Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial...Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.展开更多
Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibri...Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.展开更多
采用快速液相烧结法制备Bi_(1-x)Pr_(x)Fe_(1-x)Ti_(x)O_(3)(x=0.00、0.03、0.06、0.12)系列多铁陶瓷样品,研究Pr-Ti共掺杂对BiFe O_(3)结构、缺陷、电学和磁学特性的影响。XRD分析结果表明:所有样品均为菱方钙钛矿结构,Pr-Ti共掺杂可...采用快速液相烧结法制备Bi_(1-x)Pr_(x)Fe_(1-x)Ti_(x)O_(3)(x=0.00、0.03、0.06、0.12)系列多铁陶瓷样品,研究Pr-Ti共掺杂对BiFe O_(3)结构、缺陷、电学和磁学特性的影响。XRD分析结果表明:所有样品均为菱方钙钛矿结构,Pr-Ti共掺杂可有效抑制杂相生成,当掺杂量高于0.06时杂相基本消失,共掺杂引起结构畸变。正电子湮没寿命谱测试结果表明:所有样品中均存在阳离子空位型缺陷,空位尺寸和浓度均随Pr-Ti掺杂量增加而增大。电学和磁学性能测试结果表明:适量Pr-Ti共掺杂可有效提高Bi Fe O_(3)的介电、铁电和磁学性能。综合上述结果,认为BiFeO_(3)多铁性能的改善可能是由于Pr-Ti共掺杂引起晶格畸变、减少氧空位浓度、改变阳离子空位浓度等多种原因引起。展开更多
The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a co...The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a constant.By X-ray diffraction and ther- momagnetic measurements,the crystalline phases of the alloys,an unknown phase and α-(Fe,Ga)besides Fe_3 B as major one,were identified.The relationship between room temperature coercive field and Ga.content was also studied.展开更多
The magnetostriction and acoustics properties of Tb1-x xDyx (Fe1-yMny) 1.95 alloys and their application to sonar transducers were studied. The following results were obtained from experiments. When the applied magn...The magnetostriction and acoustics properties of Tb1-x xDyx (Fe1-yMny) 1.95 alloys and their application to sonar transducers were studied. The following results were obtained from experiments. When the applied magnetic field intensity is ≥ 800 kA·m-1, the magnetostrictive coefficients are (1300- 1800)× 10-6. The electromechanical coupling factors are 0.84-0.93, the sound velocities 2168-2856 m·s-1 and the Young's modulus (5.06- 7.26) ×10 N·m-2. A sonar transducer made of the alloy rod, which has a total length of 300 mm and a total weight of 2 kg, is characterized by 2.4 kHz specified resonant frequency, 1 kHz frequency band, 173 kB current response and 45% electroacoustic efficiency.展开更多
The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and...The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and the presence of α-Fe, Nd2Fe14B and Fe2B phases in the samples with x > 0.1. The magnetic measurement shows that Curie temperutures of Fe3B and Nd2Fe14B phases decrease with increasing Cr content. The influence of the substitution of Cr for Fe was discussed.展开更多
The effect of substitution of Fe^(3+) by Al^(3+) on the structure and magnetic properties of NdAl_(x)Fe_(1-x)O_(3) perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion...The effect of substitution of Fe^(3+) by Al^(3+) on the structure and magnetic properties of NdAl_(x)Fe_(1-x)O_(3) perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was studied.All samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples were investigated using a vibrating sample magnetometer(VSM).The X-ray results for all samples reveal the formation of an orthorhombic perovskite phase(space group Pbnm) with no secondary phase.The crystallite sizes of the nanoparticles are found to decrease with increasing Al content,and are in the range of 53-38 nm.SEM images show spherical nanoparticles with agglomeration.The FT-IR spectra confirm the presence of metal oxygen bonds.The M-H loop of the pristine NdFeO_(3) sample is antiferromagnetic in the a b plane with weak ferromagnetism in the c-axis.Introducing AI inclusions in the pristine polycrystal thereby creating magnetic vacancies is seen to influence the magnetic properties.The magnetic dilution results in enhanced magnetisation at low Al content;x=0.1,0.2(saturation magnetisation being 2.08 and 2.05 emu/g,respectively) compared to the pristine sample with a saturation magnetisation of 1.43 emu/g due to increased exchange interaction.Also dilution with nonmagnetic dopant induces the phase transition from weak ferromagnetic to paramagnetic depending on the impurity concentration.The coercive field for NdFeO_(3) is found to be equal to 1950 Oe and decreases with Al-substitution.These findings lay a ground work for research in tuning magnetic properties and in spintronics with potential applications in data storage,switches and electronic devices.展开更多
