Determination of the magnetic structure and confirmation of the presence or absence of inversion(P)and time reversal(Τ)symmetry is imperative for correctly understanding the topological magnetic materials.Here highqu...Determination of the magnetic structure and confirmation of the presence or absence of inversion(P)and time reversal(Τ)symmetry is imperative for correctly understanding the topological magnetic materials.Here highquality single crystals of the layered manganese pnictide CaMnSb_(2)are synthesized using the self-flux method.展开更多
Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgA...Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg0.97Sb0.99, with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. Here, we report the average grain size of 24–28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron x-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg0.97Sb0.99.展开更多
Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a...Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a non-collinear antiferromagnetic(AFM)phase at room temperature(RT).Signifi-cantly,the discovery of novel materials with nearly zero thermal expansion(ZTE)property near RT is required and pursued for avoiding thermal stress and fracture in spintronic devices.Herein,the doping of Sn(Ge)at the Ag site in the triangular lattice Mn_(3)Ag_(1-x)Sn(Ge)_(x)N compounds increases effectively the Neel point and makes the interesting non-collinearГ^(5g)AFM phase exist above RT.The magnetic phase diagrams withГ^(5g)phase up to 498 K were built by the combined analysis of neutron powder diffraction(NPD),magnetic measurements,electronic transport,and differential scanning calorimetry(DSC).The thermal expansion behaviors of Mn_(3)Ag_(1-x)Sn(Ge)_(x)N were modulated,and the nearly ZTE above RT was achieved in Mn_(3)Ag_(0.5)Ge_(0.5)N withinГ^(5g)AFM ordering.Our findings offer an effective way to tailor the non-collinear AFM ordering and correlated thermal expansion behavior for potential use in the emerging field of thermal stress-free magnetic chip materials.展开更多
During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other...During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other than advanced battery materials,in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery.Advanced characterization techniques,especially neutron-based techniques,have greatly promoted Li-ion battery researches.In this review,the characteristics or capabilities of various neutron-based characterization techniques,including elastic neutron scattering,quasi-elastic neutron scattering,neutron imaging,and inelastic neutron scattering,for the related Li-ion-battery researches are summarized.The design of in-situ/operando environment is also discussed.The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.展开更多
The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bu...The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material,which could be benefited from pulsed neutron source.Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source.The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15%by the time-of-flight neutron Bragg-edge imaging on this system.The results show its great potential applications in materials science and engineering.展开更多
Cobalt oxide,as one of the most fascinating examples of correlated electronic system,exhibits several exotic transport characteristics,such as superconductivity,charge ordering,and topological frustration.In this stud...Cobalt oxide,as one of the most fascinating examples of correlated electronic system,exhibits several exotic transport characteristics,such as superconductivity,charge ordering,and topological frustration.In this study,we are reporting the observation of another intriguing transport phenomenon in calcium cobaltates.Specifically,under a large magnetic field of 7 T,we observed an anomalously enhanced thermal conductivity that was accompanied with a largely suppressed thermopower.This observation reveals a hitherto undiscovered correlation between the two transport factors.Within the premise of Heisenberg model,we have shown that the observed experimental results can be explained consistently only if the magnon excitation is taken into account.Our study offers an insight into the puzzling origin of large thermopower observed in layered cobaltates and provides a specific strategy for further optimization of thermopower.展开更多
A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal st...A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal structure consists of shifted Cs,K,Bi,and Cl sites from the ideal positions with fractional occupancy in compensation,leading to variable local coordination of Cs^(+)ions,as revealed by^(133)Cs solid-state nuclear magnetic resonance spectroscopy.Cs_(2)KBiCl_(6) displays volume hysteresis at 5-298 K range upon heating and cooling.The Cs_(2)KBiCl_(6) has a direct bandgap of 3.35(2)eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue.The stabilization of disordered structure in Cs_(2)KBiCl_(6) is related to two factors including the large-sized K^(+)cation which prefers to coordinate with more than six Cl^(-),and the Bi^(3+)with 6s^(2) lone pair which has a preference for a local asymmetric environment.These findings could have general application and help to understand the structure and property of halide perovskites.展开更多
