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Quick preparation and thermal transport properties of nanostructured β-FeSi_2 bulk material

Chinese Physics B 2009年第1期18卷 287-292页

作者：李涵唐新峰曹卫强张清杰 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning （MS） and subsequent spark plasma sintering （SPS）. It investigates the influence of linear speed of the rolling copper wheel, injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively, and discusses the effects of the microstructure on thermal transport properties. There are two crystalline phases （α-Fe2Si5 and ε-FeSi） in the rapidly solidified ribbons; the crystal grains become smaller when the cooling rate increases （the 20 nm minimum crystal of ε-FeSi is obtained）. Having been sintered for 1 min above 1123K and annealed for 5min at 923K, the single-phase nanostructured β- FeSi2 bulk materials with 200-500 nm grain size and 98% relative density are obtained. The microstructure of β-FeSi2 has great effect on thermal transport properties. With decreasing sintering temperature, the grain size decreases, the thermal conductivity of β-FeSi2 is reduced remarkably. The thermal conductivity of β-FeSi2 decreases notably （reduced 72% at room temperature） in comparison with the β-FeSi2 prepared by traditional casting method.

关键词： thermoelectric materials nanostructure thermal conductivity

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Realization of non-equilibrium process for high thermoelectric performance Sb-doped Ge Te

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Science Bulletin 2018年第11期63卷 717-725页

作者： Evariste Nshimyimana Xianli Su Hongyao Xie Wei Liu Rigui Deng Tingting Luo Yonggao Yan Xinfeng Tang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

Pristine GeTe shows inferior thermoelectric performance around unit due to the large carrier concentration induced by the presence of intrinsic high concentration of Ge vacancy. In this study, we report a thermoelectric figure of merit ZT of 1.56 at 700 K, realized in Sb-doped GeTe based thermoelectric(TE)materials via combined effect of suppression of intrinsic Ge vacancy and Sb doping. The nonequilibrium nature during melt spinning process plays very important role. For one thing, it promotes the homogeneity in Ge_(1-x)Sb_xTe samples and refines the grain size of the product. Moreover the persistent Ge precipitated as impurity phase in the traditional synthesis process is found to be dissolved back into the GeTe sublattice, accompanying with a drastic suppression of Ge vacancies concentration which in combination with Sb electron doping significantly reduced the inherent carrier concentration in *** carrier concentration, approaching the optimum carrier concentration ～3.74 × 10^(-20) cm^(-3) and a high power factor of 4.01 × 10^(-3) W m^(-1)K^(-2) at 750 K are achieved for Ge_(0.98)Sb_(0.02) Te sample. In addition,the enhanced grain boundary phonon scattering by refining the grain size through melt spinning(MS)process, coupled with the intensified alloying phonon scattering via Sb doping leads to low thermal conductivity of 1.53 W m^(-1) K^(-1) at 700 K for Ge_(0.94) Sb_(0.06) Te sample. All those contribute to a high ZT value,representing over 50% improvement in the ZT value compared to the Sb free samples, which provides an alternative way for ultrafast synthesis of high performance GeTe based thermoelectric material.

关键词： GeTe Sb doping MS-SPS process Thermoelectric properties

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Phase transition and high temperature thermoelectric properties of copper selenide Cu_(2-x) Se (0 ≤ x ≤ 0.25)

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Chinese Physics B 2011年第8期20卷 340-347页

作者：肖星星谢文杰唐新峰张清杰 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

With good electrical properties and an inherently complex crystal structure, Cu2-xSe is a potential ＂phonon glass electron crystal＂ thermoelectric material that has previously not attracted much interest. In this study, Cu2-xSe （0 ≤ x ≤0.25） compounds were synthesized by a melting-quenching method, and then sintered by spark plasma sintering to obtain bulk material. The effect of Cu content on the phase transition and thermoelectric properties of Cu2-xSe were investigated in the temperature range of 300 K-750 K. The results of X-ray diffraction at room temperature show that Cu2-xSe compounds possess a cubic structure with a space group of Fm3m （#225） when 0.15 〈 x ≤ 0.25, whereas they adopt a composite of monoclinic and cubic phases when 0 ≤x ≤ 0.15. The thermoelectric property measurements show that with increasing Cu content, the electrical conductivity decreases, the Seebeck coefficient increases and the thermal conductivity decreases. Due to the relatively good power factor and low thermal conductivity, the nearly stoichiometric Cu2Se compound achieves the highest ZT of 0.38 at 750 K. It is expected that the thermoelectric performance can be further optimized by doping appropriate elements and/or via a nanostructuring approach.

