Sodium-ion capacitors(SICs)have great potential in energy storage due to their low cost,the abundance of Na,and the potential to deliver high energy and power simultaneously.This article demonstrates a template-assist...Sodium-ion capacitors(SICs)have great potential in energy storage due to their low cost,the abundance of Na,and the potential to deliver high energy and power simultaneously.This article demonstrates a template-assisted method to induce graphitic nanodomains and micro-mesopores into nitrogen-doped carbons.This study elucidates that these graphitic nanodomains are beneficial for Na+storage.The obtained N-doped carbon(As8Mg)electrode achieved a reversible capacity of 254 mA h g^(-1)at 0.1 A g^(-1).Moreover,the As8Mg-based SIC device achieves high combinations of power/energy densities(53 W kg^(-1)at 224 Wh kg^(-1)and 10410 W kg^(-1)at 51 Wh kg^(-1))with outstanding cycle stability(99.7%retention over 600 cycles at 0.2 A g^(-1)).Our findings provide insights into optimizing carbon’s microstructure to boost sodium storage in the pseudocapacitive mode.展开更多
Fe-based metallic glasses are promising functional materials for advanced magnetism and sensor fields.Tailoring magnetic performance in amorphous materials requires a thorough knowledge of the correlation between stru...Fe-based metallic glasses are promising functional materials for advanced magnetism and sensor fields.Tailoring magnetic performance in amorphous materials requires a thorough knowledge of the correlation between structural disorder and magnetic order,which remains ambiguous.Two practical difficulties remain:the first is directly observing subtle magnetic structural changes on multiple scales,and the second is precisely regulating the various amorphous states.Here we propose a novel approach to tailor the amorphous structure through the liquid-liquid phase transition.In-situ synchrotron diffraction has unraveled a medium-range ordering process dominated by edge-sharing cluster connectivity during the liquid-liquid phase transition.Moreover,nanodomains with topological order have been found to exist in composition with liquid-liquid phase transition,manifesting as hexagonal patterns in small-angle neutron scattering profiles.The liquid-liquid phase transition can induce the nanodomains to be more locally ordered,generating stronger exchange interactions due to the reduced Fe–Fe bond length and the enhanced structural order,leading to the increment of saturation magnetization.Furthermore,the increased local heterogeneity at the medium-range scale enhances the magnetic anisotropy,promoting the permeability response under applied stress and leading to a better stress-impedance effect.These experimental results pave the way to tailor the magnetic structure and performance through the liquid-liquid phase transition.展开更多
Conventional kinetics theory for diffusion-controlled phase transformation shows that the reverse transition should lag behind the temperature rise through rapid heating,i.e.,overheating is required.In this work,we fo...Conventional kinetics theory for diffusion-controlled phase transformation shows that the reverse transition should lag behind the temperature rise through rapid heating,i.e.,overheating is required.In this work,we found that theβ-transus temperature decreased by∼50℃ during studying theα→βtransformation in Ti-6Al-4V alloy via electropulsing treatment(EPT).The calculation suggests that the acceleration of transformation kinetics cannot be fully explained by Joule heat and athermal effects of the electromigration effect and electron wind theory.The microstructural evolution during EPT was systematically investigated utilizing scanning electron microscope(SEM),electron backscattered diffraction(EBSD),X-ray diffraction(XRD),transmission Kikuchi diffraction(TKD),and transmission electron micro-scope(TEM).Microscopic analysis shows that the nano-sizedωand O'phases formed in theβphase,which causes large numbers of lattice distortion regions.The defects are conducive to accelerating the bulk diffusion of alloying elements inβ.Moreover,the nanodomains limited the growth of martensite,therefore nanocrystalline martensite formed after quenching.These findings develop the understanding of the destructive effect of current on metallic crystal,which will help to guide microstructural regulation in titanium and other alloys.展开更多
The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)an...The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.展开更多
Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been fr...Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been frequently reported in HEAs,however,nanoscale microstructural phase evolution has not been investigated to the same extent.Herein,we have prepared the Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA and investi-gated the strain glass transition and its associated properties using dynamic mechanical analysis and mi-crostructure characterization.We have found that the elastic modulus in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA deviates from Wachtman’s equation and observed the Elinvar effect in the form of temperature-independent mod-ulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 K.The strain glass transition has been evidenced in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy(TEM)cooling,and substantiated by the broken ergodicity during zero-field-cooling/field-cooling.The strain glass transition is believed to account for the Elinvar effect,where the modulus hardening of nano-sized domains compensates dynam-ically with the modulus softening of the transformable matrix.展开更多