After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the ...After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the superconducting Cooper pairs.The recent discovery of high-temperature superconductivity near 80 K in the bilayer nickelate La_(3)Ni_(2)O_(7)under pressure provides a new platform to elucidate the origins of high-temperature superconductivity.We perform elastic and inelastic neutron scattering studies on a polycrystalline sample of La_(3)Ni_(2)O_(7-δ)at ambient pressure.No magnetic order can be identified down to 10 K.The absence of long-range magnetic order in neutron diffraction measurements may be ascribed to the smallness of the magnetic moment.However,we observe a weak flat spin-fluctuation signal in the inelastic scattering spectra at~45 meV.The observed spin excitations could be interpreted as a result of strong interlayer and weak intralayer magnetic couplings for stripe-type antiferromagnetic orders.Our results provide crucial information on the spin dynamics and are thus important for understanding the superconductivity in La_(3)Ni_(2)O_(7).展开更多
Materials with intrinsically low thermal conductivity are of fundamental interests.Here we report a new sort of simple one-dimensional(1 D)crystal structured bismuth selenohalides(Bi Se X,X=Br,I)with extremely low the...Materials with intrinsically low thermal conductivity are of fundamental interests.Here we report a new sort of simple one-dimensional(1 D)crystal structured bismuth selenohalides(Bi Se X,X=Br,I)with extremely low thermal conductivity of^0.27 W m^-1K^-1 at 573 K.The mechanism of the extremely low thermal conductivity in 1 D Bi Se X is elucidated systematically using the first-principles calculations,neutron powder-diffraction measurements and temperature tunable aberration-corrected scanning transmission electron microscopy(STEM).Results reveal that the1 D structure of Bi Se X possesses unique soft bonding character,low phonon velocity,strong anharmonicity of both acoustic and optical phonon modes,and large off-center displacement of Bi and halogen atoms.Cooperatively,all these features contribute to the minimal phonon transport.These findings provide a novel selection rule to search low thermal conductivity materials with potential applications in thermoelectrics and thermal barrier coatings.展开更多
We report a study of the structure and magnetic properties of the S=3/2 zigzag spin chain compound BaCoTe_(2)O_(7).Neutron diffraction measurements show that it crystallizes in the noncentrosymmetric space group Ama2 ...We report a study of the structure and magnetic properties of the S=3/2 zigzag spin chain compound BaCoTe_(2)O_(7).Neutron diffraction measurements show that it crystallizes in the noncentrosymmetric space group Ama2 with a canted↑↑↓↓spin structure along the quasi-one-dimensional zigzag chain and a moment size of 1.89(2)μBat 2 K.Both magnetic susceptibility and specific heat measurements yield an antiferromagnetic phase transition at TN=6.2 K.A negative Curie-Weiss temperature,ΘCW=-74.7(2) K,and an empirical frustration parameter,f=|ΘCW|/TN≈12,are obtained by fitting the magnetic susceptibility,indicating antiferromagnetic interactions and strong magnetic frustration.From ultraviolet-visible absorption spectroscopy and first-principles calculations,an indirect band gap of 2.68(2) eV is determined.We propose that the canted zigzag spin chain of BaCoTe_(2)O_(7) may produce a change in the polarization via the exchange-striction mechanism.展开更多
Nonlinear optical(NLO)switchable materials have attracted intense attention because of their promising applications in optoelectronic devices.However,previous studies are mainly limited to molecular-based compounds th...Nonlinear optical(NLO)switchable materials have attracted intense attention because of their promising applications in optoelectronic devices.However,previous studies are mainly limited to molecular-based compounds that usually exhibit narrow bandgaps.Here,we report all-inorganic Li_(9)Na_(3)Rb_(2)(SO_(4))_(7) as an ultrawide-bandgap NLO switchable material.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.12074023,12304053,and 12174018)the Large Scientific Facility Open Subject of Songshan Lake(Dongguan,Guangdong)the Fundamental Research Funds for the Central Universities in China。
文摘Determination of the magnetic structure and confirmation of the presence or absence of inversion(P)and time reversal(Τ)symmetry is imperative for correctly understanding the topological magnetic materials.Here highquality single crystals of the layered manganese pnictide CaMnSb_(2)are synthesized using the self-flux method.
基金Project supported by the National Natural Science Foundation of China(Grant No.11675255)the National Key R&D Program of China(Grant No.2016YFA0401503).
文摘Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg0.97Sb0.99, with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. Here, we report the average grain size of 24–28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron x-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg0.97Sb0.99.
基金supported by the financial support of National Key R&D Program of China(2022YFA1402600)National Natural Science Foundation of China(NSFC)(52272264)+1 种基金Sino-German Mobility Programme Project(M-0273)the Guangdong Basic and Applied Basic Research Foundation(2022A1515140117).