关键词： copper selenide phase transition thermoelectric properties

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Charge and spin instabilities in superconducting La3Ni2O7

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Physical Review B 2025年第1期111卷 014515-014515页

作者： Xuejiao Chen Peiheng Jiang Jie Li Zhicheng Zhong Yi Lu National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Nanjing 210093 China Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo 315201 China School of Photoelectric Engineering Changzhou Institute of Technology Changzhou Jiangsu 213002 China School of Physics MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter Xi'an Jiaotong University Xi'an 710049 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

Motivated by the recent discovery of superconductivity in La3Ni2O7 under high pressure, we explore its potential charge and spin instabilities through combined model analysis and first-principles calculations. Taking into account the small charge-transfer nature of high valence nickel, a fully correlated two-cluster model identifies a lattice-coupled charge instability characterized by substantial short-range fluctuations of oxygen holes. This periodicity-two instability is corroborated by density functional theory plus U calculations that also reveal a strong tendency towards concurrent antiferromagnetic ordering. The charge, spin, and associated lattice instabilities are significantly suppressed with increasing external pressure, contributing to the emergence of superconductivity in pressurized La3Ni2O7. Carrier doping and chemical substitution at the La site is found to effectively suppress these instabilities, suggesting a viable strategy to stabilize a superconducting phase under ambient pressure.

关键词： Charge transfer

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Organic–inorganic S-scheme heterojunction photocatalysts: Design, synthesis, applications, and challenges

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eScience 2025年第3期5卷

作者： Cheng, Jingzhao Cheng, Bei Xu, Jingsan Yu, Jiaguo Cao, Shaowen State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China Hubei Technology Innovation Center for Advanced Composites Wuhan University of Technology Wuhan 430070 China School of Chemistry and Physics Queensland University of Technology Brisbane QLD Australia Laboratory of Solar Fuel Faculty of Materials Science and Chemistry China University of Geosciences Wuhan 430078 China

Since the concept was introduced in 2019, step-scheme (S-scheme) heterojunctions have emerged as an important subclass of heterojunction technology and attracted much attention for solar energy conversion. S-scheme heterojunctions are capable of maximizing redox ability through conferring enhanced photocatalytic performance by addressing the problem of rapid electron–hole recombination. In particular, the organic–inorganic S-scheme heterojunction (OI-SHJ) can integrate atomic long-range ordered inorganic semiconductors with tailored organic materials using diverse organic molecular building blocks and integration methods, offering brilliant prospects for innovation. Here, we review the state-of-the-art progress in OI-SHJ photocatalysts by introducing their charge transfer mechanism, design criteria, preparation approaches, and applications. We also highlight the synergistic role of organic and inorganic materials in S-scheme heterojunctions and what is understood so far about their structure–activity relationship. We conclude by summarizing the existing challenges and emphasizing the current outlook for the future development of OI-SHJ photocatalysts. © 2024 The Authors

关键词： Energy conversion Organic–inorganic Photocatalysis S-scheme

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Simultaneous Enhancement of Electron and Phonon Transport Properties via Magnetism Phase Transition in FexCo2-xTiGe Heusler Alloy

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Small 2025年 e2500154页

作者： Li, Yongqiang Wang, Hanwen Cui, Wenjun Lin, Weixiao Sun, Yue Zhao, Wen Sang, Xiahan State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan430070 China Wuhan University of Technology Shenzhen Institute Shenzhen518000 China Nanostructure Research Center Wuhan University of Technology Wuhan430070 China Shandong Qingdao266580 China

Magnetism offers an additional degree of freedom to control the electron and phonon transport properties of thermoelectric materials through various thermoelectromagnetic effects. To better understand the interplay among spin, carriers, and phonons, it is important to design material systems with intrinsic magnetic and thermoelectric properties. Here, it is demonstrated that Fe doping of the full Heusler alloy Co2TiGe simultaneously enhances its magnetic and thermoelectric performance. Aberration-corrected scanning transmission electron microscopy (STEM) reveals that Fe atoms preferentially substitute for Co atoms within the Co2TiGe lattice, leading to increased saturation magnetization and a higher Curie temperature. This Fe substitution reduces the carrier concentration, enhancing the Seebeck coefficient and power factor, while also increasing magnetic scattering due to spin fluctuations during the ferromagnetic-paramagnetic phase transition. Furthermore, the thermal conductivity is significantly reduced by enhanced phonon scattering from secondary phases and point defects. Consequently, a maximum ZT value of 0.066 is achieved at 600 K for Fe0.4Co1.6TiGe, representing a 663% increase compared to the undoped Co2TiGe. © 2025 Wiley-VCH GmbH.

