Due to ever-increasing concerns about safety issues in using Li ionic batteries,solid electrolytes have extensively explored.The Li-rich antiperovskite Li_(3)OBr has been considered as a promising solid electrolyte ca...Due to ever-increasing concerns about safety issues in using Li ionic batteries,solid electrolytes have extensively explored.The Li-rich antiperovskite Li_(3)OBr has been considered as a promising solid electrolyte candidate,but it still suffers challenges to achieve a high ionic conductivity owing to the high intrinsic symmetry of the crystal lattice.Herein,we presented a design strategy that introduces various point defects and grain boundaries to break the high lattice symmetry of Li_(3)OBr crystal,and their effect and microscopic mechanism of promoting the migration of Li-ion were explored theoretically.It has been found that Li_(i)are the dominant defects responsible for the fast Li-ion diffusion in bulk Li_(3)OBr and its surface,but they are easily trapped by the grain boundaries,leading to the annihilating of the Frenkel defect pair V'_(Li)+Li_(i),and thus limits the V'_(Li)diffusion at the grain boundaries.The V_(Br)defect near the grain boundaries can effectively drive V'_(Li)across the grain boundary,thereby converting the carrier of Li^(+)migration from Li,in the bulk and surface to V'_(Li)at the grain boundary,and thus improving the ionic conductivity in the whole Li_(3)OBr crystal.This work provides a comprehensive insight into the Li^(+)transport and conduction mechanism in the Li_(3)OBr electrolyte.It opens a new way of improving the conductivity for all-solid-state Li electrolyte material through the defect design.展开更多
Driven by safety issues,environmental concerns,and high costs,rechargeable aqueous zinc-ion batteries(ZIBs)have received increasing attention in recent years owing to their unique advantages.However,the sluggish kinet...Driven by safety issues,environmental concerns,and high costs,rechargeable aqueous zinc-ion batteries(ZIBs)have received increasing attention in recent years owing to their unique advantages.However,the sluggish kinetics of divalent charge Zn^(2+)in the cathode materials caused by the strong electrostatic interaction and their unsatisfactory cycle life hinder the development of ZIBs.Herein,organic cations and Zn^(2+)ions co-pre-inserted vanadium oxide([N(CH_(3))_(4)]_(0.77),Zn_(0.23))V_(8)O_(20)·3.8H_(2)O are reported as the cathode for ultra-stable aqueous ZIBs,in which the weaker electrostatic interactions between Zn^(2+)and organic ion-pinned vanadium oxide can induce the high reversibility of Zn^(2+)insertion and extraction,thereby improving the cycle life.It is demonstrated that([N(CH_(3))_(4)]_(0.77),Zn_(0.23))V_(8)O_(20)·3.8H_(2)O cathodes deliver a discharge capacity of 181 mA h g^(-1)at8 A g^(-1)and ultra-long life span(99.5%capacity retention after 2000 cycles).A reversible Zn^(2+)/H^(+)ions(de)intercalation storage process and pseudocapacitive charge storage are characterized.The weaker interactions between organic ion and Zn^(2+)open a novel avenue for the design of highly reversible cathode materials with long-term cycling stability.展开更多
The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devic...The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devices.Achieving efficient anomalous valley Hall effect(AVHE)switching in antiferrovalley materials constitutes an important step towards their application,yet such advancement has been scarcely reported so far.In this study,we demonstrate,through first-principles calculations and model analysis,that the experimentally synthesized MnSe monolayer is a hitherto unexplored but exceptional antiferrovalley material with spontaneous valley polarization.And more importantly,by constructing a multiferroic MnSe/In_(2)Se_(3) heterostructure,the desired nonvolatile on/off switching of the AVHE can be successfully realized through polarization reversal.This unique phenomenon,characterized by the emergence/annihilation of fully spin-polarized valley polarization,arises from the combined effect of strong magnetoelectric coupling-induced changes in magnetic anisotropy and PT symmetry breaking.Our findings provide a novel approach for achieving nonvolatile control of the AVHE in antiferrovalley materials,opening up significant opportunities for valleytronic applications.展开更多
