa) and compressive strength (2.887 ± 0.025 MPa) of the scaffold were close to those of cancellous bone. In addition, after a series of in vitro and in vivo experiments, the scaffolds proved to have no adverse effects on the viability of BMSCs and promoted their adhesion and osteogenic differentiation, as well as exhibiting higher osteogenic and anti-inflammatory properties than PLGA/ß-TCP scaffold without zinc particles. We also found that this osteogenic and anti-inflammatory effect might be related to Wnt/ß-catenin, P38 MAPK and NFkB pathways. This study lay a foundation for the follow-up study of bone regeneration mechanism of Zn-containing biomaterials. We envision that this scaffold may become a new strategy for clinical treatment of bone defects.

Fatigue behavior of zirconia with microgrooved surfaces produced using femtosecond laser.

Femtosecond laser is a promising surface treatment tool for zirconia implant. In this study, the fatigue behavior of zirconia specimens with microgrooved surfaces formed by femtosecond laser is reported. One hundred sixty CAD/CAM zirconia bars (20 mm × 4 mm × 1.4 mm) were evenly divided into four groups with different surface: as sintered; sandblasted with 110 µm Al2O3; femtosecond laser produced microgrooves having 50 µm width, 30 µm depth, and 100 µm pitch; microgrooves having 30 µm width, 20 µm depth, and 60 µm pitch. The femtosecond laser formed micro/nanostructured microgrooves with precise size on zirconia surfaces. XRD analysis indicated that microgrooved surface showed no obvious tetragonal-to-monoclinic phase transformation. The fatigue strength of sandblasted specimens (728 MPa) was significantly higher than that of as sintered specimens (570 MPa). However, the fatigue strength of specimens with microgrooved surface decreased to about 360-380 MPa. The results suggest femtosecond laser is an effective technique to regulate the surface microtopography of zirconia, while further investigations are needed to improve its fatigue behavior.

Significant Unconventional Anomalous Hall Effect in Heavy Metal/Antiferromagnetic Insulator Heterostructures.

The anomalous Hall effect (AHE) is a quantum coherent transport phenomenon that conventionally vanishes at elevated temperatures because of thermal dephasing. Therefore, it is puzzling that the AHE can survive in heavy metal (HM)/antiferromagnetic (AFM) insulator (AFMI) heterostructures at high temperatures yet disappears at low temperatures. In this paper, an unconventional high-temperature AHE in HM/AFMI is observed only around the Néel temperature of AFM, with large anomalous Hall resistivity up to 40 nΩ cm is reported. This mechanism is attributed to the emergence of a noncollinear AFM spin texture with a non-zero net topological charge. Atomistic spin dynamics simulation shows that such a unique spin texture can be stabilized by the subtle interplay among the collinear AFM exchange coupling, interfacial Dyzaloshinski-Moriya interaction, thermal fluctuation, and bias magnetic field.

A self-assembly growth strategy for a highly ordered ferroelectric nanoisland array.

Ferroelectric nanoislands have attracted intensive research interest due to their size effect induced exotic physical properties and potential applications in non-volatile ferroelectric memories. However, the self-assembly growth of highly ordered ferroelectric nanoisland arrays is still a challenge. Here, by patterning a LaAlO3 substrate with etched nanocavities to provide preferential nucleation sites, highly ordered self-assembled BiFeO3 nanoisland arrays with robust ferroelectric topological quad-domain configurations were achieved. From the thermodynamic and kinetic perspectives, three factors are critical for achieving highly ordered self-assembled nanoisland arrays, that is, preferential nucleation sites, an appropriate relationship between the surface energy and the interface energy, and the growth rate difference of films. This approach can also be employed for the self-assembly growth of nanoisland arrays in other ferroelectric materials, which facilitates the design of ferroelectric nanostructure-based nanodevices.

Excellent Energy Storage Properties Achieved in Sodium Niobate-Based Relaxor Ceramics through Doping Tantalum.