The soybean root system is complex.In addition to being composed of various cell types,the soybean root system includes the primary root,the lateral roots,and the nodule,an organ in which mutualistic symbiosis with N-...The soybean root system is complex.In addition to being composed of various cell types,the soybean root system includes the primary root,the lateral roots,and the nodule,an organ in which mutualistic symbiosis with N-fixing rhizobia occurs.A mature soybean root nodule is characterized by a central infection zone where atmospheric nitrogen is fixed and assimilated by the symbiont,resulting from the close cooperation between the plant cell and the bacteria.To date,the transcriptome of individual cells isolated from developing soybean nodules has been established,but the transcriptomic signatures of cells from the mature soybean nodule have not yet been characterized.Using single-nucleus RNA-seq and Molecular Cartography technologies,we precisely characterized the transcriptomic signature of soybean root and mature nodule cell types and revealed the co-existence of different sub-populations of B.diazoefficiens-infected cells in the mature soybean nodule,including those actively involved in nitrogen fixation and those engaged in senescence.Mining of the single-cell-resolution nodule transcriptome atlas and the associated gene co-expression network confirmed the role of known nodulation-related genes and identified new genes that control the nodulation process.For instance,we functionally characterized the role of GmFWL3,a plasma membrane microdomain-associated protein that controls rhizobial infection.Our study reveals the unique cellular complexity of the mature soybean nodule and helps redefine the concept of cell types when considering the infection zone of the soybean nodule.展开更多
The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The resu...The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy,scanning electron microscopy and confocal Raman microscopy,have been discussed.The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios.The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation,domain growth anisotropy,and domain–domain interaction have been considered.The formation of variety of self-assembled domain patterns such as fractal-type,finger and web structures,broad domain boundaries,and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal.The possible applications of self-assembling for micro-and nanodomain engineering were reviewed briefly.The review covers mostly the results published by our research group.展开更多
Among the unresolved issues in the study of relaxor ferroelectrics is the role of freezing temperature,across which the dynamics of polarization reversal in relaxor ferroelectrics changes.The presence of this freezing...Among the unresolved issues in the study of relaxor ferroelectrics is the role of freezing temperature,across which the dynamics of polarization reversal in relaxor ferroelectrics changes.The presence of this freezing temperature is best manifested by the appearance of a double polarization hysteresis loop just above the freezing temperature.Given that the polarization pinching evolving into a double hysteresis starts well below the freezing temperature,there exists a transient temperature regime between the nonergodic and the ergodic relaxor states.To clarify the role of the freezing temperature on the pinching,the polarization reversal near the freezing temperature of relaxor(Pb_(1-x)La_(x))(Zr_(1-y)T_(y))_(1-x/4)O_(3)(PLZT)was monitored using three in situ electric field methods:electrocaloric effect,neutron diffraction,and transmission electron microscopy.We demonstrate that the pinching results from a two-step process,1)domain detexturization in the ferroelectric state and 2)miniaturization of domains.This observation explains the recently reported gap between the depolarization temperature T_(d) and the ferroelectric-torelaxor transition temperature T_(F-R) in lead-free relaxors.We further show that T_(d) and T_(F-R),which have long been considered identical in lead-based relaxors,are not the same.The current study suggests that the mismatch between T_(d) and TF-R is an inherent feature in both lead-based and lead-free relaxor ferroelectrics.展开更多
Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been prop...Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.展开更多