Enhancing the stability of piezoelectric properties is essential for ensuring the reliability of high-temperature piezoelectric sensors.In this study,we have synthesized AlN piezoelectric crystals as representative ma...Enhancing the stability of piezoelectric properties is essential for ensuring the reliability of high-temperature piezoelectric sensors.In this study,we have synthesized AlN piezoelectric crystals as representative materials and employed first-principles methods to investigate their temperature-dependent piezoelectric properties.By integrating the effects of lattice expansion and electron–phonon interactions,we accurately constructed the crystal structure of AlN across a wide temperature range and successfully predicted its piezoelectric behavior.Theoretical analysis reveals that ion polarization driven by lattice distortion and elastic softening of chemical bonds maintains the overall structural integrity of defect-free AlN single crystals,resulting in a stable piezoelectric coefficient d33 with a deviation of only 8.55%at temperatures up to 1300 K.However,experimental results indicate that the stability of the piezoelectric performance of the grown AlN crystals is disrupted at temperatures above 870 K.This temperature limitation is attributed to point defects within AlN crystals,particularly those caused by oxygen-substituted nitrogen(ON).These findings provide valuable guidance for enhancing the piezoelectric temperature stability of AlN crystals through optimized experimental conditions,such as oxygen atmosphere treatment and defect modification during crystal growth.展开更多
Herein,the core-shell structured N-doped carbon coated Fe7S8 nano-aggregates(Fe7S8@NC)were controllably prepared via a simple three-step synthesis strategy.The appropriate thickness of N-doped carbon layer outside Fe7...Herein,the core-shell structured N-doped carbon coated Fe7S8 nano-aggregates(Fe7S8@NC)were controllably prepared via a simple three-step synthesis strategy.The appropriate thickness of N-doped carbon layer outside Fe7S8 nano-aggregates can not only inhibit the particle pulverization induced by the big volume changes of Fe7S8,but can increase the electron transfer efficiency.The hierarchical Fe7S8 nano-aggregates composed of some primary nanoparticles can accelerate the lithium or sodium diffusion kinetics.As anode materials for Li-ion batteries(LIBs),the well-designed Fe7S8@NC nanocomposites exhibit outstanding lithium storage performance,which is better than that of pure Fe7S8,Fe3O4@NC and Fe7S8@C.Among these nanocomposites,the N-doped carbon coated Fe7S8 with carbon content of 26.87 wt.%shows a high reversible specific capacity of 833 mAh·g^−1 after 1,000 cycles at a high current density of 2 A·g^−1.The above electrode also shows excellent high rate sodium storage performance.The experimental and theoretical analyses indicate that the outstanding electrochemical performance could be attributed to the synergistic effect of hierarchical Fe7S8 nanostructure and conductive N-doped carbon layer.The quantitative kinetic analysis indicates that the charge storage of Fe7S8@NC electrode is a combination of diffusion-controlled battery behavior and surface-induced capacitance behavior.展开更多
Two-dimensional(2D)XY ferromagnets have drawn pronounced interest in recent years,but the characteristic of easy-plane magnetization restricts their application in spintronics to some extent.Here,we propose a general ...Two-dimensional(2D)XY ferromagnets have drawn pronounced interest in recent years,but the characteristic of easy-plane magnetization restricts their application in spintronics to some extent.Here,we propose a general strategy for constructing multiferroic van der Waals heterostructures,aiming to achieve electrical control over the magnetic anisotropy in 2D XY ferromagnets.The validity of this strategy is verified by the heterostructure composed of ferromagnetic VBi_(2)Te_(4) and ferroelectric In_(2)Se_(3) monolayers.By manipulating the polarized states of In_(2)Se_(3),the VBi_(2)Te_(4) can be reversibly transformed between 2D XY and Heisenberg ferromagnets,characterized by the switching of easy magnetization axis between in-plane and out-of-plane directions.More interestingly,accompanied by the changes in magnetic anisotropy,the VBi_(2)Te_(4) also demonstrates a phase transition from a semiconductor to a half-metal state,which can be ascribed to the band alignment and interfacial charge transfer.The switchable magnetic and electronic properties enable the heterostructure to be utilized in nonvolatile memory and logic devices.Additionally,the half-metallicity and magnetocrystalline anisotropy energy of the heterostructure can be effectively tuned by biaxial strain.These findings not only pave the way for electrically nonvolatile control of 2D XY ferromagnet,but also facilitate the development of interfacial magnetoelectric physics and applications.展开更多
Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application.Here,by constructing van der Waals heterostructures composed of two-dimensi...Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application.Here,by constructing van der Waals heterostructures composed of two-dimensional(2D)A-type antiferromagnetic NiI_(2)bilayer(bi-NiI_(2))and ferroelectric In_(2)Se_(3)with different thickness,we propose that the half-metallicity is realizable and switchable in the bi-NiI_(2)proximate to In_(2)Se_(3)bilayer(bi-In_(2)Se_(3)).The polarization flipping of the bi-In_(2)Se_(3)successfully drives transition between half-metal and semiconductor for the bi-NiI_(2).This intriguing phenomenon is attributed to the joint effect of polarization field-induced energy band shift and interfacial charge transfer.Besides,the easy magnetization axis of the bi-NiI_(2)is also dependent on the polarization direction of the bi-In_(2)Se_(3).The half-metallicity and magnetic anisotropy energy of the bi-NiI_(2)in heterostructure can be effectively manipulated by strain.These findings provide not only a feasible strategy to achieve and control half-metallicity in 2D antiferromagnets,but also a promising candidate to design advanced nanodevices.展开更多
Studies have reported that Mo-doped LiNbO_(3) exhibits excellent photorefractive performance,which may be attributed to the Mo abnormally occupation in Nb sites(MoNb)and the MoNb photorefractive centres.Therefore,we i...Studies have reported that Mo-doped LiNbO_(3) exhibits excellent photorefractive performance,which may be attributed to the Mo abnormally occupation in Nb sites(MoNb)and the MoNb photorefractive centres.Therefore,we investigate the basic characteristics of Mo-doped LiNbO_(3),including the preferable substitutional sites,doping stability,lattice relaxation,and electronic structures using the spin-polarised density functional theory within semi-local and hybrid functionals.Particularly,the type and properties of the polarons in Mo-doped LiNbO_(3) are studied intensively,and the advantages of MoNb polarons with respect to the MoLi polarons are highlighted.The calculation results of both transfer energies and defect formation energies show that MoNb are preferable to be formed in both stoichiometric and congruent LiNbO_(3),while Mo substitutional Li(MoLi)is consumed in small amounts.MoNb could act as small bound polarons that exhibit fast response to light with respect to the MoLi bound bipolarons.The introduced double-centre by Mo doping is partly responsible for the excellent photorefractive properties of Mo-doped LiNbO_(3).展开更多
The Zintl compound EuMg_(2)Sb_(2)is a promising thermoelectric material due to its inherently low lattice thermal conductivity and tunable electronic and thermal properties related to its multi-component nature.Howeve...The Zintl compound EuMg_(2)Sb_(2)is a promising thermoelectric material due to its inherently low lattice thermal conductivity and tunable electronic and thermal properties related to its multi-component nature.However,the large difference in electronegativity between Mg and Sb results in poor electronic transport properties,reducing its thermoelectric conversion efficiency and limiting its practical application.Thus,this study investigates a doping modification strategy for enhancing the thermoelectric performance of EuMg_(2)Sb_(2)and the microscopic mechanism using thefirst-principle calculations combined with the Boltzmann transport theory.Indeed,the larger energy separation at the valence band maximum is the key factor affecting the electronic transport properties of EuMg_(2)Sb_(2).The results demonstrate that Zn doping at the Mg site effectively increases the thermoelectric performance by promoting the valence band convergence owing to the close electronegativity to Sb and softening the phonon thus largely suppressing the lattice thermal conductivity.By optimizing the Zn doping concentration,the highestfigure of merit(zT)value is significantly increased to 2.24(2.66)in the x(z)direction at 800 K.The results suggest that the proposed modulation strategy and effect are of great significance for improving the thermoelectric performance of Zintl materials.展开更多
