Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal ...Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance.Herein,the thermoelectric properties of nominal Bi_(1-x)Cu_(x)Se samples were studied as the functions of the content of Cu additive and temperature.It is found that Cu additives in BiSe(1)profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process,(2)increase considerably the effective mass and thus the Seebeck coefficient,and(3)yield point defects and Cu-Se secondary phases that effectively scatter heat-carrying phonons.As a result,the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT~0.29 in Bi_(1-x)Cu_(x)Se(x=0.03)sample at 467 K in parallel to the pressure direction and a zT~0.20 at 468 K in the perpendicular direction.展开更多
The commercial viability of thermoelectric(TE)devices relies heavily on two factors:cost reduction and efficiency enhancement.In this study,we first produce p-type Cu_(12)Sb_(4)S_(16-x)(x=0,3,4)using a low-temperature...The commercial viability of thermoelectric(TE)devices relies heavily on two factors:cost reduction and efficiency enhancement.In this study,we first produce p-type Cu_(12)Sb_(4)S_(16-x)(x=0,3,4)using a low-temperature bottom-up approach and demonstrate Cu_(12)Sb_(4)S_(13)to show the best TE performance among the three tested compositions.Subsequently,the TE energy conversion efficiency of Cu_(12)Sb_(4)S_(13)is further enhanced by optimizing its electronic band structure through the incorporation of small amounts of tel-lurium.At an optimal Te content of 5 mol%,more than a twofold increase in the TE figure of merit(zT)is obtained.To gain insight into the mechanism of improvement on the transport properties of the mate-rial,we compare the interphase transport mechanism by incorporating nanodomains of different metals(Ag and Cu)into the Cu_(12)Sb_(4)S_(13)matrix.The improved electrical conductivity obtained with Cu_(12)Sb_(4)S_(13)-Te nanocomposites is attributed to a charge flooding of the Cu_(12)Sb_(4)S_(13)surface.In contrast,excessive down-ward band-bending at the interphases of Ag/Cu metal-semiconductor drastically reduces the electrical conductivity.Besides,a weighted mobility(μw)analysis shows a dominant thermal activation of carri-ers in Cu_(12)Sb_(4)S_(13)-Te nanocomposites.In this material,a strong decrease in lattice thermal conductivity is also found,which is associated with a phonon-carrier scattering mechanism.Our work shows the impor-tance of proper band-engineering in TE nanocomposites to decouple electrical and thermal transport to enhance TE performance,and the efficacy ofμw for electrical and thermal transport analysis.展开更多
Recently,off-centering behavior has been discovered in a series of thermoelectric materials.This behavior indicates that the constituent atoms of the lattice displace from their coordination centers,leading to the loc...Recently,off-centering behavior has been discovered in a series of thermoelectric materials.This behavior indicates that the constituent atoms of the lattice displace from their coordination centers,leading to the locally distorted state and local symmetry breaking,while the material still retains its original crystallographic symmetry.This effect has been proved to be the root cause of ultralow thermal conductivity in off-centering materials,and is considered as an effective tool to regulate the thermal conductivity and improve the thermoelectric performance.Herein,we present a collection of recently discovered off-centering compounds,discuss their electronic origins and local coordination structures,and illuminate the underlying mechanism of the off-centering effect on phonon transport and thermal conductivity.This paper presents a comprehensive view of our current understanding to the off-centering effect,and provides a new idea for designing high performance thermoelectrics.展开更多
Phonon bandgap typically has a significant effect on phonon-phonon scattering process.In this work,the effects of mass modified phonon bandgap inθ-phase Ta N are systemically investigated by the means of first-princi...Phonon bandgap typically has a significant effect on phonon-phonon scattering process.In this work,the effects of mass modified phonon bandgap inθ-phase Ta N are systemically investigated by the means of first-principles calculations with linearized Boltzmann transport equation.Through detailed calculations,we find that phonon bandgap has a significant effect on three-phonon process while exhibits a much weaker effect on four-phonon process.The reason for the ultrahigh thermal conductivity ofθ-phase Ta N is the long lifetime of phonons including both three-phonon and four-phonon processes,which originates from the weak phonon anharmonicity and large phonon bandgap-induced small phonon-phonon scattering phase space.This work advances the understanding of phonon bandgap effects on phonon transport.展开更多
Two dimensional excitonic devices are of great potential to overcome the dilemma of response time and integration in current generation of electron or/and photon based systems.The ultrashort diffusion length of excito...Two dimensional excitonic devices are of great potential to overcome the dilemma of response time and integration in current generation of electron or/and photon based systems.The ultrashort diffusion length of exciton arising from ultrafast relaxation and low carrier mobility greatly discounts the performance of excitonic devices.Phonon scattering and exciton localization are crucial to understand the modulation of exciton flux in two dimensional disorder energy landscape,which still remain elusive.Here,we report an optimized scheme for exciton diffusion and relaxation dominated by phonon scattering and disorder potentials in WSe2 monolayers.The effective diffusion coefficient is enhanced by>200%at 280 K.The excitons tend to be localized by disorder potentials accompanied by the steadily weakening of phonon scattering when temperature drops to 260 K,and the onset of exciton localization brings forward as decreasing temperature.These findings identify that phonon scattering and disorder potentials are of great importance for long-range exciton diffusion and thermal management in exciton based systems,and lay a firm foundation for the development of functional excitonic devices.展开更多
SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectr...SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectric transport parameters to achieve high thermoelectric properties of p-type SiGe in the mid-temperature region by incorporating nano-TaC into SiGe combined ball milling with spark plasma sintering.By optimizing the amount of TaC in the SiGe matrix,the power factors were significantly increased due to the modulation doping effect based on the work function matching of SiGe with TaC.Simultaneously,the ensemble effect of the nanostructure leads to a significant decrease in thermal conductivity.Thus,a high ZT of 1.06 was accomplished at 873 K,which is 64%higher than that of typical radioisotope thermoelectric generator.Our research offers a novel strategy for expanding and enhancing the thermoelectric properties of SiGe materials in the medium temperature range.展开更多
It is common sense that a phase interface(or grain boundary)could be used to scatter phonons in thermoelectric(TE)materials,resulting in low thermal conductivity(k).However,a large number of impurity phases are always...It is common sense that a phase interface(or grain boundary)could be used to scatter phonons in thermoelectric(TE)materials,resulting in low thermal conductivity(k).However,a large number of impurity phases are always so harmful to the transport of carriers that poor TE performance is obtained.Here,we demonstrate that numerous superior multiphase(AgCuTe,Ag_(−2)Te,copper telluride(Cu_(2)Te and Cu_(2−x)Te),and nickel telluride(NiTe))interfaces with simultaneous strong phonon scattering and weak electron scattering could be realized in AgCuTe-based TE materials.Owing to the similar chemical bonds in these phases,the depletion region at phase interfaces,which acts as carrier scattering centers,could be ignored.Therefore,the power factor(PF)is obviously enhanced from~609 to~832μW·m^(−1)·K^(−2),and k is simultaneously decreased from~0.52 to~0.43 W·m^(−1)·K^(−1) at 636 K.Finally,a peak figure of merit(zT)of~1.23 at 636 K and an average zT(zTavg)of~1.12 in the temperature range of 523–623 K are achieved,which are one of the best values among the AgCuTe-based TE materials.This study could provide new guidance to enhance the performance by designing superior multiphase interfaces in the TE materials.展开更多
The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattic...The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattice thermal conductivity and poor Seebeck coefficient lead to low energy conversion effi-ciency.Filling Yb into the lattice void to optimize the band structure and regulate the chemical po-tential is an indispensable means for improving the thermoelectric properties of CoSb_(3)-based materials,while the phase structure and thermoelectric properties vary with the preparation process.This motivates the current work to focus on the influence of annealing temperature on the microstructure and thermoelectric properties of Yb-filled CoSb_(3).Experimental analysis and theoretical model eluci-dated that an increase in annealing temperature can optimize the Yb filling fraction,which simulta-neously manipulates the band structure as well as chemical potential,resulting in an excellent electrical property.Furthermore,the phase and microstructure characterization clarify that the annealing temperature can effectively affect the grain size.The complex grain boundary induced by grain refinement,more filled Yb atoms and precipitates strongly scatter wide-frequency phonons,significantly suppressing the lattice thermal conductivity.As a result,a superior dimensionless figure of merit(ZT)value of~1.33 at 823 K and an average ZTave of~0.9(323-823 K)were achieved in the Ybo.4Co4Sb12 sample annealed at 923 K,and the calculated conversion efficiency could reach~13%.This work pro-vides a unique paradigm to improve thermoelectrics in the filled CoSb_(3)-based skutterudites by annealing engineering.展开更多
基金the Graduate Scientific Research and Innovation Foundation of Chongqing,China(No.CYB 19064)the National Natural Science Foundation of China(Nos.51772035,11674040,51472036 and 51672270)+4 种基金the Fundamental Research Funds for the Central Universities(No.106112017CDJQJ308821)the Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSW-SLH016)the CSC Scholarship(No.201806050180)2019 ITS Summer Fellowship,the Natural Science Foundation of Chongqing,China(No.cstc2019jcyj-msxmX0554)the Starting Research Fund from Chongqing University。
文摘Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance.Herein,the thermoelectric properties of nominal Bi_(1-x)Cu_(x)Se samples were studied as the functions of the content of Cu additive and temperature.It is found that Cu additives in BiSe(1)profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process,(2)increase considerably the effective mass and thus the Seebeck coefficient,and(3)yield point defects and Cu-Se secondary phases that effectively scatter heat-carrying phonons.As a result,the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT~0.29 in Bi_(1-x)Cu_(x)Se(x=0.03)sample at 467 K in parallel to the pressure direction and a zT~0.20 at 468 K in the perpendicular direction.
