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Electrocatalysts play a key role in accelerating the sluggish electrochemical CO2 reduction (ECR) involving multi‐electron and proton transfer. We now develop a proton capture strategy by accelerating the water dissociation reaction catalyzed by transition‐metal nanoparticles (NPs) adjacent to atomically dispersed and nitrogen‐coordinated single nickel (Ni−Nx) active sites to accelerate proton transfer to the latter for boosting the intermediate protonation step, and thus the whole ECR process. Aberration‐corrected scanning transmission electron microscopy, X‐ray absorption spectroscopy, and calculations reveal that the Ni NPs accelerate the adsorbed H (Had) generation and transfer to the adjacent Ni−Nx sites for boosting the intermediate protonation and the overall ECR processes. This proton capture strategy is universal to design and prepare for various high‐performance catalysts for diverse electrochemical reactions even beyond ECR. [ABSTRACT FROM AUTHOR]

Electrocatalysts play a key role in accelerating the sluggish electrochemical CO2 reduction (ECR) involving multi‐electron and proton transfer. We now develop a proton capture strategy by accelerating the water dissociation reaction catalyzed by transition‐metal nanoparticles (NPs) adjacent to atomically dispersed and nitrogen‐coordinated single nickel (Ni−Nx) active sites to accelerate proton transfer to the latter for boosting the intermediate protonation step, and thus the whole ECR process. Aberration‐corrected scanning transmission electron microscopy, X‐ray absorption spectroscopy, and calculations reveal that the Ni NPs accelerate the adsorbed H (Had) generation and transfer to the adjacent Ni−Nx sites for boosting the intermediate protonation and the overall ECR processes. This proton capture strategy is universal to design and prepare for various high‐performance catalysts for diverse electrochemical reactions even beyond ECR. [ABSTRACT FROM AUTHOR]

Accurate low-order structure factors (Fg) measured by quantitative convergent beam electron diffraction (QCBED) were used for validation of different density functional theory (DFT) approximations. Twenty-three low-order Fg were measured for the transition metals Cr, Fe, Co, Ni, and Cu, and the transition metal based intermetallic phases γ-TiAl, β-NiAl, and γ1-FePd using a multi-beam off-zone axis QCBED method and then compared with Fg calculated by ab initio DFT using the local density approximation (LDA) and LDA + U, and different generalized gradient approximations (GGA) functionals. Different functionals perform very differently for different materials and crystal structures regarding prediction of low-order Fg. All the GGA functionals tested in the paper except for EV93 achieve good overall agreement with the experimentally determined low-order Fg for BCC Cr and Fe, while EV93 performs the best for FCC Ni and Cu. The LDA and GGA functional fail to predict accurately the low-order Fg for β-NiAl and γ1-FePd. The LDA + U approach, through tuning of U, can achieve excellent matches with the experimentally measured Fg for all the metallic systems investigated in this paper. The use of experimentally accessible low order Fg as an additional set of metrics in approaches of validation of DFT calculations is discussed and has potential to assist in and to stimulate development of improved functionals. [ABSTRACT FROM AUTHOR]

Here we report the response of a high angle annular dark field scintillator-based detector to single electrons. We demonstrate that care must be taken when determining the single electron intensity as significant discrepancies can occur when quantifying STEM images with different methods. To account for the detector response, we first image the detector using very low beam currents (∼8 fA), and subsequently model the interval between consecutive single electrons events. We find that single electrons striking the detector present a wide distribution of intensities, which we show is not described by a simple function. Further, we present a method to accurately account for the electrons within the incident probe when conducting quantitative imaging. The role detector settings play on determining the single electron intensity is also explored. Finally, we extend our analysis to describe the response of the detector to multiple electron events within the dwell interval of each pixel. [ABSTRACT FROM AUTHOR]

Abstract: We report the development of revolving scanning transmission electron microscopy – RevSTEM – a technique that enables characterization and removal of sample drift distortion from atomic resolution images without the need for a priori crystal structure information. To measure and correct the distortion, we acquire an image series while rotating the scan coordinate system between successive frames. Through theory and experiment, we show that the revolving image series captures the information necessary to analyze sample drift rate and direction. At atomic resolution, we quantify the image distortion using the projective standard deviation, a rapid, real-space method to directly measure lattice vector angles. By fitting these angles to a physical model, we show that the refined drift parameters provide the input needed to correct distortion across the series. We demonstrate that RevSTEM simultaneously removes the need for a priori structure information to correct distortion, leads to a dramatically improved signal-to-noise ratio, and enables picometer precision and accuracy regardless of drift rate. [Copyright &y& Elsevier]

Abstract: The measurement of accurate and precise structure factors and Debye Waller (DW) factors by quantitative convergent beam electron diffraction (QCBED) permits experimental determination of the electron density distribution and probing of interatomic bonding in crystals. The three QCBED methods used successfully for high precision measurements of low order structure factors to date, namely the zone axis pattern (ZAP) method, the excited row ER method and the multi-beam off-zone axis (MBOZA) technique, differ from each other regarding the crystal orientation relative to the incident electron beam. Consequently, the details of their respective dispersion surface representations differ regarding the number, relative amplitudes and phases of excited Bloch wave branches. Under the same experimental setup conditions, the factors most important to the degree of accuracy and precision achievable in electron density determination for crystals with QCBED methods ultimately depend on the sensitivity of the excited Bloch wave branches and the resultant contrast in the respective CBED patterns to changes in both structure and DW factors. In general, a QCBED pattern will be more sensitive to changes in both structure and DW factor, if it contains more and stronger excited Bloch wave branches, as dynamic interactions of the Bloch waves increase the sensitivity of the pattern. In this work we analyzed Bloch wave excitation and dispersion surfaces for the three most popular QCBED methods. The analysis indicates, that the QCBED patterns obtained using the MBOZA orientation generally contain more and stronger excited Bloch wave branches. Hence, MBOZA diffraction patterns are more sensitive than the ZAP and the ER patterns to changes in both DW and structure factors and therefore allow in differences to the other two methods simultaneous refinements effectively and robustly. [Copyright &y& Elsevier]