Heterovalent doped(K_(0.48-0.07)xNa_(0.52-0.43)xBi_(0.5)x)(Nb_(0.95-0.95x)Sb_(0.05-0.05x)Zrx)O_(3)ceramics were fabricated using conventional solid-state reaction.Then,the phase structures,dielectric,ferroelectric,and...Heterovalent doped(K_(0.48-0.07)xNa_(0.52-0.43)xBi_(0.5)x)(Nb_(0.95-0.95x)Sb_(0.05-0.05x)Zrx)O_(3)ceramics were fabricated using conventional solid-state reaction.Then,the phase structures,dielectric,ferroelectric,and electricstrain properties were investigated.The compositions were tuned to be located at polymorphic phase boundary with increasing heterovalent Bi3t and Zr4t doping levels.A large strain of 0.19%was obtained at relatively low electric fields of 30 kV/cm in the composition of x=0.04.The normalized large-signal d33*values were approximately 633 pm/V under a low driving electric field of 30 kV/cm,which were comparable or larger than the values reported for other lead-free families.The large strains obtained can be attributed to the formation of nanodomains and high-density domain walls,which were confirmed by the observations of domain morphology using transmission electron microscopy(TEM)technique.Excellent temperature stability of the strain properties of the x=0.04 sample could be ascribed to the sluggish behaviour for the local structural heterogeneity in heterovalent-ion doped KNN ceramic.Theoretical simulations revealed that the Zr^(4t)produce the local stress at the BO6 octahedra and Bi3t could yield off-centering of AO12 ployhedron due to the nature of Bi 6s lone pair electrons,which induced lattice expansion and local distortions in the sample.The local displacements are strongly anisotropic in heterovalent-ion doped system.It is believed that random local fields exist in these compositions owing to the eixstence of charge distribution.Such heterovalent doping of Bi^(3t)and Zr^(4t)could destory simultaneously the orthorhombic symmetry and the short-range ferroelecctric order,leading to the formation of complex nanodomains and local structral hetergenenity.Heterovalent doping may,therefore,offer a new avenve to design novel K0.5Na0.5NbO3(KNN)-based materials for their mutifunctional applications.展开更多
基金the China Scholarship Council for financial supportthe Max Planck Society for financial supportOpen Access funding enabled and organized by Projekt DEAL
文摘Sodium-ion capacitors(SICs)have great potential in energy storage due to their low cost,the abundance of Na,and the potential to deliver high energy and power simultaneously.This article demonstrates a template-assisted method to induce graphitic nanodomains and micro-mesopores into nitrogen-doped carbons.This study elucidates that these graphitic nanodomains are beneficial for Na+storage.The obtained N-doped carbon(As8Mg)electrode achieved a reversible capacity of 254 mA h g^(-1)at 0.1 A g^(-1).Moreover,the As8Mg-based SIC device achieves high combinations of power/energy densities(53 W kg^(-1)at 224 Wh kg^(-1)and 10410 W kg^(-1)at 51 Wh kg^(-1))with outstanding cycle stability(99.7%retention over 600 cycles at 0.2 A g^(-1)).Our findings provide insights into optimizing carbon’s microstructure to boost sodium storage in the pseudocapacitive mode.
基金financially supported by the National Key R&D Program of China(No.2021YFB3802800)the Natural Science Foundation of Jiangsu Province(No.BK20200019)+6 种基金the National Natural Science Foundation of China(Nos.52222104,12261160364,51871120,and 51520105001)support from the Guangdong-Hong Kong-Macao Joint Laboratory for Neutron Scattering Science and Technologysupport of the Shenzhen Science and Technology Innovation Committee(No.JCYJ20170413140446951)partial support by the Research Grants Council of the Hong Kong Special Administrative Region,Project N_CityU173/22support of the National Natural Science Foundation of China(No.12275154)the Guangdong Basic and Applied Basic Research Foundation(No.2021B1515140028)supported by the US DOE Office of Science,Office of Basic Energy Sciences.
文摘Fe-based metallic glasses are promising functional materials for advanced magnetism and sensor fields.Tailoring magnetic performance in amorphous materials requires a thorough knowledge of the correlation between structural disorder and magnetic order,which remains ambiguous.Two practical difficulties remain:the first is directly observing subtle magnetic structural changes on multiple scales,and the second is precisely regulating the various amorphous states.Here we propose a novel approach to tailor the amorphous structure through the liquid-liquid phase transition.In-situ synchrotron diffraction has unraveled a medium-range ordering process dominated by edge-sharing cluster connectivity during the liquid-liquid phase transition.Moreover,nanodomains with topological order have been found to exist in composition with liquid-liquid phase transition,manifesting as hexagonal patterns in small-angle neutron scattering profiles.The liquid-liquid phase transition can induce the nanodomains to be more locally ordered,generating stronger exchange interactions due to the reduced Fe–Fe bond length and the enhanced structural order,leading to the increment of saturation magnetization.Furthermore,the increased local heterogeneity at the medium-range scale enhances the magnetic anisotropy,promoting the permeability response under applied stress and leading to a better stress-impedance effect.These experimental results pave the way to tailor the magnetic structure and performance through the liquid-liquid phase transition.
