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Polarization switching in ferroelectric HfO2 from first-principles lattice mode analysis

Physical Review B 2025年第13期111卷 134106-134106页

作者： Yubo Qi Sobhit Singh Karin M. Rabe Department of Physics University of Alabama at Birmingham Birmingham Alabama 35294 USA Department of Mechanical Engineering University of Rochester Rochester New York 14627 USA Materials Science Program University of Rochester Rochester New York 14627 USA Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA

In this paper, we introduce a first-principles-based lattice mode analysis method to investigate the competition between different polarization switching paths in HfO2. Because the stability of the polar orthorhombic Pca21 phase of HfO2 arises from a trilinear coupling, polarization switching requires the flipping of not only the polar Γ15Z mode, but also at least one zone-boundary antipolar mode. This means that each polarization state has multiple variants, leading to multiple possible switching paths connecting up- and down-polarized states, which can be systemically enumerated within this framework for efficient identification of the optimal switching path. Our lattice mode analysis also explains why the activation energy of propagation of the most widely studied domain-wall structure in HfO2, which requires the reversal of the X2− mode, is much larger than that of propagation of domain-wall structures with a uniform sign for the X2− mode. This approach deepens our understanding of distinctive properties of ferroelectric HfO2 related to polarization switching and domain-wall motion, including sluggish domain-wall motion, robust ferroelectricity in thin films, and the observation that the antipolar Pbca phase can hardly be transformed to the ferroelectric Pca21 phase by an electric field. Our mode analysis method can be more generally applied to any improper or hybrid improper ferroelectric, in which polarization switching requires changes of nonpolar distortions, for systematic and efficient prediction of optimal switching paths and estimation of coercive fields.

关键词： Ferroelectricity

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Bandgap of Epitaxial Single-Crystal BiFe1−xMnxO3 Films Grown Directly on SrTiO3/Si(001)

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materials 2025年第9期18卷 2022-2022页

作者： Cantrell, Samuel R. Miracle, John T. Cottier, Ryan J. Lindsey, Skyler Theodoropoulou, Nikoleta Materials Science Engineering and Commercialization Program Texas State University San MarcosTX78666 United States Department of Physics Texas State University San MarcosTX78666 United States

We report the growth and optical characterization of single-crystal BiFe1−xMnxO3 thin films directly on SrTiO3/Si(001) substrates using molecular beam epitaxy. X-ray diffraction confirmed epitaxial growth, film crystallinity, and sharp interface quality. Scanning electron microscopy and energy dispersive X-ray spectroscopy verified uniform film morphology and successful Mn incorporation. Spectroscopic ellipsometry revealed a systematic bandgap reduction with increasing Mn concentration, from 2.7 eV in BiFeO3 to 2.58 eV in BiFe0.74Mn0.26O3, consistent with previous reports on Mn-doped BiFeO3. These findings highlight the potential of BiFe1₋xMnxO3 films for bandgap engineering, advancing their integration into silicon-compatible multifunctional optoelectronic and photovoltaic applications. © 2025 by the authors.

关键词： Molecular beam epitaxy

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Searching for quantum nonthermodynamic phenomena

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Physical Review E 2025年第5期111卷 054108-054108页

作者： Yu Qiao Program of Materials Science and Engineering University of California–San Diego La Jolla California 92093 USA and Department of Structural Engineering University of California–San Diego La Jolla California 92093-0085 USA

Recent research on the fundamentals of statistical mechanics has led to an interesting discovery. With locally nonchaotic barriers, as Boltzmann's H theorem is inapplicable, there exist nontrivial nonthermodynamic systems that can produce useful work by absorbing heat from a single thermal reservoir without any other effect, thereby breaking the boundaries of the second law of thermodynamics. The previous analyses used classical mechanical models. In the current investigation, the study is extended to quantum mechanics. First, we reiterate that the Fermi-Dirac distribution and the Bose-Einstein distribution are compatible with the generalized Maxwell's relations, which demonstrates the general robustness of the framework of quantum statistical mechanics. Next, we analyze a set of simple-step scattering problems. When the system is in contact with a thermal reservoir, a bound state inherently follows the second law of thermodynamics, while a scattering state may not. The root cause is associated with the nonlocal nature of the wave function. It implies that the nonthermodynamic phenomena favor unquantized energy and localized wave packets, exhibiting a tendency to occur in “semiclassical” setups.

