The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3（A = alkali metals） has generated considerable research interest, primarily owing to their reduced dimensionality, significant e...The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3（A = alkali metals） has generated considerable research interest, primarily owing to their reduced dimensionality, significant electron correlations,and possible unconventional superconductivity. The upper critical field（Hc2） provides important information on the superconducting pairing. In this paper, we first briefly overview the latest research progress on the Cr-based superconductors.Then, we introduce typical Hc2（T） behaviors of type-II superconductors in relation with the pair-breaking mechanisms.After a description of the measurement method for Hc2, we focus on the analysis of Hc2 data, especially for the temperature and angle dependence, in K2Cr3As3 crystals. The result indicates（i） an absence of Pauli-paramagnetic pair breaking for field perpendicular to the Cr3As3 chains, and（ii） a unique threefold modulation for the in-plane Hc2Φ profile. Finally we conclude with remarks on the possible unconventional superconducting pairing symmetry.展开更多
Cr coatings,as protective coatings of Zr-alloy fuel claddings,inevitably suffer from irradiation damage before they would possibly run into the accident condition.This study evaluates the radiation and oxidation toler...Cr coatings,as protective coatings of Zr-alloy fuel claddings,inevitably suffer from irradiation damage before they would possibly run into the accident condition.This study evaluates the radiation and oxidation tolerance of three Cr-based coatings with different microstructures(Cr,CrAlSi,and CrAlSiN)through He2+ion irradiation and 1200℃ steam oxidation.The Cr and CrAlSi coatings experienced significant structural degradation,characterized by He bubble aggregation and amplified Kirkendall effects at elevated temperatures.In contrast,the irradiated CrAlSiN coating maintained structural integrity without measurable irradiation hardening.Following annealing at 800℃ for 30 min,approximately 40%of injected He atoms were released,indicating a“self-healing”mechanism.The mechanism is attributed to uniformly distributed,low-density channels that act as sinks and release paths for irradiation-induced defects.Density functional theory simulations suggest that N atoms promote significant rearrangement of ions surrounding the free volume,inhibiting the formation of sites capable of trapping He atoms.Moreover,the CrAlSiN coating exhibited superior oxidation resistance compared to the Cr and CrAlSi coatings,even under high-temperature steam conditions.Notably,the irradiated CrAlSiN sample displayed a significantly thinner oxide scale compared to the pristine one(almost half),owing to a more protective oxide scale and rapid outward diffusion of Cr,Al,and Si through nanochannel veins.These findings illuminate the effects of structure and composition on irradiation and oxidation behavior in Cr-based coatings,offering insights for developing new-generation accident-tolerance fuel coatings for Zr-alloy claddings.展开更多
Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band str...Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band structures and spin−orbit coupling properties.Cr-based chalcogenides with narrow or even zero bandgap,covering from semiconductors to metallic materials,have considerable potential for wide-band photodetection and two-dimensional magnetism.Currently,the preparation of 2D CrX_(n)(X=S,Se,Te)nanosheets primarily relies on chemical vapor deposition(CVD)and molecule beam epitaxy(MBE),which enable the production of high-quality large-area materials.This review article focuses on recent progress of 2D Cr-based chalcogenides,including unique crystal structure of the CrX_(n)system,phase-controlled synthesis,and heterojunction construction.Furthermore,a detailed introduction of room-temperature ferromagnetism and electrical/optoelectronic properties of 2D CrXn is presented.Ultimately,this paper summarizes the challenges associated with utilizing 2D Cr-based chalcogenides in preparation strategies,optoelectronics devices,and spintronic devices while providing further insights.展开更多
Muon spin relaxation/rotation(μSR) is a vital technique for probing the superconducting gap structure, pairing symmetry and time reversal symmetry breaking, enabling an understanding of the mechanisms behind the unco...Muon spin relaxation/rotation(μSR) is a vital technique for probing the superconducting gap structure, pairing symmetry and time reversal symmetry breaking, enabling an understanding of the mechanisms behind the unconventional superconductivity of cuprates and Fe-based high-temperature superconductors, which remain a puzzle. Very recently double layered Fe-based superconductors having quasi-2 D crystal structures and Cr-based superconductors with a quasi-1D structure have drawn considerable attention. Here we present a brief review of the characteristics of a few selected Fe-and Cr-based superconducting materials and highlight some of the major outstanding problems, with an emphasis on the superconducting pairing symmetries of these materials. We focus on μSR studies of the newly discovered superconductors ACa_2Fe_4As_4F_2(A = K, Rb, and Cs), ThFeAsN, and A_2Cr_3As_3(A = K, Cs), which were used to determine the superconducting gap structures, the presence of spin fluctuations, and to search for time reversal symmetry breaking in the superconducting states. We also briefly discuss the results of μSR investigations of the superconductivity in hole and electron doped BaFe_2As_2.展开更多