The magnetic refrigeration(MR)utilizing magnetocaloric effect(MCE)has been recognized as an environmentally friendly and energy efficiency technology.Here we presented the magnetic properties and MCE in Pr-doped La_(1...The magnetic refrigeration(MR)utilizing magnetocaloric effect(MCE)has been recognized as an environmentally friendly and energy efficiency technology.Here we presented the magnetic properties and MCE in Pr-doped La_(1-x)Pr_(x)Fe_(12)B_(6)(x=0.05-0.2)itinerant-electron metamagnetic(IEM)compounds.A small amount of Pr doping La site can greatly improve the peak values in the magnetic entropy change S_(M)(T)curves,especially under relatively low magnetic field changes(ΔH).Additionally,the peak temperature increases gradually and the magnetic hysteresis reduces gradually with increasing x.The observed MCE in present La_(1-x)Pr_(x)Fe_(12)B_(6)compounds is related to its field-induced first-ordered IEM transition.The peak values ofΔS_(M)for La_(1-x)Pr_(x)Fe_(12)B_(6)compounds reach 13.4,15.4,12.5 and 13.0 J/(kg K)at T_(C)~58,68,72and 89 K for x=0.05,0.10,0.15 and 0.2 under H of 0-7 T,respectively.The corresponding relative cooling power values are 462.3,480.7,372.4 and 375.7 J/kg.The present La_(1-x)Pr_(x)Fe_(12)B_(6)compounds could be good candidates for active MR application if the magnetic and thermal hysteresis can be further reduced.The present work indicates that the La Fe_(12)B_(6)-based material system could also exhibit promising magnetocaloric performances.展开更多
Fe_(y)Te_(1-x)Se_(x),an archetypical iron-based high-temperature superconductor with a simple structure but rich physical properties,has attracted lots of attention because the two end compositions,Se content x=0 and ...Fe_(y)Te_(1-x)Se_(x),an archetypical iron-based high-temperature superconductor with a simple structure but rich physical properties,has attracted lots of attention because the two end compositions,Se content x=0 and 1,exhibit antiferromagnetism and nematicity,respectively,making it an ideal candidate for studying their interactions with superconductivity.However,what is clearly lacking to date is a complete phase diagram of Fe_(y)Te_(1-x)Se_(x)as functions of its chemical compositions since phase separation usually occurs from x~0.6 to 0.9 in bulk crystals.Moreover,fine control of its composition is experimentally challenging because both Te and Se are volatile elements.Here we establish a complete phase diagram of Fe_(y)Te_(1-x)Se_(x),achieved by high-throughput film synthesis and characterization techniques.An advanced combinatorial synthesis process enables us to fabricate an epitaxial composition-spread Fe_(y)Te_(1-x)Se_(x)film encompassing the entire Se content x from 0 to 1 on a single piece of CaFsubstrate.The micro-region composition analysis and X-ray diffraction show a successful continuous tuning of chemical compositions and lattice parameters,respectively.The micro-scale pattern technique allows the mapping of electrical transport properties as a function of relative Se content with an unprecedented resolution of0.0074.Combining with the spin patterns in literature,we build a detailed phase diagram that can unify the electronic and magnetic properties of Fe_(y)Te_(1-x)Se_(x).Our composition-spread Fe_(y)Te_(1-x)Se_(x) films,overcoming the challenges of phase separation and precise control of chemical compositions,provide an ideal platform for studying the relationship between superconductivity and magnetism.展开更多
Polycrystalline YMn1?xFexO3 (0 < x < 0.1) samples are synthesized by solid-state reaction method and characterized by X-ray diffraction. The X-ray diffraction patterns indicate that YMn1?xFexO3 compounds maintai...Polycrystalline YMn1?xFexO3 (0 < x < 0.1) samples are synthesized by solid-state reaction method and characterized by X-ray diffraction. The X-ray diffraction patterns indicate that YMn1?xFexO3 compounds maintain hexagonal structure with space group of p63 cm. Ferromagnetism of YMn1?xFexO3 increases with increasing doping concentration of Fe3+, attributed to the suppression of the frustration and the change of the Mn-O bond length certificated by XAS analysis.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51804116,51772092,51972109)Hunan Provincial Natural Science Foundation of China(Nos.2018JJ3207,2017JJ2103,2019JJ40102,2019JJ50205,2018JJ2149)+1 种基金China Scholarship Councilthe Scientific Research Fund of Hunan Provincial Education Department,China(Nos.18B346,18A315,18B347,19A205)。
文摘Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.