The yttrium calcium oxyborate crystal(YCa_(4)O(BO_(3))_(3),YCOB)has been actively studied for hightemperature piezoelectric sensing applications.In this work,the stability of electric properties of YCOB crystal anneal...The yttrium calcium oxyborate crystal(YCa_(4)O(BO_(3))_(3),YCOB)has been actively studied for hightemperature piezoelectric sensing applications.In this work,the stability of electric properties of YCOB crystal annealed in critical conditions(high-temperatures of 900-1100℃ with a low oxygen partial pressure of 4×10^(-6) atm for 24 h)was investigated and the recovery mechanism for the electrical resisitivity,dielectric permittivity and dielectric loss were studied,taking advantage of the X-ray photoelectron spectra and the first principle calculations.The electrical resistivity of the annealed YCOB crystal was slightly decreased when compared to the pristine counterpart,being(2-5)×10^(7) Ω·cm at 850C.The dielectric permittivity and dielectric loss were found to increase after annealing,showing recoverable behaviours after thermal treatment above 650℃ in air.The calculated vacancy formation energy indicates that the oxygen vacancy is the dominant defects in YCOB.The formation of oxygen vacancy weakens the chemical bonding strength between B(Ca or Y)and O atoms,introduces extra donor levels in the band gap,which excites the electrons to conduction band more easily thus enhances the electrical conductivity and dielectric loss.The recovered electrical properties are believed to be associated with the reduced vacancy defects at elevated temperatures in air.展开更多
Ti-based anode materials in sodium ion batteries have attracted extensive interests due to its abundant resources,low toxicity,easy synthesis and long cycle life.However,low Coulombic efficiency and limited specific c...Ti-based anode materials in sodium ion batteries have attracted extensive interests due to its abundant resources,low toxicity,easy synthesis and long cycle life.However,low Coulombic efficiency and limited specific capacity affect their applications.Here,cubic-phase TiP_(2)O_(7)is examined as anode materials,using in-situ/ex-situ characterization techniques.It is concluded that the redox reactions of Ti4^(+)/Ti^(3+)and Ti^(3+)/Ti^(0)consecutively occur during the discharge/charge processes,both of which are highly reversible.These reactions make the specific capacity of TiP_(2)O_(7)even higher than the case of TiO2 that only contains a simple anion,0^(2-).Interestingly,Ti species participate only one of the redox reactions,due to the remarkable difference in local structures related to the sodiation process.The stable discharge/charge products in TiP_(2)O_(7)reduce the side reactions and improve the Coulombic efficiency as compared to T i02.These features make it a promising Ti-based anode for sodium ion batteries.Therefore,TiP_(2)O_(7)@C microflowers exhibit excellent electrochemical performances,〜109 mAh·g^(-1)after 10,000 cycles at 2 A·g^(-1),or 95.2 mAh·g^(-1)at 10 A·g^(-1).The results demonstrate new opportunities for advanced Ti-based anodes in sodium ion batteries.展开更多
基金supported by grants from the National Science Foundation of Shandong Province(no.ZR2020ZD35)the Young Talent Cultivation Program of the State Key Laboratory of Crystal Materials,Shandong University
文摘Due to ever-increasing concerns about safety issues in using Li ionic batteries,solid electrolytes have extensively explored.The Li-rich antiperovskite Li_(3)OBr has been considered as a promising solid electrolyte candidate,but it still suffers challenges to achieve a high ionic conductivity owing to the high intrinsic symmetry of the crystal lattice.Herein,we presented a design strategy that introduces various point defects and grain boundaries to break the high lattice symmetry of Li_(3)OBr crystal,and their effect and microscopic mechanism of promoting the migration of Li-ion were explored theoretically.It has been found that Li_(i)are the dominant defects responsible for the fast Li-ion diffusion in bulk Li_(3)OBr and its surface,but they are easily trapped by the grain boundaries,leading to the annihilating of the Frenkel defect pair V'_(Li)+Li_(i),and thus limits the V'_(Li)diffusion at the grain boundaries.The V_(Br)defect near the grain boundaries can effectively drive V'_(Li)across the grain boundary,thereby converting the carrier of Li^(+)migration from Li,in the bulk and surface to V'_(Li)at the grain boundary,and thus improving the ionic conductivity in the whole Li_(3)OBr crystal.This work provides a comprehensive insight into the Li^(+)transport and conduction mechanism in the Li_(3)OBr electrolyte.It opens a new way of improving the conductivity for all-solid-state Li electrolyte material through the defect design.