关键词： Statistical mechanics

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Theoretical insights into metal-doped nanostructured hematite catalyst supported by graphene underlayer for photoelectrochemical water splitting applications

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Discover Catalysis 2025年第1期2卷 1-27页

作者： Bhattacharya, Labanya Caspary Toroker, Maytal Department of Materials Science and Engineering Technion-Israel Institute of Technology Haifa Israel The Nancy and Stephen Grand Technion Energy Program Technion-Israel Institute of Technology Haifa Israel Resnick Sustainability Center for Catalysis Technion-Israel Institute of Technology Haifa Israel

Catalysis is pivotal in the production of green hydrogen through water splitting to meet the goal of carbon neutrality. Hematite (Fe2O3) is an excellent catalyst and benchmarked photoanode materials in photoelectrochemical water splitting. Among the metal dopants, aluminum (Al) substitution in hematite is found intrinsically. In this study, we investigate Al doped nanostructured hematite as a photoanode material and a catalyst in water oxidation mechanism using density functional theory+ U methodology. We have found that Al doping in hematite monolayer leads to unfavorable increase in theoretical overpotential value by 0.19 V. To improve the efficiency of oxygen evolution reaction, we consider heterostructuring of Al doped nanostructured hematite with pristine graphene and nitrogen (N) doped graphene as an underlayer material. Nitrogen doped graphene underlayer leads to the lowest overpotential value of 0.54 V compared to Al doped hematite catalyst (0.96 V) and graphene-Al doped hematite catalyst (0.63 V). The work function is notably reduced after nitrogen doping by 1.41 eV and 1.12 eV as compared to graphene-Al doped hematite and Al doped hematite, respectively. Charge density difference and Bader charge analysis confirm that nitrogen doped graphene underlayer induces delocalized charge density and lowers the activity of the surface states in the *O intermediate. Nitrogen doped graphene-Al doped hematite heterostructure has nearly zero band gap and has the highest cumulative probability of charge transport at photoanode’s surface. Our theoretical study provides mechanistic insights into improving the catalytic efficiency of Al doped nanostructured hematite by heterostructuring with pristine and N doped graphene.

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Increased corrosion resistance of steel substrates coated with epoxy resin/ZnO/Fe 2 O 3 obtained from electric arc furnace dust recovery

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Journal of materials Research and Technology 2025年 36卷 9462-9472页

作者： Mário Andrean Macedo Castro Tanara Caroline Nunes Nicácio Antonio Carlos do Nascimento Santos José Eudes Lima Santos Luis David Loor-Urgilés Antonio Eduardo Martinelli Fabiana Villela da Motta Mauricio Bomio LSQM–Laboratory of Chemical Synthesis of Materials Department of Materials Engineering Federal University of Rio Grande do Norte – UFRN P.O. Box 1524 Natal RN Brazil Institute of Chemistry Federal University of Rio Grande do Norte 59078-970 Natal RN Brazil Postgraduate Program in Materials Science and Engineering Federal University of Rio Grande do Norte 59078-900 Natal RN Brazil

The sustainable management of metal-rich industrial wastes, such as electric arc furnace dust (EAFD), remains a critical challenge for the steel industry. Although previous studies have investigated metal recovery routes and their application in functional materials, few have explored the reuse of these wastes as active components in anticorrosive coatings. This work proposes an innovative approach for valorizing EAFD, recovering iron (Fe 2 O 3 ) and zinc (ZnO) oxides through acid leaching, basic precipitation, and heat treatment. After recovery, mixed ZnO/Fe 2 O 3 oxides were prepared in different proportions and incorporated as nanofillers in an epoxy matrix, creating a hybrid coating aimed at protecting carbon steel against corrosion. The obtained materials were characterized by XRF, XRD, FTIR, SEM, and BET analysis, while the mechanical and anticorrosive properties were evaluated by Vickers hardness tests, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy. After 240 h of immersion in saline solution and 360 h of Salt-spray test, the coating with the highest Fe 2 O 3 content demonstrated superior performance, reducing the corrosion rate by up to 100 times and increasing the load transfer resistance by up to 80 times. The contribution of this study lies in both the proposal of a new cycle for reusing steel waste and in demonstrating a viable route for developing high-performance anticorrosive coatings with potential for industrial application in sectors such as oil and gas. The combination of waste recovery and functional improvement of the material positions this study as a technologically and environmentally relevant solution.