Low order structure and Debye–Waller (DW) factors for tetragonal L10-ordered γ-TiAl were measured simultaneously using quantitative convergent beam electron diffraction. The high precision and accuracy (largest error <0.5%) measurements allowed the construction of charge density difference maps from full sets of structure and DW factors, suitable for validation of first principles density functional theory (DFT) calculation results. Comparison of the experimentally determined charge density distribution with theoretical DFT predictions shows excellent qualitative agreement in this study. The three-dimensional charge density representations indicate a large electron charge localisation centred about the tetrahedral site at ¼, ¼, ¼, which is coordinated by two Ti atoms at 0, 0, 0 and ½, ½, 0 and two Al atoms at ½, 0, ½ and 0, ½, ½, respectively. Compared to experimental data, the DFT calculations based on full-potential linearised augmented plane wave (LAPW) method (implemented in WIEN2K) were found to quantitatively overestimate charge density between Ti–Ti second nearest neighbour atoms. Moreover, the results from the DFT method based on the projector-augmented wave (PAW) method and a plane wave basis set (implemented in VASP) were found to differ appreciably from both the experimental and LAPW-DFT results, implying that the PAW approach may not accurately describe the bonding in the intermetallic systems with 3 d electrons, such as γ-TiAl. [ABSTRACT FROM PUBLISHER]

The article discusses the study that measures Debye-Waller (DW) factors and low-order electron diffraction and X-ray diffraction structure factors for L10-ordered palladized iron (FePd). A multi-beam near-zone-axis quantitative convergent-beam electron diffraction (QCBED) method measured the DW factors and several low-order structure factors. It reveals that magnetic field of the L10-ordered γ1-FePd affects the intensity distribution in CBED patterns.

Abstract: Cu3Sn phase with the D019 structure is observed in Cu–Sn alloy by transmission electron microscopy. The structure is determined by electron diffraction, high-resolution transmission electron microscopy and high-angle annular dark-field imaging techniques. To the best of our knowledge this structure has not been reported before in Cu3Sn compounds. Transmission electron microscopy revealed high-density antiphase boundaries lying on the planes with translation vectors of in the D019 Cu3Sn. [Copyright &y& Elsevier]

Abstract: The accuracy of maximum entropy reconstruction of Z-contrast STEM images has been evaluated with the effects of experimental variables and noise taken into account by the means of image simulation. As the specimen contains atom species of greatly different atomic numbers, special attention is given to the reliability of the position and composition of lighter atoms that are determined from Z-contrast images in the presence of heavier atoms. When the noise is moderate (SNR >2.5), the position of atom columns can be measured within an accuracy of 0.03nm. With a higher signal-to-noise ratio (SNR >5) the composition of lighter atoms can be resolved reliably from the Z-contrast images. However, when image noise increases, the relative intensity of lighter atoms may deviate from the actual value in the specimen object function. [Copyright &y& Elsevier]

Thermoelectric materials and magnetocaloric materials are promising candidates for solid-state refrigeration applications. The combination of thermoelectric and magnetocaloric effects could potentially lead to more efficient refrigeration techniques. We designed and successfully synthesized Gd/YbAl 3 composites using a YbAl 3 matrix with good low-temperature thermoelectric performance and Gd microspheres with a high magnetocaloric performance, using a sintering condition of 750 °C and 50 MPa. Using aberration-corrected scanning transmission electron microscopy (STEM), it was discovered that the heterointerface between Gd and YbAl 3 is composed of five sequential interfacial layers: GdAl 3 , GdAl 2 , GdAl, Gd 3 Al 2 , and Gd 3 Al. The diffusion of Al atoms plays a crucial role in the formation of these interfacial layers, while Yb or Gd do not participate in the interlayer diffusion. This work provides the essential structural information for further optimizing and designing high-performance composites for thermoelectric-magnetocaloric hybrid refrigeration applications. Image 1 • Synthesized Gd/YbAl 3 composite for hybrid thermoelectric-magnetocaloric refrigeration. • Identified interfacial structure and defect structure at Gd/YbAl 3 inteface using atomic resolution STEM and EDS. • Revealed interfacial chemical reaction mechanism dominated by Al diffusion. [ABSTRACT FROM AUTHOR]

Understanding and controlling the transformations of transition metal dichalcogenides (TMDs) from amorphous precursors into two‐dimensional (2D) materials is important for guiding synthesis, directing fabrication, and tailoring functional properties. Here, the combined effects of thermal energy and electron beam irradiation are explored on the structural evolution of 2D MoS2 flakes through the thermal decomposition of a (NH4)2MoS4 precursor inside an ultrahigh vacuum (10−9 Torr) scanning transmission electron microscope (STEM). The influence of reaction temperature, growth substrate, and the initial precursor morphology on the resulting 2D MoS2 flake morphology, edge structures, and point defects are explored. Although thermal decomposition occurs extremely fast at elevated temperatures and is difficult to capture using current STEM techniques, electron beam irradiation can induce local transformations at lower temperatures, enabling direct observation and interpretation of critical growth steps including oriented attachment and transition from single‐ to multilayer structures at atomic resolution. An increase in the number of layers of the MoS2 flakes from island growth is investigated using electron beam irradiation. These findings provide insight into the growth mechanisms and factors that control the synthesis of few‐layer MoS2 flakes through thermolysis and toward the prospect of atomically precise control and growth of 2D TMDs. [ABSTRACT FROM AUTHOR]

Mixed‐halide perovskites show promising applications in tandem solar cells owing to their adjustable bandgap. One major obstacle to their commercialization is halide phase segregation, which results in large open‐circuit voltage deficiency and J‐V hysteresis. However, the ambiguous interplay between structural origin and phase segregation often results in aimless and unspecific optimization strategies for the device's performance and stability. An atomic scale is directly figured out the abundant Ruddlesden‐Popper anti‐phase boundaries (RP‐APBs) within a CsPbIBr2 polycrystalline film and revealed that phase segregation predominantly occurs at RP‐APB‐enriched interfaces due to the defect‐mediated lattice strain. By compensating their structural lead halide, such RP‐APBs are eliminated, and the decreasing of strain can be observed, resulting in the suppression of halide phase segregation. The present work provides the deciphering to precisely regulate the perovskite atomic structure for achieving photo‐stable mixed halide wide‐bandgap perovskites of high‐efficiency tandem solar cell commercial applications. [ABSTRACT FROM AUTHOR]

Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M‐N4) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M‐N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni‐N4‐O/C). The Ni‐N4‐O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) close to 100 % at −0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from −0.5 to −1.1 V. The superior CO2RR activity is due to the Ni‐N4‐O active moiety composed of a Ni‐N4 site with an additional oxygen atom that induces an axial traction effect. [ABSTRACT FROM AUTHOR]

Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M‐N4) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M‐N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni‐N4‐O/C). The Ni‐N4‐O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) close to 100 % at −0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from −0.5 to −1.1 V. The superior CO2RR activity is due to the Ni‐N4‐O active moiety composed of a Ni‐N4 site with an additional oxygen atom that induces an axial traction effect. [ABSTRACT FROM AUTHOR]

How to efficiently dissipate the heat of a large‐area hot source is an urgent problem to be solved in the thermal management field of electronic devices. Herein, multi‐stage planar thermoelectric coolers (TECs) oriented to the efficient planar heat dissipation for large‐area hot source are designed, and a comprehensive numerical analysis focusing on the cooling performance of the coolers for a heat source is performed by the finite‐element methods. The effect of input current, thickness of thermoelectric legs, stage numbers in heat transfer area, numbers of p–n pair in each stage, heat resistance between each stage, and contact status between heat sources and coolers are studied. The results show that high cooling performance of the coolers relies on an optimized input current, large thickness of thermoelectric legs, optimized stage number and number of p–n pair, and low heat resistance between each stage and between heat sources and coolers. The optimized multi‐stage planar TEC can realize a maximum cooling temperature difference of 8.2 K. This work indicates that the multi‐stage planar TECs can have potential application in thermal management of electronic devices. [ABSTRACT FROM AUTHOR]

Electrosynthesis of H2O2 has great potential for directly converting O2 into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical‐level H2O2 production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (FeSA‐NS/C). The newly‐developed FeSA‐NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H2O2 at a high current of 100 mA cm−2 with a record high H2O2 selectivity of 90 %. An accumulated H2O2 concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally‐designed catalytic active center with the atomic Fe site stabilized by three‐coordinated nitrogen atoms and one‐sulfur atom (Fe‐N3S‐C). It was further found that the replacement of one N atom with S atom in the classical Fe‐N4‐C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H2O2 electrosynthesis. [ABSTRACT FROM AUTHOR]

Electrosynthesis of H2O2 has great potential for directly converting O2 into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical‐level H2O2 production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (FeSA‐NS/C). The newly‐developed FeSA‐NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H2O2 at a high current of 100 mA cm−2 with a record high H2O2 selectivity of 90 %. An accumulated H2O2 concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally‐designed catalytic active center with the atomic Fe site stabilized by three‐coordinated nitrogen atoms and one‐sulfur atom (Fe‐N3S‐C). It was further found that the replacement of one N atom with S atom in the classical Fe‐N4‐C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H2O2 electrosynthesis. [ABSTRACT FROM AUTHOR]

A high density of grain boundaries can potentially increase structural materials' strength, but at the expense of losing the materials' strain hardening ability at high flow stress levels. However, endowing materials with grain size gradients and a high density of internal interfaces can simultaneously increase the strength and strain hardening ability. This applies particularly for through-thickness gradients of nanoscale interface structures. Here we apply a machining method that produces metals with nanoscale interface gradients. Conventional bulk plastic deformation such as rolling, a process applied annually to about 2 billion tons of material, aims to reduce the metal thickness. We have modified this process by introducing severe strain path changes, realized by leading the sheet through a U-turn while preserving its shape, an approach known as 'hard turning'. We applied this process at both room temperature and 77 K to a NiCrCo medium entropy alloy. Micropillar compression was conducted to evaluate the mechanical response. After hard turning at room temperature, the surface microstructure obtained a ∼50% increase in yield stress (0.9 GPa) over the original state with homogeneous grain size (0.4 GPa), but the initial strain hardening rate did not show significant improvement. However, after hard turning at 77 k, the gradient nanolaminate structure tripled in yield stress and more than doubled its initial strain hardening rate. The improvements were achieved by introducing a specific microstructure that consists of gradient nanolaminates in the form of nanospaced twins and martensite in the face center cubic (fcc) phase. This microstructure was formed only at cryogenic temperature. It was found after turning at room temperature that only nanospaced twins were present in the fcc phase inside nanolaminates that had formed at the surface. The origin of the enhanced strain hardening mechanism was studied. Joint density functional theory (DFT) and axial next nearest neighbor Ising (ANNNI) models were used to explain the temperature-dependent phase formation of the NiCrCo nanolaminate at the surface of the hard-turned material. Image 1 [ABSTRACT FROM AUTHOR]

Abstract A simplified aging treatment yielded microstructural features in Ni-based alloy that produced strengthening behavior normally associated with more complex thermal processing. Specifically, a time series of 800 °C heat treatments was used to study the evolution of grain boundary carbides and γ' precipitates and the corresponding hardness, tensile strength, and creep resistance. These analyses and computational thermodynamic calculations revealed that a 4-hour aging treatment produced appropriately sized and uniformly distributed coherent γ' precipitates and the desired Cr-rich carbides like those formed during the conventional two-step heat treatment. Accordingly, the former heat treatment produced targeted typical strength levels for this alloy. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Co magnetic films are widely used in high-frequency magnetic recording and vertical magnetic recording due to their high saturation magnetization and magnetocrystalline anisotropy. In this work, ferromagnetic Co magnetic films were prepared on copper substrate by vacuum evaporation combined with heat treatment (H2 atmosphere), to investigate the impact of film thickness and annealing temperature on microstructure and magnetic properties. The results show that with the increase in annealing temperature, the Co thin film physical phase does not change significantly, the crystallinity increases, and the grain size increases, which is consistent with the results obtained from the SEM morphology map of the sample surface, leading to an increase in coercivity. By annealing experiments (atmospheric atmosphere) on Co magnetic films with and without an Al protective layer, as shown by scanning electron microscopy microscopic characterization results, it was verified that the Al layer can protect the inner Co layer from oxidation. As the film thickness increases from 10 to 300 nm, the magnetic properties of Co films change significantly. The saturation magnetization gradually increases from 0.89 to 5.21 emu/g, and the coercivity increases from 124.3 to 363.8 Oe. The remanence ratio of the 10 nm magnetic film is 0.82, which is much higher than the film remanence ratio of 0.46 at 50 nm. This is because when the thickness of the film is between 10 and 50 nm, the magnetic moments partially deviate from the in-plane direction, and the out-of-plane component reduces the film remanence ratio. This study shows that optimizing annealing temperature and film thickness can effectively control the structure and magnetic properties of Co magnetic films, which is of great significance for the development of the magnetic recording field. [ABSTRACT FROM AUTHOR]

