Thermal expansion is an essential issue in the field of materials science and engineering.Investigation of anomalous thermal expansion is beneficial to controlling it and developing related functions.Here,we report di...Thermal expansion is an essential issue in the field of materials science and engineering.Investigation of anomalous thermal expansion is beneficial to controlling it and developing related functions.Here,we report disitinctly anisotropic thermal expansion of CrB_(2)via temperature dependence of neutron diffraction,in which positive thermal expansion is observed within basal plane whereas negative thermal expansion emerges along the c direction.Intriguingly,zero thermal expansion of unit cell volume is determined from 5 to 130 K with the coefficient of thermal expansion ofāv=0.4(1)×10^(-6)K^(-1).Magnetization measurement shows there is an antiferromagnetic-paramagnetic transition near 90 K,which may correlate to the thermal expansion anomaly.DFT calculations identify no chemical binding of Cr-Cr pair,implying such antiferromagnetic ordering originates from the double exchange interaction of Cr-B-Cr.展开更多
Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and c...Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and charge upon heating,have limited the ZTE alloys by very few numbers of species.In this work,we report a route to achieving twodimensional(2D)ZTE behavior by regulating crystallographic texture and magneto-volume effects(MVEs)in volumetric positive thermal expansion alloys.This is illustrated in a series of Mn_(x)Fe_(5-x)Si_(3)compounds by those earth-abundant elements.As a result,a 2D ZTE performance with a coefficient of thermal expansion α_(1)=0.45×10^(-7)K^(-1) over a broad temperature window of 10–310 K was observed in MnFe4Si3.The experimental results by synchrotron X-ray diffraction,neutron diffraction,microscopy,and magnetization measurements reveal that such a ZTE behavior is strongly coupled with fiber crystallographic texture and magnetic moment at the crystallographic 6g site that dominates MVEs in the a-b plane.The competition between ferromagnetic Fe_(4d)–Fe_(6g)(J_(FM))and antiferromagnetic Mn_(4d)–Mn_(6g)(J_(AFM))interactions makes the Mn_(1.5)Fe_(3.5)Si_(3) and Mn_(2)Fe_(3)Si_(3)compounds show mixed magnetism and negative thermal expansion(NTE).The integral approach presented here can be used to extend the scope of ZTE/NTE species in other magnetic or ferroelectric materials.展开更多
Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and te...Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and temperature windows.In this study,we report a novel class of near-zero thermal expansion(near ZTE)alloys,ErFe_(10)V_(2−x)Mo_(x),over a wide temperature range(120–440 K).Neutron diffraction and magnetic measurements demonstrated that the ErFe_(10)V_(2−x)Mo_(x)compounds exhibited complex ferrimagnetic(FIM)structures below Curie temperature(TC).The near-ZTE behaviors were closely related to the itinerant Fe 3d moments in the collinear FIM states,as well as the geometric[−Fe−Fe−]linkages.Further,X-ray absorption near-edge structure(XANES)spectra revealed that the nonmagnetic substitution changed the electronic valence states of Fe atoms,which,in turn,changed Fe 3d moments and TC,hence,regulating the thermal expansion behaviors.Our work provides an insight into chemical modifications of thermal expansion in magnetic intermetallic compounds.展开更多
基金supported by National Key R&D Program of China(2020YFA0406202)National Natural Science Foundation of China(22090042,21731001,22275015 and 21971009)Neutron diffraction experiments were carried out on WOMBAT in Australian Nuclear Science and Technology Organization(ANSTO).
文摘Thermal expansion is an essential issue in the field of materials science and engineering.Investigation of anomalous thermal expansion is beneficial to controlling it and developing related functions.Here,we report disitinctly anisotropic thermal expansion of CrB_(2)via temperature dependence of neutron diffraction,in which positive thermal expansion is observed within basal plane whereas negative thermal expansion emerges along the c direction.Intriguingly,zero thermal expansion of unit cell volume is determined from 5 to 130 K with the coefficient of thermal expansion ofāv=0.4(1)×10^(-6)K^(-1).Magnetization measurement shows there is an antiferromagnetic-paramagnetic transition near 90 K,which may correlate to the thermal expansion anomaly.DFT calculations identify no chemical binding of Cr-Cr pair,implying such antiferromagnetic ordering originates from the double exchange interaction of Cr-B-Cr.
基金supported by the National Key R&D Program of China(2020YFA0406202)the National Natural Science Foundation of China(22090042,21971009 and 21731001)+1 种基金the Fundamental Research Funds for the Central Universities,China(FRF-IDRY-19-018 and FRF-BR-19-003B)Neutron texture analysis was carried out at the Spallation Neutron Source(SNS)(Proposal No.2020B26069)。
文摘Zero thermal expansion(ZTE)alloys have unique aspects in the application of the engineering of precise dimensional control.However,the harsh conditions to realize ZTE,i.e.,appropriate coupling among spin,lattice,and charge upon heating,have limited the ZTE alloys by very few numbers of species.In this work,we report a route to achieving twodimensional(2D)ZTE behavior by regulating crystallographic texture and magneto-volume effects(MVEs)in volumetric positive thermal expansion alloys.This is illustrated in a series of Mn_(x)Fe_(5-x)Si_(3)compounds by those earth-abundant elements.As a result,a 2D ZTE performance with a coefficient of thermal expansion α_(1)=0.45×10^(-7)K^(-1) over a broad temperature window of 10–310 K was observed in MnFe4Si3.The experimental results by synchrotron X-ray diffraction,neutron diffraction,microscopy,and magnetization measurements reveal that such a ZTE behavior is strongly coupled with fiber crystallographic texture and magnetic moment at the crystallographic 6g site that dominates MVEs in the a-b plane.The competition between ferromagnetic Fe_(4d)–Fe_(6g)(J_(FM))and antiferromagnetic Mn_(4d)–Mn_(6g)(J_(AFM))interactions makes the Mn_(1.5)Fe_(3.5)Si_(3) and Mn_(2)Fe_(3)Si_(3)compounds show mixed magnetism and negative thermal expansion(NTE).The integral approach presented here can be used to extend the scope of ZTE/NTE species in other magnetic or ferroelectric materials.
基金supported by the National Natural Science Foundation of China(21701008,21231001,21590793,and 21731001)National Postdoctoral Program for Innovative Talents(BX201700027)the Fundamental Research Funds for the Central Universities,China(FRF-IDRY-19-018).
文摘Alloys with low thermal expansion could overcome thermal stress issues under temperature-fluctuated conditions and possess important application prospects,while they are restricted to finite chemical components and temperature windows.In this study,we report a novel class of near-zero thermal expansion(near ZTE)alloys,ErFe_(10)V_(2−x)Mo_(x),over a wide temperature range(120–440 K).Neutron diffraction and magnetic measurements demonstrated that the ErFe_(10)V_(2−x)Mo_(x)compounds exhibited complex ferrimagnetic(FIM)structures below Curie temperature(TC).The near-ZTE behaviors were closely related to the itinerant Fe 3d moments in the collinear FIM states,as well as the geometric[−Fe−Fe−]linkages.Further,X-ray absorption near-edge structure(XANES)spectra revealed that the nonmagnetic substitution changed the electronic valence states of Fe atoms,which,in turn,changed Fe 3d moments and TC,hence,regulating the thermal expansion behaviors.Our work provides an insight into chemical modifications of thermal expansion in magnetic intermetallic compounds.