文摘Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spin-tronic phenomena owing to their strong spin-orbit coupling(SOC)and unique Berry phase.It is thus important to obtain a non-collinear antiferromagnetic(AFM)phase at room temperature(RT).Signifi-cantly,the discovery of novel materials with nearly zero thermal expansion(ZTE)property near RT is required and pursued for avoiding thermal stress and fracture in spintronic devices.Herein,the doping of Sn(Ge)at the Ag site in the triangular lattice Mn_(3)Ag_(1-x)Sn(Ge)_(x)N compounds increases effectively the Neel point and makes the interesting non-collinearГ^(5g)AFM phase exist above RT.The magnetic phase diagrams withГ^(5g)phase up to 498 K were built by the combined analysis of neutron powder diffraction(NPD),magnetic measurements,electronic transport,and differential scanning calorimetry(DSC).The thermal expansion behaviors of Mn_(3)Ag_(1-x)Sn(Ge)_(x)N were modulated,and the nearly ZTE above RT was achieved in Mn_(3)Ag_(0.5)Ge_(0.5)N withinГ^(5g)AFM ordering.Our findings offer an effective way to tailor the non-collinear AFM ordering and correlated thermal expansion behavior for potential use in the emerging field of thermal stress-free magnetic chip materials.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFA0401503)the National Materials Genome Project of China(Grant No.2016YFB0100106)the National Natural Science Foundation of China(Grant No.11675255)
文摘During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other than advanced battery materials,in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery.Advanced characterization techniques,especially neutron-based techniques,have greatly promoted Li-ion battery researches.In this review,the characteristics or capabilities of various neutron-based characterization techniques,including elastic neutron scattering,quasi-elastic neutron scattering,neutron imaging,and inelastic neutron scattering,for the related Li-ion-battery researches are summarized.The design of in-situ/operando environment is also discussed.The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0701903 and 2016YFA0401502)the National Natural Science Foundation of China(Grant No.12041202)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017023)the Guangdong Natural Science Foundation,China(Grant No.2016A030313129)the Department of Science and Technology of Guangdong Province under grant project of energy-resolved neutron imaging instrument.
文摘The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material,which could be benefited from pulsed neutron source.Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source.The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15%by the time-of-flight neutron Bragg-edge imaging on this system.The results show its great potential applications in materials science and engineering.
基金the supports from National Natural Science Foundation of China through grant#52002383Ningbo Municipal Bureau of Science and Technology through grant#202003N4365+1 种基金supported by National Natural Science Foundation of China(Grant No.52001012)Beijing Natural Science Foundation(Grant No.2214070).
文摘Cobalt oxide,as one of the most fascinating examples of correlated electronic system,exhibits several exotic transport characteristics,such as superconductivity,charge ordering,and topological frustration.In this study,we are reporting the observation of another intriguing transport phenomenon in calcium cobaltates.Specifically,under a large magnetic field of 7 T,we observed an anomalously enhanced thermal conductivity that was accompanied with a largely suppressed thermopower.This observation reveals a hitherto undiscovered correlation between the two transport factors.Within the premise of Heisenberg model,we have shown that the observed experimental results can be explained consistently only if the magnon excitation is taken into account.Our study offers an insight into the puzzling origin of large thermopower observed in layered cobaltates and provides a specific strategy for further optimization of thermopower.
基金the National Science Foundation of China(Nos.22090043 and 22161014)Guangxi Natural Science Foundation(Nos.2019GXNSFGA245006 and 2020GXNSFAA297220)the Foundation of Guilin University of Technology(No.GUTQDJJ2018115)for the financial support。
文摘A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal structure consists of shifted Cs,K,Bi,and Cl sites from the ideal positions with fractional occupancy in compensation,leading to variable local coordination of Cs^(+)ions,as revealed by^(133)Cs solid-state nuclear magnetic resonance spectroscopy.Cs_(2)KBiCl_(6) displays volume hysteresis at 5-298 K range upon heating and cooling.The Cs_(2)KBiCl_(6) has a direct bandgap of 3.35(2)eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue.The stabilization of disordered structure in Cs_(2)KBiCl_(6) is related to two factors including the large-sized K^(+)cation which prefers to coordinate with more than six Cl^(-),and the Bi^(3+)with 6s^(2) lone pair which has a preference for a local asymmetric environment.These findings could have general application and help to understand the structure and property of halide perovskites.