关键词： Saturation magnetization

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Argon-assisted electrical explosion of graphite powder in a constraint tube: Experimental and MD insights into the exfoliation mechanism

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Ceramics International 2025年

作者： Zhu, Wenli Zhu, Liang Department of Civil and Environmental Engineering University of California Los Angeles United States School of Materials Science and Engineering State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals Lanzhou University of Technology Lanzhou730050 China

We report a top-down electrical explosion approach in a constraint tube under an argon atmosphere for high-yield production of few-to multi-layer graphene. By coupling high-voltage discharges with inert gas support, this technique imparts intense shock loading that surmounts the interlayer van der Waals forces in graphite. Systematic experimental analyses (FE-SEM, TEM/HRTEM, AFM, Raman) confirm efficient exfoliation into largely few-layer graphene with minimal defects and residual graphite. To elucidate the atomistic mechanisms, large-scale molecular dynamics (MD) simulations replicate key stages of the process—annealing, shock-induced delamination, and cooling—revealing how shock loading and argon interactions drive interlayer expansion, bending, and partial delamination. Notably, argon significantly mitigates re-agglomeration during the cooling stage, preserving dispersed graphene flakes. This synergy between experiment and simulation establishes electrical explosion in an argon-rich environment as a scalable method potentially suitable for commercial graphene production. Moreover, it highlights the crucial role of controlled shock conditions and argon gas interactions in enabling robust, few-layer exfoliation, paving the way for further optimization and industrial implementation. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Van der Waals forces

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Large Tunneling Magnetoresistance in Nonvolatile 2D Hybrid Spin Filters

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Physical Review Letters 2025年第7期134卷 077001-077001页

作者： Xiaoyu Wang Lihao Zhang Miao He Qi Li Wenqin Song Kunlin Yang Shuxi Wang Takashi Taniguchi Kenji Watanabe MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter Shaanxi Province Key Laboratory of Advanced Materials and Mesoscopic Physics School of Physics Xi’an Jiaotong University Xi’an 710049 China Anhui Key Laboratory of Low-Energy Quantum Materials and Devices High Magnetic Field Laboratory Hefei Institutes of Physical Science Chinese Academy of Sciences Hefei 230031 China Science Island Branch of Graduate School University of Science and Technology of China Hefei 230026 China Key Laboratory of Flexible Electronics and Institute of Advanced Materials Nanjing Tech University Nanjing 211816 China State Key Laboratory of Surface Physics and Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 China Research Center for Materials Nanoarchitectonics National Institute for Materials Science Tsukuba 305-0044 Japan Research Center for Electronic and Optical Materials National Institute for Materials Science Tsukuba 305-0044 Japan

Ferromagnetic semiconductors offer an efficient way to achieve high spin polarization via spin filtering effect. Large tunneling magnetoresistance (TMR) can then be realized when multiple spin filters are put in series, as recently demonstrated in van der Waals 2D A-type antiferromagnets such as CrI3 and CrSBr. However, the interlayer antiferromagnetic ground state of these magnets inherently results in a high resistance state at zero field, and this volatile behavior limits potential applications. Here we fabricate hybrid spin filters using 2D ferromagnetic metal Fe3GeTe2 and semiconductor CrBr3, which are nonvolatile as two magnets are magnetically decoupled. We achieve large TMR of around 100%, with its temperature dependence well fitted by the extended Jullière model. Additionally, the devices allow spin injection tuned through bias voltage, and TMR polarity reversals are observed. Our work opens a new route to develop 2D magnetic semiconductor based spintronics.

关键词： Van der Waals forces

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Crystal Structures and Thermoelectric Properties of Sm-Filled Skutterudite Compounds Sm_yFe_xCo_(4-x)Sb_(12)

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Journal of Rare Earths 2007年第6期25卷 739-743页

作者：刘桃香唐新峰谢文杰鄢永高张清杰 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 samples possessed filled skutterudite structures. The thermal parameter （B） of Sm is larger than that of Sb, Fe, and Co, indicating that Sm ＂rattled＂ in Sb-icosahedron voids. The effects of filling atom Sm on thermoelectric properties of these compounds were investigated. With the increase of Sm filling fraction （y）, electrical conductivity decreased, Seebeck coefficient increased and had a maximum value when y was 0.38; thermal conductivity reduced and had a minimum value when y was 0. 32. At 750 K, the highest figure of merit of 0.68 was obtained for Sm0.32Fe1.47Co2.53Sb12.

关键词： skutterudite compound thermoelectric properties Sm filling rare earths

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Rare earth metal oxides as BH_4^--tolerance cathode electrocatalysts for direct borohydride fuel cells

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Journal of Rare Earths 2012年第5期30卷 437-441页

作者：倪学敏王雅东郭峰姚佩潘牧 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

Rare earth metal oxides（REMO） as cathode electrocatalysts in direct borohydride fuel cell（DBFC） were *** REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline *** simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm *** DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better *** maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.

关键词： direct borohydride fuel cell oxygen electro-reduction rare earth oxide membraneless DBFC

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