基金financially supported by the National Natural Science Foundation of China(No.51904250)the China Postdoctoral Science Foundation(No.2021M692254)+2 种基金the Sichuan Science and Technology Program(No.2022YFG0098)the Fundamental Research Funds for the Central Universities(Nos.2021CDSN-02,2022SCU12002,2022CDZG-17,2022CDSN-08,2022CDZG-9)the Hohhot Science and Technology Program(No.2023-Jie Bang Gua Shuai-Gao-3)。
文摘Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.
文摘采用快速液相烧结法制备Bi_(1-x)Pr_(x)Fe_(1-x)Ti_(x)O_(3)(x=0.00、0.03、0.06、0.12)系列多铁陶瓷样品,研究Pr-Ti共掺杂对BiFe O_(3)结构、缺陷、电学和磁学特性的影响。XRD分析结果表明:所有样品均为菱方钙钛矿结构,Pr-Ti共掺杂可有效抑制杂相生成,当掺杂量高于0.06时杂相基本消失,共掺杂引起结构畸变。正电子湮没寿命谱测试结果表明:所有样品中均存在阳离子空位型缺陷,空位尺寸和浓度均随Pr-Ti掺杂量增加而增大。电学和磁学性能测试结果表明:适量Pr-Ti共掺杂可有效提高Bi Fe O_(3)的介电、铁电和磁学性能。综合上述结果,认为BiFeO_(3)多铁性能的改善可能是由于Pr-Ti共掺杂引起晶格畸变、减少氧空位浓度、改变阳离子空位浓度等多种原因引起。
文摘The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a constant.By X-ray diffraction and ther- momagnetic measurements,the crystalline phases of the alloys,an unknown phase and α-(Fe,Ga)besides Fe_3 B as major one,were identified.The relationship between room temperature coercive field and Ga.content was also studied.
基金the Rare Earth Office of MMI and the National Natural Science Foundation of China!59501008
文摘The magnetostriction and acoustics properties of Tb1-x xDyx (Fe1-yMny) 1.95 alloys and their application to sonar transducers were studied. The following results were obtained from experiments. When the applied magnetic field intensity is ≥ 800 kA·m-1, the magnetostrictive coefficients are (1300- 1800)× 10-6. The electromechanical coupling factors are 0.84-0.93, the sound velocities 2168-2856 m·s-1 and the Young's modulus (5.06- 7.26) ×10 N·m-2. A sonar transducer made of the alloy rod, which has a total length of 300 mm and a total weight of 2 kg, is characterized by 2.4 kHz specified resonant frequency, 1 kHz frequency band, 173 kB current response and 45% electroacoustic efficiency.
文摘The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and the presence of α-Fe, Nd2Fe14B and Fe2B phases in the samples with x > 0.1. The magnetic measurement shows that Curie temperutures of Fe3B and Nd2Fe14B phases decrease with increasing Cr content. The influence of the substitution of Cr for Fe was discussed.
文摘The effect of substitution of Fe^(3+) by Al^(3+) on the structure and magnetic properties of NdAl_(x)Fe_(1-x)O_(3) perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was studied.All samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples were investigated using a vibrating sample magnetometer(VSM).The X-ray results for all samples reveal the formation of an orthorhombic perovskite phase(space group Pbnm) with no secondary phase.The crystallite sizes of the nanoparticles are found to decrease with increasing Al content,and are in the range of 53-38 nm.SEM images show spherical nanoparticles with agglomeration.The FT-IR spectra confirm the presence of metal oxygen bonds.The M-H loop of the pristine NdFeO_(3) sample is antiferromagnetic in the a b plane with weak ferromagnetism in the c-axis.Introducing AI inclusions in the pristine polycrystal thereby creating magnetic vacancies is seen to influence the magnetic properties.The magnetic dilution results in enhanced magnetisation at low Al content;x=0.1,0.2(saturation magnetisation being 2.08 and 2.05 emu/g,respectively) compared to the pristine sample with a saturation magnetisation of 1.43 emu/g due to increased exchange interaction.Also dilution with nonmagnetic dopant induces the phase transition from weak ferromagnetic to paramagnetic depending on the impurity concentration.The coercive field for NdFeO_(3) is found to be equal to 1950 Oe and decreases with Al-substitution.These findings lay a ground work for research in tuning magnetic properties and in spintronics with potential applications in data storage,switches and electronic devices.