Lead-free relaxor ferroelectric ceramics are potential for energy storage applications due to their comprehensive energy storage properties. However, the energy efficiency of many relaxor ceramics is not high enough, leading to high Joule heat during the charge-discharge cycles, thus lowering their energy storage performance. In this work, tantalum (Ta) dopants were introduced into sodium niobate-based relaxor ceramics to improve the resistivity and energy efficiency. The leakage current was reduced by Ta doping, especially at the high electric field. The enhanced resistivity is attributed to the increased bandgap induced by Ta doping. The impedance spectroscopy shows that both the grain and grain boundary resistivities are improved in the high temperature region. As a result, the optimal recoverable energy density and energy efficiency are 6.5 J/cm3 and 94% at 450 kV/cm, respectively. In addition, the energy storage properties exhibit satisfactory temperature stability and cycling reliability. All these merits demonstrate that the Ta modified sodium niobate-based relaxor ceramic a potential candidate for high-power energy storage applications.

Ferroelectric domain-wall logic units.

The electronic conductivities of ferroelectric domain walls have been extensively explored over the past decade for potential nanoelectronic applications. However, the realization of logic devices based on ferroelectric domain walls requires reliable and flexible control of the domain-wall configuration and conduction path. Here, we demonstrate electric-field-controlled stable and repeatable on-and-off switching of conductive domain walls within topologically confined vertex domains naturally formed in self-assembled ferroelectric nano-islands. Using a combination of piezoresponse force microscopy, conductive atomic force microscopy, and phase-field simulations, we show that on-off switching is accomplished through reversible transformations between charged and neutral domain walls via electric-field-controlled domain-wall reconfiguration. By analogy to logic processing, we propose programmable logic gates (such as NOT, OR, AND and their derivatives) and logic circuits (such as fan-out) based on reconfigurable conductive domain walls. Our work might provide a potentially viable platform for programmable all-electric logic based on a ferroelectric domain-wall network with low energy consumption.

High-entropy enhanced capacitive energy storage.

Electrostatic dielectric capacitors are essential components in advanced electronic and electrical power systems due to their ultrafast charging/discharging speed and high power density. A major challenge, however, is how to improve their energy densities to effectuate the next-generation applications that demand miniaturization and integration. Here, we report a high-entropy stabilized Bi2Ti2O7-based dielectric film that exhibits an energy density as high as 182 J cm-3 with an efficiency of 78% at an electric field of 6.35 MV cm-1. Our results reveal that regulating the atomic configurational entropy introduces favourable and stable microstructural features, including lattice distorted nano-crystalline grains and a disordered amorphous-like phase, which enhances the breakdown strength and reduces the polarization switching hysteresis, thus synergistically contributing to the energy storage performance. This high-entropy approach is expected to be widely applicable for the development of high-performance dielectrics.

Mechanically Induced Highly Efficient Hydrogen Evolution from Water over Piezoelectric SnSe nanosheets.

Piezoelectric nanomaterials open new avenues in driving green catalysis processes (e.g., H2 evolution from water) through harvesting mechanical energy, but their catalytic efficiency is still limited. The predicted enormous piezoelectricity for 2D SnSe, together with its high charge mobility and excellent flexibility, renders it an ideal candidate for stimulating piezocatalysis redox reactions. In this work, few-layer piezoelectric SnSe nanosheets (NSs) are utilized for mechanically induced H2 evolution from water. The finite elemental method simulation demonstrates an unprecedent maximal piezoelectric potential of 44.1 V for a single SnSe NS under a pressure of 100 MPa. A record-breaking piezocurrent density of 0.3 mA cm-2 is obtained for SnSe NSs-based electrode under ultrasonic excitation (100 W, 45 kHz), which is about three orders of magnitude greater than that of reported piezocatalysts. Moreover, an exceptional H2 production rate of 948.4 µmol g-1 h-1 is achieved over the SnSe NSs without any cocatalyst, far exceeding most of the reported piezocatalysts and competitive with the current photocatalysis technology. The findings not only enrich the potential piezocatalysis materials, but also provide useful guidance toward high-efficiency mechanically driven chemical reactions such as H2 evolution from water.