关键词： EAFD ZnO Fe 2 O 3 Epoxy resin Anti-corrosive coatings

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Reactive Synthesis and Ultrafast Sintering of Refractory Compositionally Complex Alloy-Carbide Composites

SSRN

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SSRN 2025年

作者： Shivakumar, Sashank Luo, Jian Aiiso Yufeng Li Family Department of Chemical and Nano Engineering University of California La Jolla San DiegoCA92093 United States Program in Materials Science and Engineering University of California La Jolla San DiegoCA92093 United States

Refractory compositionally complex alloy (RCCA) NbMoTaW with a well-dispersed compositionally complex carbide (CCC) reinforcing secondary phase is made through high-energy ball milling (HEBM) and ultrafast high-temperature sintering (UHS). Stearic acid is used as a process control agent (PCA) for HEBM and a carbon source to form a controllable fraction (~2-20 vol%) of CCC in-situ via reactive synthesis. Ultrahigh heating rates of ~100 °C/s enable sintering of dense (~93-97 % relative densities) bulk compacts of RCCA-CCA composites at ~1850 °C in ~70 seconds. With the addition of 0.1-0.75 wt% PCA, ultrafast sintering enables the formation of a favorable P m1 subcarbide CCC phase, (Nb0.37Mo0.11Ta0.39W0.13)2C. A thermodynamic model is developed to explain the observed Nb and Ta enrichments in (Nb0.37Mo0.11Ta0.39W0.13)2C. An additional rock-salt monocarbide CCC phase forms with more carbon source addition (1 wt% PCA). The well-dispersed and fine-grained CCC precipitates result in grain size refinement and a corresponding increase in hardness. © 2025, The Authors. All rights reserved.

关键词： Grain refinement

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Long-range order of polygonal grain boundaries

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Physical Review B 2025年第4期111卷 045103-045103页

作者： N. Sarkar P. R. Bandaru R. C. Dynes Department of Mechanical Engineering University of California San Diego La Jolla California 92093-0411 USA Program in Materials Science University of California San Diego La Jolla California 92093-0411 USA Department of Physics University of California San Diego La Jolla California 92093-0411 USA

Atomic-scale spatial resolution was achieved in the mapping and spectroscopy of polygonal grain boundaries (GBs) on atomically flat highly oriented pyrolytic graphite using scanning tunneling microscopy (STM). These GBs are long-range ordered one-dimensional periodic structures comprising pentagon-heptagon pairs. A comprehensive study combining local electronic, valleytronic, mechanical, and topological properties is conducted on this GB which reveals the interplay between these properties. On the atoms and bonds of individual GB polygons, spatially localized conductance states were probed, in addition to edge states. The spatial extent of these states was observed on GB by bias-dependent imaging. The electron scattering angle at the GB edges was also modulated with a sample bias which exhibited valley flipping and unique quantum interference effects such as backscattering and intervalley scattering. In situ strain-induced mechanical and electronic modifications were observed through surface deformation caused by the STM tip, revealing flattened electronic energy band dispersion and shifts in carrier doping.

关键词： Grain boundaries

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Large negative magnetoresistance in the off-stoichiometric topological semimetal PrSbxTe2−x

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Physical Review B 2025年第2期111卷 024421-024421页

作者： Gokul Acharya Krishna Pandey M. M. Sharma Jian Wang Santosh Karki Chhetri Md Rafique Un Nabi Dinesh Upreti Rabindra Basnet Josh Sakon Department of Physics University of Arkansas Fayetteville Arkansas 72701 USA Materials Science and Engineering Program Institute for Nanoscience and Engineering University of Arkansas Fayetteville Arkansas 72701 USA Department of Chemistry and Biochemistry Wichita State University Wichita Kansas 67260 USA Department of Chemistry & Physics University of Arkansas at Pine Bluff Pine Bluff Arkansas 71603 USA Department of Chemistry and Biochemistry University of Arkansas Fayetteville Arkansas 72701 USA

Magnetic topological materials LnSbTe (Ln = lanthanide) have attracted intensive attention because of the presence of interplay between magnetism, topological, and electron correlations depending on the choices of magnetic Ln elements. Varying Sb and Te composition is an efficient approach to control structural, magnetic, and electronic properties. Here, we report on the composition-dependent properties in PrSbxTe2−x. We identified the tetragonal-to-orthorhombic structure transitions in this material system and very large negative magnetoresistance in the x=0.3 composition, which might be ascribed to the coupling between magnetism and transport. Such unusual magnetotransport enables PrSbxTe2−x topological materials as a promising platform for device applications.