Designing hydrogen evolution reaction (HER) electrocatalysts for facilitating its sluggish adsorption kinetics is crucial in generating green hydrogen via sustainable water electrolysis. Herein, a high‐performance ultra‐low Ruthenium (Ru) catalyst is developed consisting of atomically‐layered Ru nanoclusters with adjacent single Ru sites, which executs a bridging‐Ru‐H activation strategy to kinetically accelerate the HER elementary steps. Owing to its optimal electronic structure and unique adsorption configuration, the hybrid Ru catalyst simultaneously displayed a drastically reduced overpotential of 16 mV at 10 mA cm−2 as well as a low Tafel slope of 35.2 mV dec−1 in alkaline electrolyte. When further coupled with a commercial IrO2 anode catalyst, the ensembled anion‐exchange membrane water electrolyzer achievs a current density of 1.0 A cm−2 at a voltage of only 1.70 Vcell. In situ spectroscopic analysis verified that Ru single atom and atomically‐layered Ru nanoclusters in the hybrid materials play a critical role in facilitating water dissociation and weakening *H adsorption, respectively. Theoretical calculations further elucidate the underlaying mechanism, suggesting that the dissociated proton at the single atom Ru site orients itself adjacently with Ru nanoclusters in a bridged structure through targeted charge transfer, thus promoting Volmer‐Heyrovsky dynamics and boosting the HER activity. [ABSTRACT FROM AUTHOR]

Cu‐based catalysts have been widely applied in electroreduction of carbon dioxide (CO2ER) to produce multicarbon (C2+) feedstocks (e.g. C2H4). However, the high energy barriers for CO2 activation on the Cu surface is a challenge for a high catalytic efficiency and product selectivity. Herein, we developed an in situ *CO generation and spillover strategy by engineering single Ni atoms on a pyridinic N‐enriched carbon support with a sodalite (SOD) topology (Ni‐SOD/NC) that acted as a donor to feed adjacent Cu nanoparticles (NPs) with *CO intermediate. As a result, a high C2H4 selectivity of 62.5 % and an industrial‐level current density of 160 mA cm−2 at a low potential of −0.72 V were achieved. Our studies revealed that the isolated NiN3 active sites with adjacent pyridinic N species facilitated the *CO desorption and the massive *CO intermediate released from Ni‐SOD/NC then overflowed to Cu NPs surface to enrich the *CO coverage for improving the selectivity of CO2ER to C2H4. [ABSTRACT FROM AUTHOR]

Cu‐based catalysts have been widely applied in electroreduction of carbon dioxide (CO2ER) to produce multicarbon (C2+) feedstocks (e.g. C2H4). However, the high energy barriers for CO2 activation on the Cu surface is a challenge for a high catalytic efficiency and product selectivity. Herein, we developed an in situ *CO generation and spillover strategy by engineering single Ni atoms on a pyridinic N‐enriched carbon support with a sodalite (SOD) topology (Ni‐SOD/NC) that acted as a donor to feed adjacent Cu nanoparticles (NPs) with *CO intermediate. As a result, a high C2H4 selectivity of 62.5 % and an industrial‐level current density of 160 mA cm−2 at a low potential of −0.72 V were achieved. Our studies revealed that the isolated NiN3 active sites with adjacent pyridinic N species facilitated the *CO desorption and the massive *CO intermediate released from Ni‐SOD/NC then overflowed to Cu NPs surface to enrich the *CO coverage for improving the selectivity of CO2ER to C2H4. [ABSTRACT FROM AUTHOR]

Defects formed during chemical vapor deposition (CVD) of two-dimensional (2D) transition metal dichalcogenides (TMDs) currently limit their quality and optoelectronic properties. Effective synthesis and processing strategies to suppress defects and enhance the quality of 2D TMDs are urgently needed to enable next generation optoelectronic devices. In this work, isoelectronic doping is presented as a new strategy to form stable alloys and suppress defects and enhance photoluminescence (PL) in CVD-grown TMD monolayers. The isoelectronic substitution of W atoms for Mo atoms in CVD-grown monolayers of Mo1- x W x Se2 (0 < x < 0.18) is shown to effectively suppress Se vacancy concentration by 50% compared to those found in pristine MoSe2 monolayers, resulting in a decrease in defect-mediated nonradiative recombination, ≈10 times more intense PL, and an increase in the carrier lifetime by a factor of 3. Theoretical predictions reveal that isoelectronic W alloying to form Mo1- x W x Se2 monolayers raises the energy of deep level defects in MoSe2 to enable faster quenching, which is confirmed by low temperature (4-125 K) PL from defect-related localized states. Isoelectronic substitution therefore appears to be a promising synthetic method to control the heterogeneity of 2D TMDs to realize the scalable production of high performance optoelectronic and electronic devices. [ABSTRACT FROM AUTHOR]

The development of highly efficient robust electrocatalysts with low overpotential and industrial‐level current density is of great significance for CO2 electroreduction (CO2ER), however the low proton transport rate during the CO2ER remains a challenge. Herein, a porous N‐doped carbon nanofiber confined with tin‐nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO2ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec−1. In a flow cell, an industrial‐level CO partial current density of 100.6 mA cm−2 is achieved. In situ spectroscopic analysis unveil the isolated SnN site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate‐determining step for CO2ER. Theoretical calculations validate pyrrolic N atom adjacent to the SnN active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO2ER kinetics. A Zn‐CO2 battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm−2 and long‐term stability. [ABSTRACT FROM AUTHOR]