基金supported by the funding from the National Natural Science Foundation of China(grant nos.51902187,52072224,and 51732007)the Natural Science Foundation of Shandong Province(ZR2018BEM010)+3 种基金the Science Fund for Distinguished Young Scholars of Shandong Province(ZR2019JQ16)the Fundamental Research Funds of Shandong UniversityYoung Elite Scientist Sponsorship Program by CAST(YESS)the support from Collaborative Innovation Center of Technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong
文摘Driven by safety issues,environmental concerns,and high costs,rechargeable aqueous zinc-ion batteries(ZIBs)have received increasing attention in recent years owing to their unique advantages.However,the sluggish kinetics of divalent charge Zn^(2+)in the cathode materials caused by the strong electrostatic interaction and their unsatisfactory cycle life hinder the development of ZIBs.Herein,organic cations and Zn^(2+)ions co-pre-inserted vanadium oxide([N(CH_(3))_(4)]_(0.77),Zn_(0.23))V_(8)O_(20)·3.8H_(2)O are reported as the cathode for ultra-stable aqueous ZIBs,in which the weaker electrostatic interactions between Zn^(2+)and organic ion-pinned vanadium oxide can induce the high reversibility of Zn^(2+)insertion and extraction,thereby improving the cycle life.It is demonstrated that([N(CH_(3))_(4)]_(0.77),Zn_(0.23))V_(8)O_(20)·3.8H_(2)O cathodes deliver a discharge capacity of 181 mA h g^(-1)at8 A g^(-1)and ultra-long life span(99.5%capacity retention after 2000 cycles).A reversible Zn^(2+)/H^(+)ions(de)intercalation storage process and pseudocapacitive charge storage are characterized.The weaker interactions between organic ion and Zn^(2+)open a novel avenue for the design of highly reversible cathode materials with long-term cycling stability.
基金supported by the National Natural Science Foundation of China(Grant No.12004137)the Taishan Scholar Program of Shandong Province(Grant No.ts20190939)+1 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA052)the Qilu Young Scholar of Shandong University.
文摘The exploration of two-dimensional antiferrovalley materials as potential candidates for valleytronics offers intriguing prospects to investigate exotic valley physics and develop next-generation nano-electronic devices.Achieving efficient anomalous valley Hall effect(AVHE)switching in antiferrovalley materials constitutes an important step towards their application,yet such advancement has been scarcely reported so far.In this study,we demonstrate,through first-principles calculations and model analysis,that the experimentally synthesized MnSe monolayer is a hitherto unexplored but exceptional antiferrovalley material with spontaneous valley polarization.And more importantly,by constructing a multiferroic MnSe/In_(2)Se_(3) heterostructure,the desired nonvolatile on/off switching of the AVHE can be successfully realized through polarization reversal.This unique phenomenon,characterized by the emergence/annihilation of fully spin-polarized valley polarization,arises from the combined effect of strong magnetoelectric coupling-induced changes in magnetic anisotropy and PT symmetry breaking.Our findings provide a novel approach for achieving nonvolatile control of the AVHE in antiferrovalley materials,opening up significant opportunities for valleytronic applications.