关键词： Magnetoresistance

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Efficient synthesis method of CsPbBr3/Al2O3 composite powders for scalable production: Augmented green emission and thermal stability

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Journal of Industrial and engineering Chemistry 2025年

作者： Kim, Seok-Hun Shin, Weon Ho Oh, Jong-Min Kim, Sang-Wook Kim, Sunghoon Center for Brain Busan 21 Plus Program Dong-Eui University Busan47340 Korea Republic of Department of Electronic Materials Engineering Kwangwoon University Seoul01897 Korea Republic of Department of Molecular Science and Technology Ajou University Suwon16499 Korea Republic of

Metal halide perovskites (MHPs) have gained significant attention for their exceptional optoelectronic properties, particularly in displays. However, their practical utility is severely limited by their intrinsic instability, including poor thermal stability, photostability, and susceptibility to moisture-induced degradation. This study introduces scalable synthesis of CsPbBr3/Al2O3 green-emitting phosphors, using submicron Al2O3 as a support, comparing mechanochemical reaction (MRM) and dissolution-evaporation (DEM) methods. DEM is the optimal route, enabling the formation of monoclinic CsPbBr3/Al2O3 with high photoluminescence quantum yield (PLQY) and enhanced stability. The influence of the CsPbBr3 to Al2O3 mass ratio on PLQY was quantitatively analyzed using the Halder-Wagner method, which indirectly calculated crystallite size and its correlation with PLQY. The composite demonstrated exceptional thermal stability, maintaining over 90 % of its initial PL intensity after 200 °C exposure for 15 days and showed excellent photostability, maintaining nearly its initial luminous efficiency under the currents of 20 mA and 70 mA for 10000-seconds. When integrated as a green phosphor in a white LED package with K2SiF6:Mn+4 as a red phosphor, it achieved a luminous efficiency of 25 lm W−1 and a color gamut of 112.4 % NTSC. These results highlight the potential of CsPbBr3/Al2O3 composites for cost-effective, stable, and high-performance optoelectronic applications. © 2025 The Korean Society of Industrial and engineering Chemistry

关键词： Perovskite

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Textured BaTiO3 nanorod arrays synthesized via hydrothermal method: Enhanced degradation of Rhodamine B with piezocatalysis

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Ceramics International 2025年

作者： Chiu, Yen-Lun Chang, Kao-Shuo Program on Key Materials Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University No.1 University Road Tainan City70101 Taiwan Department of Materials Science & Engineering National Cheng Kung University No.1 University Road Tainan City70101 Taiwan

This paper presents a hydrothermal method for fabricating textured BaTiO3 (BTO) nanorod arrays with high crystallinity on fluorine-doped tin oxide (FTO) substrates by applying a polarization treatment to the samples to explore the feasibility of enhancing their piezoelectric properties. The preparation of highly textured BTO nanorod arrays using a two-step hydrothermal process was investigated in detail, including the spin-coating process for depositing the TiO2 seed layer, the influence of solution acidity on the hydrothermal synthesis of TiO2 nanorod arrays, and the formation mechanism of textured BTO nanostructures. The piezoelectric constants (d33) of the samples were determined using piezoresponse force microscopy. S-BTO(P), which has high crystallinity and preferential orientation, achieves a d33 as high as 85.4 p.m./V after poling, which is 3.2 times higher than that without textured structures and poling. Our findings revealed that chemically controlling and inducing a preferential orientation in the crystal structure of piezoelectric materials with a seed layer and specific hydrothermal conditions can significantly enhance their piezoelectric properties after poling, making them excellent candidates for piezoelectric devices. Especially, this study confirms that the piezoelectric-enhanced charge separation in poled BTO nanorod arrays enables efficient generation of reactive species under ultrasonication, leading to effective degradation of RhB. The strong piezocatalytic performance highlights the material's potential for practical applications in environmental pollutant removal. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Piezoelectricity

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