基金Financial support from the National Key Research and Development Program of China(Nos.2020YFB008300,2020YFB008303,and 2020YFB008304)Provincial Natural Science Foundation of Shandong(No.ZR202102220408)+1 种基金National Natural Science Foundation of China(No.51701080)Talent Development Excellent Young Talents Fund Project China(No.20190103053JH).
文摘Conventional kinetics theory for diffusion-controlled phase transformation shows that the reverse transition should lag behind the temperature rise through rapid heating,i.e.,overheating is required.In this work,we found that theβ-transus temperature decreased by∼50℃ during studying theα→βtransformation in Ti-6Al-4V alloy via electropulsing treatment(EPT).The calculation suggests that the acceleration of transformation kinetics cannot be fully explained by Joule heat and athermal effects of the electromigration effect and electron wind theory.The microstructural evolution during EPT was systematically investigated utilizing scanning electron microscope(SEM),electron backscattered diffraction(EBSD),X-ray diffraction(XRD),transmission Kikuchi diffraction(TKD),and transmission electron micro-scope(TEM).Microscopic analysis shows that the nano-sizedωand O'phases formed in theβphase,which causes large numbers of lattice distortion regions.The defects are conducive to accelerating the bulk diffusion of alloying elements inβ.Moreover,the nanodomains limited the growth of martensite,therefore nanocrystalline martensite formed after quenching.These findings develop the understanding of the destructive effect of current on metallic crystal,which will help to guide microstructural regulation in titanium and other alloys.
文摘The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.
基金supported by the National Key Research and De-velopment Program of China(No.2022YFB3800052)the National Natural Science Foundation of China(Nos.12002013,51971009,and 51831006)+1 种基金the Zhejiang Natural Science Foundation(No.LZ23E010004).H.L.Hou also acknowledges the support of the Fundamental Research Funds for the Central Universities(No.501LKQB2020105028)the Opening Fund of the State Key Lab-oratory of Nonlinear Mechanics.
文摘Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been frequently reported in HEAs,however,nanoscale microstructural phase evolution has not been investigated to the same extent.Herein,we have prepared the Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA and investi-gated the strain glass transition and its associated properties using dynamic mechanical analysis and mi-crostructure characterization.We have found that the elastic modulus in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA deviates from Wachtman’s equation and observed the Elinvar effect in the form of temperature-independent mod-ulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 K.The strain glass transition has been evidenced in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy(TEM)cooling,and substantiated by the broken ergodicity during zero-field-cooling/field-cooling.The strain glass transition is believed to account for the Elinvar effect,where the modulus hardening of nano-sized domains compensates dynam-ically with the modulus softening of the transformable matrix.
基金funded by the Nebraska Soybean Board,NSF awards 2127485 and 1854326,and the Nebraska Research Initiative.
文摘The soybean root system is complex.In addition to being composed of various cell types,the soybean root system includes the primary root,the lateral roots,and the nodule,an organ in which mutualistic symbiosis with N-fixing rhizobia occurs.A mature soybean root nodule is characterized by a central infection zone where atmospheric nitrogen is fixed and assimilated by the symbiont,resulting from the close cooperation between the plant cell and the bacteria.To date,the transcriptome of individual cells isolated from developing soybean nodules has been established,but the transcriptomic signatures of cells from the mature soybean nodule have not yet been characterized.Using single-nucleus RNA-seq and Molecular Cartography technologies,we precisely characterized the transcriptomic signature of soybean root and mature nodule cell types and revealed the co-existence of different sub-populations of B.diazoefficiens-infected cells in the mature soybean nodule,including those actively involved in nitrogen fixation and those engaged in senescence.Mining of the single-cell-resolution nodule transcriptome atlas and the associated gene co-expression network confirmed the role of known nodulation-related genes and identified new genes that control the nodulation process.For instance,we functionally characterized the role of GmFWL3,a plasma membrane microdomain-associated protein that controls rhizobial infection.Our study reveals the unique cellular complexity of the mature soybean nodule and helps redefine the concept of cell types when considering the infection zone of the soybean nodule.