基金supported by the National Natural Science Foundation of China(No.91963123)the Ten Thousand Talents Plan of Zhejiang Province of China(No.2018R52003)。
文摘The magnetic refrigeration(MR)utilizing magnetocaloric effect(MCE)has been recognized as an environmentally friendly and energy efficiency technology.Here we presented the magnetic properties and MCE in Pr-doped La_(1-x)Pr_(x)Fe_(12)B_(6)(x=0.05-0.2)itinerant-electron metamagnetic(IEM)compounds.A small amount of Pr doping La site can greatly improve the peak values in the magnetic entropy change S_(M)(T)curves,especially under relatively low magnetic field changes(ΔH).Additionally,the peak temperature increases gradually and the magnetic hysteresis reduces gradually with increasing x.The observed MCE in present La_(1-x)Pr_(x)Fe_(12)B_(6)compounds is related to its field-induced first-ordered IEM transition.The peak values ofΔS_(M)for La_(1-x)Pr_(x)Fe_(12)B_(6)compounds reach 13.4,15.4,12.5 and 13.0 J/(kg K)at T_(C)~58,68,72and 89 K for x=0.05,0.10,0.15 and 0.2 under H of 0-7 T,respectively.The corresponding relative cooling power values are 462.3,480.7,372.4 and 375.7 J/kg.The present La_(1-x)Pr_(x)Fe_(12)B_(6)compounds could be good candidates for active MR application if the magnetic and thermal hysteresis can be further reduced.The present work indicates that the La Fe_(12)B_(6)-based material system could also exhibit promising magnetocaloric performances.
基金supported by the National Key R&D Program of China(2021YFA0718700,2017YFA0302902,2017YFA0303003,and 2018YFB0704102)the National Natural Science Foundation of China(11834016,11961141008,11927808,and 12174428)+3 种基金the Strategic Priority Research Program(B)of Chinese Academy of Sciences(XDB25000000 and XDB33000000)the Beijing Natural Science Foundation(Z190008)CAS Interdisciplinary Innovation Team,Key-Area Research and Development Program of Guangdong Province(2020B0101340002)the Center for Materials Genome。
文摘Fe_(y)Te_(1-x)Se_(x),an archetypical iron-based high-temperature superconductor with a simple structure but rich physical properties,has attracted lots of attention because the two end compositions,Se content x=0 and 1,exhibit antiferromagnetism and nematicity,respectively,making it an ideal candidate for studying their interactions with superconductivity.However,what is clearly lacking to date is a complete phase diagram of Fe_(y)Te_(1-x)Se_(x)as functions of its chemical compositions since phase separation usually occurs from x~0.6 to 0.9 in bulk crystals.Moreover,fine control of its composition is experimentally challenging because both Te and Se are volatile elements.Here we establish a complete phase diagram of Fe_(y)Te_(1-x)Se_(x),achieved by high-throughput film synthesis and characterization techniques.An advanced combinatorial synthesis process enables us to fabricate an epitaxial composition-spread Fe_(y)Te_(1-x)Se_(x)film encompassing the entire Se content x from 0 to 1 on a single piece of CaFsubstrate.The micro-region composition analysis and X-ray diffraction show a successful continuous tuning of chemical compositions and lattice parameters,respectively.The micro-scale pattern technique allows the mapping of electrical transport properties as a function of relative Se content with an unprecedented resolution of0.0074.Combining with the spin patterns in literature,we build a detailed phase diagram that can unify the electronic and magnetic properties of Fe_(y)Te_(1-x)Se_(x).Our composition-spread Fe_(y)Te_(1-x)Se_(x) films,overcoming the challenges of phase separation and precise control of chemical compositions,provide an ideal platform for studying the relationship between superconductivity and magnetism.
基金supported by the National Natural Science Foundation of China(U1232133).
文摘Polycrystalline YMn1?xFexO3 (0 < x < 0.1) samples are synthesized by solid-state reaction method and characterized by X-ray diffraction. The X-ray diffraction patterns indicate that YMn1?xFexO3 compounds maintain hexagonal structure with space group of p63 cm. Ferromagnetism of YMn1?xFexO3 increases with increasing doping concentration of Fe3+, attributed to the suppression of the frustration and the change of the Mn-O bond length certificated by XAS analysis.