基金supported by the“National Key R&D Program of China”,the National Science Foundation of China(Grant No.22209201)Natural Science Foundation of Shandong Province(ZR2022QF044)Future Plans of Young Scholars at Shandong University.
文摘Enhancing the stability of piezoelectric properties is essential for ensuring the reliability of high-temperature piezoelectric sensors.In this study,we have synthesized AlN piezoelectric crystals as representative materials and employed first-principles methods to investigate their temperature-dependent piezoelectric properties.By integrating the effects of lattice expansion and electron–phonon interactions,we accurately constructed the crystal structure of AlN across a wide temperature range and successfully predicted its piezoelectric behavior.Theoretical analysis reveals that ion polarization driven by lattice distortion and elastic softening of chemical bonds maintains the overall structural integrity of defect-free AlN single crystals,resulting in a stable piezoelectric coefficient d33 with a deviation of only 8.55%at temperatures up to 1300 K.However,experimental results indicate that the stability of the piezoelectric performance of the grown AlN crystals is disrupted at temperatures above 870 K.This temperature limitation is attributed to point defects within AlN crystals,particularly those caused by oxygen-substituted nitrogen(ON).These findings provide valuable guidance for enhancing the piezoelectric temperature stability of AlN crystals through optimized experimental conditions,such as oxygen atmosphere treatment and defect modification during crystal growth.
基金the National Natural Science Foundation of China(No.51772257)the Major Basic Research Project of Shandong Natural Science Foundation(No.ZR2018ZC1459)Doctor Foundation of Shandong Province(No.ZR2017BB081)for financial support.
文摘Herein,the core-shell structured N-doped carbon coated Fe7S8 nano-aggregates(Fe7S8@NC)were controllably prepared via a simple three-step synthesis strategy.The appropriate thickness of N-doped carbon layer outside Fe7S8 nano-aggregates can not only inhibit the particle pulverization induced by the big volume changes of Fe7S8,but can increase the electron transfer efficiency.The hierarchical Fe7S8 nano-aggregates composed of some primary nanoparticles can accelerate the lithium or sodium diffusion kinetics.As anode materials for Li-ion batteries(LIBs),the well-designed Fe7S8@NC nanocomposites exhibit outstanding lithium storage performance,which is better than that of pure Fe7S8,Fe3O4@NC and Fe7S8@C.Among these nanocomposites,the N-doped carbon coated Fe7S8 with carbon content of 26.87 wt.%shows a high reversible specific capacity of 833 mAh·g^−1 after 1,000 cycles at a high current density of 2 A·g^−1.The above electrode also shows excellent high rate sodium storage performance.The experimental and theoretical analyses indicate that the outstanding electrochemical performance could be attributed to the synergistic effect of hierarchical Fe7S8 nanostructure and conductive N-doped carbon layer.The quantitative kinetic analysis indicates that the charge storage of Fe7S8@NC electrode is a combination of diffusion-controlled battery behavior and surface-induced capacitance behavior.
基金supported by the National Natural Science Foundation of China(Grant No.12004137)the Taishan Scholar Program of Shandong Province(Grant No.ts20190939)+1 种基金the Natural Science Foundation of Shandong Province(Grant Nos.ZR2020QA052 and ZR2020ZD35)the Young Scholars Program of Shandong University(No.2018WLJH65).