Artificially tilted multilayer thermoelectric devices (ATMTDs) have attracted growing attention due to their ease in miniaturization and high flexibility in device design. However, most of these devices are inefficient due to the lack of effective strategy to optimize their material matching and geometrical configurations. Herein, a high-throughput optimization approach is employed to screen high-performance Bi 2 Te 2.7 Se 0.3 -based ATMTDs from a material genome database covering 230 kinds of candidates. 14 kinds of ATMTDs are found to have ZT zx ,max values exceeding 0.3 and tilt angles greater than 15°. Bi 0.1 Sb 1.9 Te 3 /Bi 2 Te 2.7 Se 0.3 ATMTD is screened out and fabricated because of its excellent transverse figure of merit, large tilt angle, and good interface compatibility. Consequently, transverse figure of merit over 0.3, thermal sensitivity greater than 0.11 mV·K−1, and power density up to 1.1 kW·m−2 are recorded in Bi 0.1 Sb 1.9 Te 3 /Bi 2 Te 2.7 Se 0.3 ATMTD. This indicates that ATMTDs have great potential for application in the fields of temperature detection and power generation. [ABSTRACT FROM AUTHOR]

Here we report a transparent dual‐phase ZnO·2.7Al2O3 ceramic. The composite is pore‐free and consists of thin nanosheets with a spinel phase and a hexagonal phase, while the two phases match closely in both lattice and refractive index. Such features result in excellent optical transmittance (maximum value >80% in the visible spectrum) at comparable phase volume. This work may provide a new thought for the rational structural design of optical nanocomposites. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts show great promise as non‐precious electrocatalysts for CO2 electroreduction reaction (CO2ER). However, it is still challenging to gain a fundamental understanding of the complicated dynamic behavior of CO2 activation to achieve high product selectivity. Herein, the authors report an unusual iron single‐atom catalyst, containing atomically dispersed Fe–N4 species and Fe3C nanoparticles (NPs) (Fe3C|Fe1N4). Having a fragmental‐rock‐shaped nanocarbon architecture, isolated Fe–N4 sites uniformly disperse with adjacent Fe3C NPs (<30 nm) in a carbon matrix. Benefiting from the strong coupling effect between Fe3C and Fe1N4 and unique spatial nanostructure, Fe3C|Fe1N4 displays exceptional CO2ER activity with a low onset potential of −0.3 V and high Faradaic efficiency of 94.6% at −0.5 V for CO production, acting as one of the most active Fe–N–C catalysts and even exceeding most other carbon supported non‐precious metal NPs. Experimental observations discover that the excellent CO2ER activity of Fe3C|Fe1N4 catalyst is attributable to the presence of Fe3C NPs that optimizes JCO of the coexisted Fe–N4 active sites. In situ attenuated total reflectance‐Fourier transform infrared analysis and theoretical calculations reveal that the Fe3C NPs strengthen the adsorption of CO2 on the isolated Fe–N4 sites to accelerate the formation of *COOH intermediate, and hence enhance the whole CO2ER performance. [ABSTRACT FROM AUTHOR]

Lithium metal is an ideal anode for next‐generation high‐energy‐density batteries. However, lithium dendrite growth has impeded its commercial application. Herein, fabricating Li‐based ultrathin alloys with electronic localization and high surface work function via depositing Bi, Al, or Au metals on the surface of copper foil for in situ alloying with lithium is proposed. It is discovered that the electronic localization can induce self‐smoothing effect of Li ions, as a result, significantly suppressing the growth of dendritic lithium. Meanwhile, the high surface work function can effectively alleviate side reactions between the electrolyte and lithium. With the as‐obtained ultrathin alloys as anodes, excellent cycling performance is achieved. The half cells run stably after more than 120 cycles under high capacity of 4 mAh cm−2. The S||Bi/Cu‐Li full cell delivers a specific capacity of 736 mAh g−1 after 200 cycles. This work provides a new strategy for fabricating long‐life and high‐capacity lithium batteries. [ABSTRACT FROM AUTHOR]

Sluggish water dissociation kinetics in the Volmer step on platinum‐free electrocatalysts limits the development of hydrogen evolution from economical water‐alkali electrolyser. Herein, an unusual nanosheets electrocatalyst of molybdenum‐doped cobalt selenide with selenium vacancy encapsulated within N‐doped carbon matrix (Mo‐Co0.85SeVSe/NC) for efficient hydrogen evolution reaction (HER) is reported. Benefiting from the optimized electronic structure, this Mo‐Co0.85SeVSe/NC nanosheet exhibits a high catalytic activity for alkaline HER, achieving the current densities of 10 and 200 mA cm−2 at low overpotentials of 151 and 275 mV, respectively. These results are among the highest catalytic activities in respect with all previously reported transition‐metal‐selenide based HER electrocatalysts. The combined in situ spectroscopic and theoretical studies reveal that the incorporation of Mo‐dopant and Se vacancies into Co0.85Se efficiently enhances electron transfer from Mo to Co atom through the bridging Se atom, leading to the formation of enriched electronic Co site to accelerate water dissociation, eventually facilitating the overall alkaline HER process. An integrated Zn‐H2O battery with a Mo‐Co0.85SeVSe/NC cathode is developed to further demonstrate the potential applications of the newly developed HER catalyst. [ABSTRACT FROM AUTHOR]

Sluggish water dissociation kinetics in the Volmer step on platinum‐free electrocatalysts limits the development of hydrogen evolution from economical water‐alkali electrolyser. Herein, an unusual nanosheets electrocatalyst of molybdenum‐doped cobalt selenide with selenium vacancy encapsulated within N‐doped carbon matrix (Mo‐Co0.85SeVSe/NC) for efficient hydrogen evolution reaction (HER) is reported. Benefiting from the optimized electronic structure, this Mo‐Co0.85SeVSe/NC nanosheet exhibits a high catalytic activity for alkaline HER, achieving the current densities of 10 and 200 mA cm−2 at low overpotentials of 151 and 275 mV, respectively. These results are among the highest catalytic activities in respect with all previously reported transition‐metal‐selenide based HER electrocatalysts. The combined in situ spectroscopic and theoretical studies reveal that the incorporation of Mo‐dopant and Se vacancies into Co0.85Se efficiently enhances electron transfer from Mo to Co atom through the bridging Se atom, leading to the formation of enriched electronic Co site to accelerate water dissociation, eventually facilitating the overall alkaline HER process. An integrated Zn‐H2O battery with a Mo‐Co0.85SeVSe/NC cathode is developed to further demonstrate the potential applications of the newly developed HER catalyst. [ABSTRACT FROM AUTHOR]