In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a sp...In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a space group of P63/mcm(No.193)and lattice parameters of a=b=8.9845A and c=5.8897A.The structure contains facesharing octahedral CrAs6 chains along the c-axis,which are arranged triangularly in the ab-plane and separated by a significantly large distance of 8.9845A.The magnetic properties,resistivity and specific heat measurements were performed.La3CrAs5 exhibits a metallic state with Fermi liquid behavior at low temperatures and undergoes a ferromagnetic transition at Curie temperature TC^50 K.First-principles theoretical studies were conducted to calculate its band structure and density of states(DOS),which indicated that the non-negligible contribution of La to the DOS near the Fermi level caused La3CrAs5 to be a three-dimensional(3D)metal.The crystal orbital Hamilton population(-COHP)was also calculated to explain the global stability and bonding characteristics in the structure of La3CrAs5.展开更多
CO_(2) can be used as a soft oxidant for oxidative dehydrogenation of light alkanes(CO_(2)-ODH),which is beneficial to realize the reuse of CO_(2) and meet the demand for olefins.The core of this reaction is the catal...CO_(2) can be used as a soft oxidant for oxidative dehydrogenation of light alkanes(CO_(2)-ODH),which is beneficial to realize the reuse of CO_(2) and meet the demand for olefins.The core of this reaction is the catalyst.Cr-based catalysts have attracted much attention for their excellent catalytic performance in CO_(2)-ODH reactions due to their various oxidation states and local electronic structures.In this paper,the synthesis and modification methods of Cr-based catalysts for CO_(2)-ODH are reviewed.The structure-activity relationship and reaction mechanism are also summarized.Moreover,the reasons for the deactivation of Cr-based catalysts are analysed and the main challenges faced by Cr-based catalysts in the CO_(2)-ODH process,as well as the future development trend and prospect,are discussed.展开更多
Efficient electrocatalysis at the cathode is crucial to addressing the limited stability and low rate capability of Li−O_(2)batteries.This study examines the kinetic behavior of Li−O_(2)batteries utilizing layered per...Efficient electrocatalysis at the cathode is crucial to addressing the limited stability and low rate capability of Li−O_(2)batteries.This study examines the kinetic behavior of Li−O_(2)batteries utilizing layered perovskite LaSrCrO_(4)nanowires(NWs)composed of lower oxidation states.Layered perovskite LaSrCrO_(4)NWs exhibited improved rate capability over a wide range of current densities and longer cycle life in Li−O_(2)batteries than V-based layered perovskite(LaSrVO_(4))and simple perovskite(La_(0.8)Sr_(0.2)CrO_(3))NWs.X-ray photoelectron spectroscopy and electrochemical surface area analyses showed that the observed performance variations primarily stemmed from active sites such as oxygen vacancies.In situ Raman analysis showed that these active sites significantly modulate the kinetics of oxygen reduction and evolution,which are related to LiO_(2)intermediate adsorption.Electrochemical impedance spectroscopy showed that the active sites in layered perovskite LaSrCrO_(4)NWs contributed to their high charge transfer capability and reduced polarization.This study presents an appealing method for the precise fabrication and analysis of Cr-based layered perovskites,aimed at achieving highly efficient and stable bifunctional oxygen electrocatalysis.展开更多
Quasi-one-dimensional(Q1D) Cr-based pnictide K_(2)Cr_(3)As_(3)exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity ...Quasi-one-dimensional(Q1D) Cr-based pnictide K_(2)Cr_(3)As_(3)exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis,crystal structure, physical properties, and density functional theory(DFT) calculations of(nearly) fully hydrogenized K_(2)Cr_(3)As_(3)H.It is found that the intercalation of hydrogen in K_(2)Cr_(3)As_(3)leads to absence of metallicity as well as superconductivity. An antiferromagnetic transition nearby room temperature is evidenced from the measurements of magnetic susceptibility and heat capacity.The antiferromagnetic insulating state can be reproduced by the DFT calculations, which show a novel non-collinear co-planar magnetic order. Our result sheds light on the mechanism of unconventional superconductivity in Q1D Cr-based superconductors.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674281 and 11574097)the Fundamental Research Funds for the Central Universities of China
文摘The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3（A = alkali metals） has generated considerable research interest, primarily owing to their reduced dimensionality, significant electron correlations,and possible unconventional superconductivity. The upper critical field（Hc2） provides important information on the superconducting pairing. In this paper, we first briefly overview the latest research progress on the Cr-based superconductors.Then, we introduce typical Hc2（T） behaviors of type-II superconductors in relation with the pair-breaking mechanisms.After a description of the measurement method for Hc2, we focus on the analysis of Hc2 data, especially for the temperature and angle dependence, in K2Cr3As3 crystals. The result indicates（i） an absence of Pauli-paramagnetic pair breaking for field perpendicular to the Cr3As3 chains, and（ii） a unique threefold modulation for the in-plane Hc2Φ profile. Finally we conclude with remarks on the possible unconventional superconducting pairing symmetry.