文摘Two-dimensional(2D)XY ferromagnets have drawn pronounced interest in recent years,but the characteristic of easy-plane magnetization restricts their application in spintronics to some extent.Here,we propose a general strategy for constructing multiferroic van der Waals heterostructures,aiming to achieve electrical control over the magnetic anisotropy in 2D XY ferromagnets.The validity of this strategy is verified by the heterostructure composed of ferromagnetic VBi_(2)Te_(4) and ferroelectric In_(2)Se_(3) monolayers.By manipulating the polarized states of In_(2)Se_(3),the VBi_(2)Te_(4) can be reversibly transformed between 2D XY and Heisenberg ferromagnets,characterized by the switching of easy magnetization axis between in-plane and out-of-plane directions.More interestingly,accompanied by the changes in magnetic anisotropy,the VBi_(2)Te_(4) also demonstrates a phase transition from a semiconductor to a half-metal state,which can be ascribed to the band alignment and interfacial charge transfer.The switchable magnetic and electronic properties enable the heterostructure to be utilized in nonvolatile memory and logic devices.Additionally,the half-metallicity and magnetocrystalline anisotropy energy of the heterostructure can be effectively tuned by biaxial strain.These findings not only pave the way for electrically nonvolatile control of 2D XY ferromagnet,but also facilitate the development of interfacial magnetoelectric physics and applications.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12004137 and 11974145)the Key Research and Development Program of Shandong Province(No.2019JZZY010313)Natural Science Foundation of Shandong Province(Grant Nos.ZR2020QA052 and ZR2020ZD28).
文摘Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application.Here,by constructing van der Waals heterostructures composed of two-dimensional(2D)A-type antiferromagnetic NiI_(2)bilayer(bi-NiI_(2))and ferroelectric In_(2)Se_(3)with different thickness,we propose that the half-metallicity is realizable and switchable in the bi-NiI_(2)proximate to In_(2)Se_(3)bilayer(bi-In_(2)Se_(3)).The polarization flipping of the bi-In_(2)Se_(3)successfully drives transition between half-metal and semiconductor for the bi-NiI_(2).This intriguing phenomenon is attributed to the joint effect of polarization field-induced energy band shift and interfacial charge transfer.Besides,the easy magnetization axis of the bi-NiI_(2)is also dependent on the polarization direction of the bi-In_(2)Se_(3).The half-metallicity and magnetic anisotropy energy of the bi-NiI_(2)in heterostructure can be effectively manipulated by strain.These findings provide not only a feasible strategy to achieve and control half-metallicity in 2D antiferromagnets,but also a promising candidate to design advanced nanodevices.
基金National Supercomputer Center in Tianjin,and the calculations were performed on TianHe-1(A)financial support from the National Natural Science Foundation of China(No.51502158).
文摘Studies have reported that Mo-doped LiNbO_(3) exhibits excellent photorefractive performance,which may be attributed to the Mo abnormally occupation in Nb sites(MoNb)and the MoNb photorefractive centres.Therefore,we investigate the basic characteristics of Mo-doped LiNbO_(3),including the preferable substitutional sites,doping stability,lattice relaxation,and electronic structures using the spin-polarised density functional theory within semi-local and hybrid functionals.Particularly,the type and properties of the polarons in Mo-doped LiNbO_(3) are studied intensively,and the advantages of MoNb polarons with respect to the MoLi polarons are highlighted.The calculation results of both transfer energies and defect formation energies show that MoNb are preferable to be formed in both stoichiometric and congruent LiNbO_(3),while Mo substitutional Li(MoLi)is consumed in small amounts.MoNb could act as small bound polarons that exhibit fast response to light with respect to the MoLi bound bipolarons.The introduced double-centre by Mo doping is partly responsible for the excellent photorefractive properties of Mo-doped LiNbO_(3).
基金the National Supercomputer Center in Tianjin,and the calculations were performed on TianHe-1(A).It was supported by grants from the General Program of National Natural Science Foundation of China(No.52372007)the General Q.Song,L.Bai,X.Gao et al.Journal of Materiomics 11(2025)1009107Program of Natural Science Foundation of Shandong Province(No.ZR2023ME125)+1 种基金the Taishan Industry Leading Talents Program(No.tscx202312007)Qilu Young Scholars Program of Shandong University.