Electrocatalytic reduction of CO2 (CO2RR) to value‐added chemicals is of great significance for CO2 utilization, however the CO2RR process involving multi‐electron and proton transfer is greatly limited by poor selectivity and low yield. Herein, We have developed an atomically dispersed monovalent zinc catalyst anchored on nitrogenated carbon nanosheets (Zn/NC NSs). Benefiting from the unique coordination environment and atomic dispersion, the Zn/NC NSs exhibit a superior CO2RR performance, featuring a high current density up to 50 mA cm−2 with an outstanding CO Faradaic efficiency of ≈95 %. The center ZnI atom coordinated with three N atoms and one N atom that bridges over two adjacent graphitic edges (Zn‐N3+1) is identified as the catalytically active site. Experimental results reveal that the twisted Zn‐N3+1 structure accelerates CO2 activation and protonation in the rate‐determining step of *CO2 to *COOH, while theoretical calculations elucidate that atomically dispersed Zn‐N3+1 moieties decrease the potential barriers for intermediate COOH* formation, promoting the proton‐coupled CO2RR kinetics and boosting the overall catalytic performance. [ABSTRACT FROM AUTHOR]

Electrocatalytic reduction of CO2 (CO2RR) to value‐added chemicals is of great significance for CO2 utilization, however the CO2RR process involving multi‐electron and proton transfer is greatly limited by poor selectivity and low yield. Herein, We have developed an atomically dispersed monovalent zinc catalyst anchored on nitrogenated carbon nanosheets (Zn/NC NSs). Benefiting from the unique coordination environment and atomic dispersion, the Zn/NC NSs exhibit a superior CO2RR performance, featuring a high current density up to 50 mA cm−2 with an outstanding CO Faradaic efficiency of ≈95 %. The center ZnI atom coordinated with three N atoms and one N atom that bridges over two adjacent graphitic edges (Zn‐N3+1) is identified as the catalytically active site. Experimental results reveal that the twisted Zn‐N3+1 structure accelerates CO2 activation and protonation in the rate‐determining step of *CO2 to *COOH, while theoretical calculations elucidate that atomically dispersed Zn‐N3+1 moieties decrease the potential barriers for intermediate COOH* formation, promoting the proton‐coupled CO2RR kinetics and boosting the overall catalytic performance. [ABSTRACT FROM AUTHOR]

Artificially-tilted multilayer transverse thermoelectric devices (ATMTTDs) have a large degree of design freedom, which is convenient for designing devices for different working conditions. However, evaluation and preparation of ATMTTDs has generally been based on trial and error, and coherent performance optimization strategies for different ATMTTDs applications is still lacking. Here, the relationship between performance evaluation indicators, transverse thermoelectric properties, and geometric structure parameters of ATMTTDs has been established via theoretical calculation and experimental verification. The results show that the tilt angle (θ) has a key effect on the transverse thermoelectric properties of ATMTTDs. The optimal transverse thermoelectric figure of merit, power factor, and Seebeck coefficient of Ni/Bi 0.5 Sb 1.5 Te 3 (BST) ATMTTDs are theoretically predicted at tilt angles of 11°, 21°, and 45°, respectively. Ni/BST ATMTTDs have been fabricated and the experimental results demonstrated that a maximum power generation efficiency of 1.01% and maximum effective refrigeration temperature difference of 0.4 K are reached at θ = 11°, maximum output power density of 411 W/m2 is obtained at θ = 21°, and a maximum response sensitivity of 420 μV/K is achieved at θ = 45°, which is in good agreement with theoretical predictions. This work provides theoretical guidance for manufacturing ATMTTDs for different applications. • Performance optimization strategy of ATMTTDs was established and verified. • Tilt angle has a key effect on the transverse thermoelectric properties. • High-performance Ni/Bi 0.5 Sb 1.5 Te 3 ATMTTDs were fabricated for verification. [ABSTRACT FROM AUTHOR]

Developing single‐atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO2 reduction reaction (CO2RR) still remains a great challenge. Herein, a porous NiNC catalyst containing atomically dispersed NiN4 sites and nanostructured zirconium oxide (ZrO2@Ni‐NC) synthesized via a post‐synthetic coordination coupling carbonization strategy is reported. The as‐prepared ZrO2@Ni‐NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec−1 in electrochemical CO2RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO2@Ni‐NC far exceeds those of recently developed state‐of‐the‐art CO2RR electrocatalysts based on NiN moieties anchored carbon. In a flow cell, ZrO2@Ni‐NC delivers a current density of 200 mA cm−2 with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated NiN4 species act as real active sites to drive the CO2RR reaction and that the nanostructured ZrO2 largely accelerates the protonation process of *CO2− to *COOH intermediate, thus significantly reducing the energy barrier of this rate‐determining step and boosting whole catalytic performance. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials have great potential for waste-energyrecycling and solid-state cooling. Their conversion efficiency has attracted huge attention to the development of TE devices, and largely depends on the thermal and electrical transport properties. Magnetically enhanced thermoelectrics open up the possibility of making thermoelectricity a future leader in sustainable energy development and offer an intriguing platform for both fundamental physics and prospective applications. In this review, state-of-the-art TE materials are summarized from the magnetism point of view, via diagrams of the charges, lattices, orbits and spin degrees of freedom. Our fundamental knowledge of magnetically induced TE effects is discussed. The underlying thermo–electro–magnetic merits are discussed in terms of superparamagnetism- and magnetic-transition-enhanced electron scattering, field-dependent magnetoelectric coupling, and the magnon- and phonon-drag Seebeck effects. After these topics, we finally review several thermal–electronic and spin current-induced TE materials, highlight future possible strategies for further improving ZT, and also give a brief outline of ongoing research challenges and open questions in this nascent field. [ABSTRACT FROM AUTHOR]