基金supported by the National Natu-ral Science Foundation of China(No.U2230126)the Natural Science Foundation of Zhejiang Province(No.LZ23E010001)+1 种基金This work was co-funded by the European Union under the Project Robotics and Advanced Industrial Production(Reg.No.CZ.02.01.01/00/22_008/0004590)supported by the Ministry of Education,Youth and Sports of the Czech Repub-lic through the e-INFRA CZ grant number ID:90140.Access to the computational infrastructure of the OP VVV funded Project No.CZ.02.1.01/0.0/0.0/16_019/0000765“Research Center for Informat-ics”and the use of the VESTA software[https://doi.org/10.1107/S0021889808012016]are also acknowledged.The authors thank the staffof HIRFL for the help with the irradiation experiment and the support of the Sharing Service Platform of CAS Large Re-search Infrastructures(2022-HIRFL-ZD-002017)。
文摘Cr coatings,as protective coatings of Zr-alloy fuel claddings,inevitably suffer from irradiation damage before they would possibly run into the accident condition.This study evaluates the radiation and oxidation tolerance of three Cr-based coatings with different microstructures(Cr,CrAlSi,and CrAlSiN)through He2+ion irradiation and 1200℃ steam oxidation.The Cr and CrAlSi coatings experienced significant structural degradation,characterized by He bubble aggregation and amplified Kirkendall effects at elevated temperatures.In contrast,the irradiated CrAlSiN coating maintained structural integrity without measurable irradiation hardening.Following annealing at 800℃ for 30 min,approximately 40%of injected He atoms were released,indicating a“self-healing”mechanism.The mechanism is attributed to uniformly distributed,low-density channels that act as sinks and release paths for irradiation-induced defects.Density functional theory simulations suggest that N atoms promote significant rearrangement of ions surrounding the free volume,inhibiting the formation of sites capable of trapping He atoms.Moreover,the CrAlSiN coating exhibited superior oxidation resistance compared to the Cr and CrAlSi coatings,even under high-temperature steam conditions.Notably,the irradiated CrAlSiN sample displayed a significantly thinner oxide scale compared to the pristine one(almost half),owing to a more protective oxide scale and rapid outward diffusion of Cr,Al,and Si through nanochannel veins.These findings illuminate the effects of structure and composition on irradiation and oxidation behavior in Cr-based coatings,offering insights for developing new-generation accident-tolerance fuel coatings for Zr-alloy claddings.
基金supported by the Science and Technology Innovation Program of Hunan Province(“HuXiang Young Talents”,Grant No.2021RC3021),the Natural Science Foundation of Hunan Province,China(Grant No.2021JJ40780)the National Natural Science Foundation of China(Grant No.51902346)supported by the Open Project Program of Shanxi Key Laboratory of Advanced Semiconductor Optoelectronic Devices and Integrated Systems(Grant No.2023SZKF14).
文摘Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band structures and spin−orbit coupling properties.Cr-based chalcogenides with narrow or even zero bandgap,covering from semiconductors to metallic materials,have considerable potential for wide-band photodetection and two-dimensional magnetism.Currently,the preparation of 2D CrX_(n)(X=S,Se,Te)nanosheets primarily relies on chemical vapor deposition(CVD)and molecule beam epitaxy(MBE),which enable the production of high-quality large-area materials.This review article focuses on recent progress of 2D Cr-based chalcogenides,including unique crystal structure of the CrX_(n)system,phase-controlled synthesis,and heterojunction construction.Furthermore,a detailed introduction of room-temperature ferromagnetism and electrical/optoelectronic properties of 2D CrXn is presented.Ultimately,this paper summarizes the challenges associated with utilizing 2D Cr-based chalcogenides in preparation strategies,optoelectronics devices,and spintronic devices while providing further insights.
基金supported by the National Natural Science Foundation of China(Grant No.11874320)the National Key Research and Development Program of China(Grant No.2017YFA0303100)+2 种基金the Royal Society of London for the UK-China Newton funding and CMPC-STFC(Grant No.CMPC-09108)the DST India,for Inspire Faculty Research(Grant No.DST/INSPIRE/04/2015/000169)and UK-India Newton funding
文摘Muon spin relaxation/rotation(μSR) is a vital technique for probing the superconducting gap structure, pairing symmetry and time reversal symmetry breaking, enabling an understanding of the mechanisms behind the unconventional superconductivity of cuprates and Fe-based high-temperature superconductors, which remain a puzzle. Very recently double layered Fe-based superconductors having quasi-2 D crystal structures and Cr-based superconductors with a quasi-1D structure have drawn considerable attention. Here we present a brief review of the characteristics of a few selected Fe-and Cr-based superconducting materials and highlight some of the major outstanding problems, with an emphasis on the superconducting pairing symmetries of these materials. We focus on μSR studies of the newly discovered superconductors ACa_2Fe_4As_4F_2(A = K, Rb, and Cs), ThFeAsN, and A_2Cr_3As_3(A = K, Cs), which were used to determine the superconducting gap structures, the presence of spin fluctuations, and to search for time reversal symmetry breaking in the superconducting states. We also briefly discuss the results of μSR investigations of the superconductivity in hole and electron doped BaFe_2As_2.