文摘The Zintl compound EuMg_(2)Sb_(2)is a promising thermoelectric material due to its inherently low lattice thermal conductivity and tunable electronic and thermal properties related to its multi-component nature.However,the large difference in electronegativity between Mg and Sb results in poor electronic transport properties,reducing its thermoelectric conversion efficiency and limiting its practical application.Thus,this study investigates a doping modification strategy for enhancing the thermoelectric performance of EuMg_(2)Sb_(2)and the microscopic mechanism using thefirst-principle calculations combined with the Boltzmann transport theory.Indeed,the larger energy separation at the valence band maximum is the key factor affecting the electronic transport properties of EuMg_(2)Sb_(2).The results demonstrate that Zn doping at the Mg site effectively increases the thermoelectric performance by promoting the valence band convergence owing to the close electronegativity to Sb and softening the phonon thus largely suppressing the lattice thermal conductivity.By optimizing the Zn doping concentration,the highestfigure of merit(zT)value is significantly increased to 2.24(2.66)in the x(z)direction at 800 K.The results suggest that the proposed modulation strategy and effect are of great significance for improving the thermoelectric performance of Zintl materials.
基金financially supported by the Primary Research&Development Plan of Shandong Province(2017CXGC0413)the National Natural Science Foundation of China(51872165).
文摘The yttrium calcium oxyborate crystal(YCa_(4)O(BO_(3))_(3),YCOB)has been actively studied for hightemperature piezoelectric sensing applications.In this work,the stability of electric properties of YCOB crystal annealed in critical conditions(high-temperatures of 900-1100℃ with a low oxygen partial pressure of 4×10^(-6) atm for 24 h)was investigated and the recovery mechanism for the electrical resisitivity,dielectric permittivity and dielectric loss were studied,taking advantage of the X-ray photoelectron spectra and the first principle calculations.The electrical resistivity of the annealed YCOB crystal was slightly decreased when compared to the pristine counterpart,being(2-5)×10^(7) Ω·cm at 850C.The dielectric permittivity and dielectric loss were found to increase after annealing,showing recoverable behaviours after thermal treatment above 650℃ in air.The calculated vacancy formation energy indicates that the oxygen vacancy is the dominant defects in YCOB.The formation of oxygen vacancy weakens the chemical bonding strength between B(Ca or Y)and O atoms,introduces extra donor levels in the band gap,which excites the electrons to conduction band more easily thus enhances the electrical conductivity and dielectric loss.The recovered electrical properties are believed to be associated with the reduced vacancy defects at elevated temperatures in air.
基金the National Natural Science Foundation of China(Nos.21971146,61527809,21471090)Development Programs of Shandong Province(Nos.2017 GGX40101,2017CXGC0503)+2 种基金Taishan Scholarship of Shandong Province(No.ts201511004)the Science,Technology and Innovation Commission of Shenzhen Municipality(No.JCYJ20180305164424922)the Fundamental Research Funds of Shandong University(No.2018JC023).We thank Dr.Kepeng Song for high-resolution transmission electron microscope images and thank Dr.Tania Silver for helpful discussions.
文摘Ti-based anode materials in sodium ion batteries have attracted extensive interests due to its abundant resources,low toxicity,easy synthesis and long cycle life.However,low Coulombic efficiency and limited specific capacity affect their applications.Here,cubic-phase TiP_(2)O_(7)is examined as anode materials,using in-situ/ex-situ characterization techniques.It is concluded that the redox reactions of Ti4^(+)/Ti^(3+)and Ti^(3+)/Ti^(0)consecutively occur during the discharge/charge processes,both of which are highly reversible.These reactions make the specific capacity of TiP_(2)O_(7)even higher than the case of TiO2 that only contains a simple anion,0^(2-).Interestingly,Ti species participate only one of the redox reactions,due to the remarkable difference in local structures related to the sodiation process.The stable discharge/charge products in TiP_(2)O_(7)reduce the side reactions and improve the Coulombic efficiency as compared to T i02.These features make it a promising Ti-based anode for sodium ion batteries.Therefore,TiP_(2)O_(7)@C microflowers exhibit excellent electrochemical performances,〜109 mAh·g^(-1)after 10,000 cycles at 2 A·g^(-1),or 95.2 mAh·g^(-1)at 10 A·g^(-1).The results demonstrate new opportunities for advanced Ti-based anodes in sodium ion batteries.