In this paper, we found that (NH4)2V4O9 undergoes an electrochemical activation process in the first charging process at ∼1.4 V (vs. Zn2+/Zn), leading to a significant improvement of capacity and cycling stability. The activated vanadium oxides delivered a high specific capacity of 477 mA h g−1 at 50 mA g−1 and outstanding cycling stability with 97.7% capacity retention after 5000 cycles at 15 A g−1. [ABSTRACT FROM AUTHOR]

Thermoelectric materials can directly convert electrical energy and thermal energy by regulating carrier and phonon transport under electrical and thermal fields. However, further enhancement of thermoelectric properties is hindered by limited available methods that can synergistically tune transport properties. Here, multiferroic BiFeO 3 nanoparticles with spontaneous electrical and magnetic polarization are synthesized and incorporated into p -type Bi 0.5 Sb 1.5 Te 3 , to probe the impact of simultaneous local electrical field and magnetic field on the transport properties of the BiFeO 3 /Bi 0.5 Sb 1.5 Te 3 nanocomposites. The BiFeO 3 /Bi 0.5 Sb 1.5 Te 3 atomic-resolution interfacial structure is revealed using aberration-corrected scanning transmission electron microscopy. The selective reaction of Sb cations leads to reduced carrier concentration and decreased electrical conductivity. The Seebeck coefficient is enhanced by additional scattering from local electrical and magnetic field. Phonon scattering is boosted by the nanostructures from interfacial reaction and local lattice distortion caused by the polarization. As a result, the ZT values and the cooling performance are improved by 9% and 31% for the nanocomposites, respectively. [Display omitted] ● Multiferroic BiFeO 3 nanoparticles were incorporated into Bi 0.5 Sb 1.5 Te 3 matrix to improve thermoelectric properties. ● Electric polarization of the embedded BiFeO 3 nanoparticles were confirmed using atomic resolution STEM. ● The BiFeO 3 / Bi 0.5 Sb 1.5 Te 3 interfacial structure was thoroughly investigated using atomic resolution STEM. ● Improved thermoelectric properties and cooling performance were obtained for the nanocomposites. [ABSTRACT FROM AUTHOR]

Graphene, with unique mechanical and electrical properties, offers diverse application opportunities from beyond Moore’s nano-electronics to water filtration. However, accomplishing these relies on cleaning and processing large areas of supported and suspended graphene sheets. Here, we demonstrate the use of an Ar cluster ion beam as a versatile tool for graphene cleaning, defect engineering, and nanopore fabrication. In-situ and ex-situ characterization techniques were utilized in combination with first principles molecular dynamics, to highlight the differences in processing of the supported and suspended graphene samples. In this work, we monitor interaction of the Ar cluster ion beam with graphene as a function of ion dose with in-situ secondary ion mass spectrometry (SIMS), as well as ex-situ Raman spectroscopy measurements. Scanning transmission electron microscopy (STEM) results confirm that the Ar cluster ion beam can form nanopores in the suspended graphene; while the basal plane of graphene remains intact maintaining the lattice structure. Finally, Scanning Electron Microscopy (SEM) image analysis of the irradiated samples allows quantitative tracking of pore areas and their distribution as a function of ion dose. This study highlights the flexibility of the Ar cluster ion beam in 2D material processing, and offers insights into Ar beam interaction with graphene. [ABSTRACT FROM AUTHOR]

Mg alloys offer potential advantages over conventional biomedical implant materials because of their biodegradability and biocompatibility, but could be limited by their poor mechanical properties. In this study, laser shock peening (LSP), a surface processing technique, was applied to improve the mechanical properties of the AZ31B magnesium (Mg) alloy. It was demonstrated that LSP increased the hardness and yield strength of the Mg alloy. Due to the hardening, LSP significantly improved the wear resistance and fatigue performance of the Mg alloy. In addition, immersion tests carried out in cell culture medium revealed that LSP did not significantly increase Mg 2+ release and weight loss. Furthermore, an in vitro cell culture study showed that the LSP-treated samples have cell-compatibility comparable to untreated samples. Thus, the LSP technique could, with further study, advance the clinical utility of Mg alloys in the orthopedic field. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanide (Ln) group elements have been attracting considerable attention owing to the distinct optical properties. The crystal‐field surroundings of Ln ions in the host materials can determine their energy level splitting, which is of vital importance to tailor their optical properties. 2D MoS2 single crystals were utilized as the host material to embed Eu3+ and energy‐level splitting was achieved for tuning its photoluminescence (PL). The high anisotropy of the 2D host materials makes them distort the degenerate orbitals of the Ln ions more efficiently than the symmetrical bulk host materials. A significant red‐shift of the PL peak for Eu3+ was observed. The strategy for tailoring the energy level splitting of Ln ions by the highly designable 2D material crystal field provides a new method to extend their optical properties. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanide (Ln) group elements have been attracting considerable attention owing to the distinct optical properties. The crystal‐field surroundings of Ln ions in the host materials can determine their energy level splitting, which is of vital importance to tailor their optical properties. 2D MoS2 single crystals were utilized as the host material to embed Eu3+ and energy‐level splitting was achieved for tuning its photoluminescence (PL). The high anisotropy of the 2D host materials makes them distort the degenerate orbitals of the Ln ions more efficiently than the symmetrical bulk host materials. A significant red‐shift of the PL peak for Eu3+ was observed. The strategy for tailoring the energy level splitting of Ln ions by the highly designable 2D material crystal field provides a new method to extend their optical properties. [ABSTRACT FROM AUTHOR]

In article number 1603850, Kai Xiao and co‐workers present a new strategy for suppressing chalcogen defects in 2D transition metal dichalcogenide monolayers, specifically MoSe2 monolayers. Isoelectronic tungsten (W) alloying during monolayer synthesis results in Mo1−xWxSe2. Defect suppression is essential for the development of high performance optoelectronic and electronic devices. [ABSTRACT FROM AUTHOR]

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. However, controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with ab initio molecular dynamics simulations to examine the ion behavior in the GBs of CH3NH3PbI3 perovskite films. This combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. This work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl− ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices. [ABSTRACT FROM AUTHOR]