基金made possible by Russian Scientific Foundation(Grant 14-12-00826)in part by Ministry of Education and Science of the Russian Federation(UID RFMEFI59414X0011).
文摘The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy,scanning electron microscopy and confocal Raman microscopy,have been discussed.The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios.The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation,domain growth anisotropy,and domain–domain interaction have been considered.The formation of variety of self-assembled domain patterns such as fractal-type,finger and web structures,broad domain boundaries,and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal.The possible applications of self-assembling for micro-and nanodomain engineering were reviewed briefly.The review covers mostly the results published by our research group.
基金the financial support by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2018R1D1A1B07051176)the financial support by the National Science Foundation(NSF)through Grant DMR-1700014the financial support from the ARC Discovery Project Scheme.
文摘Among the unresolved issues in the study of relaxor ferroelectrics is the role of freezing temperature,across which the dynamics of polarization reversal in relaxor ferroelectrics changes.The presence of this freezing temperature is best manifested by the appearance of a double polarization hysteresis loop just above the freezing temperature.Given that the polarization pinching evolving into a double hysteresis starts well below the freezing temperature,there exists a transient temperature regime between the nonergodic and the ergodic relaxor states.To clarify the role of the freezing temperature on the pinching,the polarization reversal near the freezing temperature of relaxor(Pb_(1-x)La_(x))(Zr_(1-y)T_(y))_(1-x/4)O_(3)(PLZT)was monitored using three in situ electric field methods:electrocaloric effect,neutron diffraction,and transmission electron microscopy.We demonstrate that the pinching results from a two-step process,1)domain detexturization in the ferroelectric state and 2)miniaturization of domains.This observation explains the recently reported gap between the depolarization temperature T_(d) and the ferroelectric-torelaxor transition temperature T_(F-R) in lead-free relaxors.We further show that T_(d) and T_(F-R),which have long been considered identical in lead-based relaxors,are not the same.The current study suggests that the mismatch between T_(d) and TF-R is an inherent feature in both lead-based and lead-free relaxor ferroelectrics.
基金supported financially by the National Natural Science Foundation of China (Nos. 51431007, 51831006 and 51771012)
文摘Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.
基金supported by National Science Foundation of China(NSFC No.52172125),the CSS project(YK2015-0602006),the Natural Science Foundation of Shandong Province of China(Grant No.ZR2018BA028),Quzhou Science and Technology Plan Project(2022K108)and General Research Project of Zhejiang Provincial Department of Education(Y202249978).
文摘Heterovalent doped(K_(0.48-0.07)xNa_(0.52-0.43)xBi_(0.5)x)(Nb_(0.95-0.95x)Sb_(0.05-0.05x)Zrx)O_(3)ceramics were fabricated using conventional solid-state reaction.Then,the phase structures,dielectric,ferroelectric,and electricstrain properties were investigated.The compositions were tuned to be located at polymorphic phase boundary with increasing heterovalent Bi3t and Zr4t doping levels.A large strain of 0.19%was obtained at relatively low electric fields of 30 kV/cm in the composition of x=0.04.The normalized large-signal d33*values were approximately 633 pm/V under a low driving electric field of 30 kV/cm,which were comparable or larger than the values reported for other lead-free families.The large strains obtained can be attributed to the formation of nanodomains and high-density domain walls,which were confirmed by the observations of domain morphology using transmission electron microscopy(TEM)technique.Excellent temperature stability of the strain properties of the x=0.04 sample could be ascribed to the sluggish behaviour for the local structural heterogeneity in heterovalent-ion doped KNN ceramic.Theoretical simulations revealed that the Zr^(4t)produce the local stress at the BO6 octahedra and Bi3t could yield off-centering of AO12 ployhedron due to the nature of Bi 6s lone pair electrons,which induced lattice expansion and local distortions in the sample.The local displacements are strongly anisotropic in heterovalent-ion doped system.It is believed that random local fields exist in these compositions owing to the eixstence of charge distribution.Such heterovalent doping of Bi^(3t)and Zr^(4t)could destory simultaneously the orthorhombic symmetry and the short-range ferroelecctric order,leading to the formation of complex nanodomains and local structral hetergenenity.Heterovalent doping may,therefore,offer a new avenve to design novel K0.5Na0.5NbO3(KNN)-based materials for their mutifunctional applications.