基金supported by the National Key Research and Development Program of China(2023YFA1406500,2023YFA1406000)the National Natural Science Foundation of China(12304187,12174454,U21301001)+5 种基金the Guangdong Basic and Applied Basic Research Funds(2024B1515020040,2024A1515030030,2022A1515011618)Guangzhou Basic and Applied Basic Research Funds(202201011123,2024A04J4024,2024A04J6417)Shenzhen Science and Technology Program(RCYX20231211090245050)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(2022B1212010008)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(23qnpy57)the open research fund of Songshan Lake Materials Laboratory(2023SLABFN30)。
文摘After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the superconducting Cooper pairs.The recent discovery of high-temperature superconductivity near 80 K in the bilayer nickelate La_(3)Ni_(2)O_(7)under pressure provides a new platform to elucidate the origins of high-temperature superconductivity.We perform elastic and inelastic neutron scattering studies on a polycrystalline sample of La_(3)Ni_(2)O_(7-δ)at ambient pressure.No magnetic order can be identified down to 10 K.The absence of long-range magnetic order in neutron diffraction measurements may be ascribed to the smallness of the magnetic moment.However,we observe a weak flat spin-fluctuation signal in the inelastic scattering spectra at~45 meV.The observed spin excitations could be interpreted as a result of strong interlayer and weak intralayer magnetic couplings for stripe-type antiferromagnetic orders.Our results provide crucial information on the spin dynamics and are thus important for understanding the superconductivity in La_(3)Ni_(2)O_(7).
基金supported by the National Key Research and Development Program of China(2018YFA0702100 and 2018YFB0703600)the National Natural Science Foundation of China(51772012 and 51632005)+5 种基金Shenzhen Peacock Plan team(KQTD2016022619565991)Beijing Natural Science Foundation(JQ18004)China Postdoctoral Science Foundation Grant(2019M650429)111 Project(B17002)the National Science Foundation for Distinguished Young Scholars(51925101)the financial support from Singapore Ministry of Education Tier 1grant(R-284-000-212-114)for Lee Kuan Yew Postdoctoral Fellowship。
文摘Materials with intrinsically low thermal conductivity are of fundamental interests.Here we report a new sort of simple one-dimensional(1 D)crystal structured bismuth selenohalides(Bi Se X,X=Br,I)with extremely low thermal conductivity of^0.27 W m^-1K^-1 at 573 K.The mechanism of the extremely low thermal conductivity in 1 D Bi Se X is elucidated systematically using the first-principles calculations,neutron powder-diffraction measurements and temperature tunable aberration-corrected scanning transmission electron microscopy(STEM).Results reveal that the1 D structure of Bi Se X possesses unique soft bonding character,low phonon velocity,strong anharmonicity of both acoustic and optical phonon modes,and large off-center displacement of Bi and halogen atoms.Cooperatively,all these features contribute to the minimal phonon transport.These findings provide a novel selection rule to search low thermal conductivity materials with potential applications in thermoelectrics and thermal barrier coatings.
基金supported by the National Natural Science Foundation of China(Grant No.11904414)the National Key Research and Development Program of China(Grant No.2019YFA0705702)+3 种基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0306001,and 2017YFA0206203)the National Natural Science Foundation of China(Grant No.11974432)the Guangdong Basic and Applied Basic Research Fund(Grant No.2019A1515011337)the Leading Talent Program of Guangdong Special Projects。
文摘We report a study of the structure and magnetic properties of the S=3/2 zigzag spin chain compound BaCoTe_(2)O_(7).Neutron diffraction measurements show that it crystallizes in the noncentrosymmetric space group Ama2 with a canted↑↑↓↓spin structure along the quasi-one-dimensional zigzag chain and a moment size of 1.89(2)μBat 2 K.Both magnetic susceptibility and specific heat measurements yield an antiferromagnetic phase transition at TN=6.2 K.A negative Curie-Weiss temperature,ΘCW=-74.7(2) K,and an empirical frustration parameter,f=|ΘCW|/TN≈12,are obtained by fitting the magnetic susceptibility,indicating antiferromagnetic interactions and strong magnetic frustration.From ultraviolet-visible absorption spectroscopy and first-principles calculations,an indirect band gap of 2.68(2) eV is determined.We propose that the canted zigzag spin chain of BaCoTe_(2)O_(7) may produce a change in the polarization via the exchange-striction mechanism.
基金supported by the National Nature Science Foundation of China(21833010,61975207,21622101,21921001,21525104,and 51662013)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000 and XDB20010200)+5 种基金the Natural Science Foundation of Fujian Province(2018H0047)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(ZDBS-LY-SLH024)the Natural Science Foundation of Guangxi Province(2018GXNSFDA281015)the National Key Research and Development Program of China(2019YFA0210400)Key Laboratory of Functional Crystals and Laser Technology,TIPC,CAS(FCLT 202003)Key Laboratory of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education/Guangxi Key Laboratory of Optical and Electronic Materials and Devices(20KF-11).
文摘Nonlinear optical(NLO)switchable materials have attracted intense attention because of their promising applications in optoelectronic devices.However,previous studies are mainly limited to molecular-based compounds that usually exhibit narrow bandgaps.Here,we report all-inorganic Li_(9)Na_(3)Rb_(2)(SO_(4))_(7) as an ultrawide-bandgap NLO switchable material.