The effect of support on electrocatalytic activity of Cu nanoparticles (NPs) towards CO 2 electroreduction to hydrocarbon fuels (CH 4 and C 2 H 4 ) is investigated for three types of nanostructured carbons: single wall carbon nanotubes (SWNT), reduced graphene oxide (RGO) and onion-like carbon (OLC). Cu/SWNT, Cu/RGO and Cu/OLC composite catalysts are synthesized and characterized by X-ray diffraction analysis, transmission electron microscopy and electrochemical surface area measurements. Electrocatalytic activities of the synthesized materials, as measured in an electrochemical cell connected to a gas chromatograph, are compared to that of Cu NPs supported on Vulcan carbon. All four catalysts demonstrate higher activity towards C 2 H 4 generation vs CH 4 , with production of the latter mostly suppressed on Cu NPs supported on nanostructured substrates. Onset potentials for C 2 H 4 vs CH 4 generation demonstrate 200 mV positive shifts for Cu/SWNT, Cu/RGO, and Cu/OLC catalysts. The Cu/OLC catalyst is found to be superior to the other two nanostructured catalysts in terms of stability, activity and selectivity towards C 2 H 4 generation. Its faradaic efficiency reached 60% at −1.8 V vs Ag/AgCl. The enhanced stability and activity of the Cu/OLC catalyst can be attributed to the unique catalyst design, wherein a shell of OLC surrounds the Cu NPs. Such a configuration enables the outer layer to act as a filter that protects the Cu surface from adsorption of undesirable species, enhances its electrocatalytic performance, and improves its viability in CO 2 electroreduction reaction. The enhanced selectivity of the Cu/OLC catalyst towards the C 2 H 4 production is most likely related to the enhanced electrocatalytic activity of the OLC support towards the CO 2 electroreduction to CO. Higher CO surface concentration from CO 2 electroreduction on the OLC support, rather than a greater number of available sites for CO dimerization, likely originated this behavior. CO molecules generate on surfaces of OLCs, dimerize on Cu NP (100) planes, and, subsequently, yield additional C 2 H 4 molecules. Both the reduction of the CO 2 to CO on the surface of OLCs and reduction of “extra” CO molecules to C 2 H 4 on the surface of Cu NPs are expected to lead to an increase in the local pH, which is also beneficial for the C 2 H 4 production. [ABSTRACT FROM AUTHOR]

The working temperature range of magnetic refrigeration (MR) is severely limited by the narrow range of magnetic entropy change (Δ S M) of magnetocaloric (MC) materials, which especially hinders MR applications near room temperature. Here, high-entropy La(Fe, Si) 13 based MC materials with increasing number of equimolar transition metal elements such as Mn, Co, Ni, and Cr occupying Fe sites were synthesized using arc melting and annealing, to stabilize the La(Fe, Si) 13 phase, and to increase δ F W H M. Atomic resolution aberration corrected scanning transmission electron microscopy and elemental mapping confirmed that the doped transition metal elements uniformly occupy the Fe sites. Due to enhanced configuration entropy, the high entropy alloy has achieved La(Fe, Si) 13 single phase structure. Magnetic property measurements reveal that the working temperature range of the high entropy alloy has increased by 141.3%. This work provides a new method to design novel MC materials for better stability and larger temperature range. We designed a new magnetic refrigeration material based on high entropy theory. Due to enhanced configuration entropy, the high entropy alloy has achieved La(Fe,Si) 13 single phase structure. Magnetic property measurements reveal that the working temperature range of the high entropy alloy has increased by 141.3%. This work provides a new method to design novel MC materials for better stability and larger temperature range. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel hafnium oxide (HfO2)-based ferroelectrics reveal full scalability and complementary metal oxide semiconductor integratability compared to perovskite-based ferroelectrics that are currently used in nonvolatile ferroelectric random access memories (FeRAMs). Within the lifetime of the device, two main regimes of wake-up and fatigue can be identified. Up to now, the mechanisms behind these two device stages have not been revealed. Thus, the main scope of this study is an identification of the root cause for the increase of the remnant polarization during the wake-up phase and subsequent polarization degradation with further cycling. Combining the comprehensive ferroelectric switching current experiments, Preisach density analysis, and transmission electron microscopy (TEM) study with compact and Technology Computer Aided Design (TCAD) modeling, it has been found out that during the wake-up of the device no new defects are generated but the existing defects redistribute within the device. Furthermore, vacancy diffusion has been identified as the main cause for the phase transformation and consequent increase of the remnant polarization. Utilizing trap density spectroscopy for examining defect evolution with cycling of the device together with modeling of the degradation results in an understanding of the main mechanisms behind the evolution of the ferroelectric response. [ABSTRACT FROM AUTHOR]

NaZn 13 -type La(Fe,Si) 13 alloys are one of the most promising magnetocaloric materials near room temperature. However, the impact of lanthanide doping on their magnetocaloric properties has not been thoroughly investigated. Here, a series of Gd-doped La 1− x Gd x Fe 11.5 Si 1.5 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) alloys were designed and synthesized by arc melting and annealing. The microstructure of different phases and their influence on magnetic properties were investigated. The Gd doping at La sites was confirmed by the lattice contraction revealed by X-ray diffraction and elemental mapping analysis. After saturation at around x = 0.1, extra Gd leads to formation of Gd-rich Gd 2 Fe 16 Si phase. Moreover, doping of extra Gd inhibits the formation of La(Fe,Si) 13 phase, resulting in significantly increased amount of the impurity phases (α-Fe and LaFeSi phase). The change of microstructure and composition causes the magnetic transition to shift from first order to second order. Because of Gd doping, the Curie temperature of La 1− x Gd x Fe 11.5 Si 1.5 increases, and the maximum entropy change decreases. Understanding the effect of Gd on the microstructure and magnetic properties can help us develop more rare-earth-doped La(Fe, Si) 13 alloys. • The microstructure, phase composition and magnetic properties of Gd-doped La 1− x Gd x Fe 11.5 Si 1.5 alloy have been investigated. • Atomic resolution STEM imaging and EDS elemental analysis have been performed at the phase boundaries in the alloys. • The effect of Gd doping on the microstructure and magnetic properties of La 1− x Gd x Fe 11.5 Si 1.5 alloys was discussed. [ABSTRACT FROM AUTHOR]