基金supported by the National Key R&D Program of China and the National Natural Science Foundation of China(2018YFA0305700,11974410,2017YFA0302900,2015CB921300,11534016 and 11974062)。
文摘In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a space group of P63/mcm(No.193)and lattice parameters of a=b=8.9845A and c=5.8897A.The structure contains facesharing octahedral CrAs6 chains along the c-axis,which are arranged triangularly in the ab-plane and separated by a significantly large distance of 8.9845A.The magnetic properties,resistivity and specific heat measurements were performed.La3CrAs5 exhibits a metallic state with Fermi liquid behavior at low temperatures and undergoes a ferromagnetic transition at Curie temperature TC^50 K.First-principles theoretical studies were conducted to calculate its band structure and density of states(DOS),which indicated that the non-negligible contribution of La to the DOS near the Fermi level caused La3CrAs5 to be a three-dimensional(3D)metal.The crystal orbital Hamilton population(-COHP)was also calculated to explain the global stability and bonding characteristics in the structure of La3CrAs5.
文摘CO_(2) can be used as a soft oxidant for oxidative dehydrogenation of light alkanes(CO_(2)-ODH),which is beneficial to realize the reuse of CO_(2) and meet the demand for olefins.The core of this reaction is the catalyst.Cr-based catalysts have attracted much attention for their excellent catalytic performance in CO_(2)-ODH reactions due to their various oxidation states and local electronic structures.In this paper,the synthesis and modification methods of Cr-based catalysts for CO_(2)-ODH are reviewed.The structure-activity relationship and reaction mechanism are also summarized.Moreover,the reasons for the deactivation of Cr-based catalysts are analysed and the main challenges faced by Cr-based catalysts in the CO_(2)-ODH process,as well as the future development trend and prospect,are discussed.
基金National Research Foundation of Korea(NRF)Ministry of Education,Grant/Award Number:2020R1A6A1A03045059+1 种基金Creative Materials Discovery Program,Grant/Award Number:2018M3D1A1058744Korea University Grant。
文摘Efficient electrocatalysis at the cathode is crucial to addressing the limited stability and low rate capability of Li−O_(2)batteries.This study examines the kinetic behavior of Li−O_(2)batteries utilizing layered perovskite LaSrCrO_(4)nanowires(NWs)composed of lower oxidation states.Layered perovskite LaSrCrO_(4)NWs exhibited improved rate capability over a wide range of current densities and longer cycle life in Li−O_(2)batteries than V-based layered perovskite(LaSrVO_(4))and simple perovskite(La_(0.8)Sr_(0.2)CrO_(3))NWs.X-ray photoelectron spectroscopy and electrochemical surface area analyses showed that the observed performance variations primarily stemmed from active sites such as oxygen vacancies.In situ Raman analysis showed that these active sites significantly modulate the kinetics of oxygen reduction and evolution,which are related to LiO_(2)intermediate adsorption.Electrochemical impedance spectroscopy showed that the active sites in layered perovskite LaSrCrO_(4)NWs contributed to their high charge transfer capability and reduced polarization.This study presents an appealing method for the precise fabrication and analysis of Cr-based layered perovskites,aimed at achieving highly efficient and stable bifunctional oxygen electrocatalysis.
基金supported by the Key Research and Development Program of Zhejiang Province,China(Grant No.2021C01002)the National Natural Science Foundation of China(Grant Nos.12050003,and 11674281)。
文摘Quasi-one-dimensional(Q1D) Cr-based pnictide K_(2)Cr_(3)As_(3)exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis,crystal structure, physical properties, and density functional theory(DFT) calculations of(nearly) fully hydrogenized K_(2)Cr_(3)As_(3)H.It is found that the intercalation of hydrogen in K_(2)Cr_(3)As_(3)leads to absence of metallicity as well as superconductivity. An antiferromagnetic transition nearby room temperature is evidenced from the measurements of magnetic susceptibility and heat capacity.The antiferromagnetic insulating state can be reproduced by the DFT calculations, which show a novel non-collinear co-planar magnetic order. Our result sheds light on the mechanism of unconventional superconductivity in Q1D Cr-based superconductors.