基金Dr.K.H.Lim acknowledges the financial support of the National Natural Science Foundation of China(Grant No.22208293)Research Funds of the Institute of Zhejiang University-Quzhou(Nos.IZQ2021RCZX003,IZQ2021RCZX002,IZQ2021KJ2024,IZQ2022KYZX09)+3 种基金supported by the State Key Laboratory of Fluorinated Greenhouse gases Replacement and Treatment(No.SKLFGGRT2022001)the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23201)Dr.Y.Liu acknowledges funding from the National Natural Science Foundation of China(NSFC)(Grants No.22209034)the Innovation and Entrepreneurship Project of Overseas Returnees in Anhui Province(Grants No.2022LCX002)。
文摘The commercial viability of thermoelectric(TE)devices relies heavily on two factors:cost reduction and efficiency enhancement.In this study,we first produce p-type Cu_(12)Sb_(4)S_(16-x)(x=0,3,4)using a low-temperature bottom-up approach and demonstrate Cu_(12)Sb_(4)S_(13)to show the best TE performance among the three tested compositions.Subsequently,the TE energy conversion efficiency of Cu_(12)Sb_(4)S_(13)is further enhanced by optimizing its electronic band structure through the incorporation of small amounts of tel-lurium.At an optimal Te content of 5 mol%,more than a twofold increase in the TE figure of merit(zT)is obtained.To gain insight into the mechanism of improvement on the transport properties of the mate-rial,we compare the interphase transport mechanism by incorporating nanodomains of different metals(Ag and Cu)into the Cu_(12)Sb_(4)S_(13)matrix.The improved electrical conductivity obtained with Cu_(12)Sb_(4)S_(13)-Te nanocomposites is attributed to a charge flooding of the Cu_(12)Sb_(4)S_(13)surface.In contrast,excessive down-ward band-bending at the interphases of Ag/Cu metal-semiconductor drastically reduces the electrical conductivity.Besides,a weighted mobility(μw)analysis shows a dominant thermal activation of carri-ers in Cu_(12)Sb_(4)S_(13)-Te nanocomposites.In this material,a strong decrease in lattice thermal conductivity is also found,which is associated with a phonon-carrier scattering mechanism.Our work shows the impor-tance of proper band-engineering in TE nanocomposites to decouple electrical and thermal transport to enhance TE performance,and the efficacy ofμw for electrical and thermal transport analysis.
基金supported by National Natural Science Foundation of China(52250090,52371208,51571007,51772012)the Beijing Natural Science Foundation(JQ18004),111 Project(B17002)L D Z appreciates the National Science Fund for Distinguished Young Scholars(51925101).
文摘Recently,off-centering behavior has been discovered in a series of thermoelectric materials.This behavior indicates that the constituent atoms of the lattice displace from their coordination centers,leading to the locally distorted state and local symmetry breaking,while the material still retains its original crystallographic symmetry.This effect has been proved to be the root cause of ultralow thermal conductivity in off-centering materials,and is considered as an effective tool to regulate the thermal conductivity and improve the thermoelectric performance.Herein,we present a collection of recently discovered off-centering compounds,discuss their electronic origins and local coordination structures,and illuminate the underlying mechanism of the off-centering effect on phonon transport and thermal conductivity.This paper presents a comprehensive view of our current understanding to the off-centering effect,and provides a new idea for designing high performance thermoelectrics.
基金Project supported by the National Natural Science Foundation of China(Grant No.52206092)the Natural Science Foundation of Jiangsu Province+5 种基金China(Grant No.BK20210565)funded by the Department of Science and Technology of Jiangsu Province(Grant No.BK20220032)the Basic Science(Natural Science)Research Project of Higher Education Institutions of Jiangsu Province,China(Grant No.21KJB470009)Nanjing Science and Technology Innovation Project for Overseas Studentsthe“Shuangchuang”Doctor Program of Jiangsu Province,China(Grant No.JSSCBS20210315)the Open Research Fund of Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments,Southeast University(Grant No.KF202010)。
文摘Phonon bandgap typically has a significant effect on phonon-phonon scattering process.In this work,the effects of mass modified phonon bandgap inθ-phase Ta N are systemically investigated by the means of first-principles calculations with linearized Boltzmann transport equation.Through detailed calculations,we find that phonon bandgap has a significant effect on three-phonon process while exhibits a much weaker effect on four-phonon process.The reason for the ultrahigh thermal conductivity ofθ-phase Ta N is the long lifetime of phonons including both three-phonon and four-phonon processes,which originates from the weak phonon anharmonicity and large phonon bandgap-induced small phonon-phonon scattering phase space.This work advances the understanding of phonon bandgap effects on phonon transport.
基金National Key Research and Development Program of China(Grant No.2017YFA0206000)eijing Natural Science Foundation(Grant No.Z180011)+1 种基金National Science Foundation of China(Grant Nos.12027807,12104241 and 61521004)roject funded by China Postdoctoral Science Foundation(Grant No.2019M660283)。
文摘Two dimensional excitonic devices are of great potential to overcome the dilemma of response time and integration in current generation of electron or/and photon based systems.The ultrashort diffusion length of exciton arising from ultrafast relaxation and low carrier mobility greatly discounts the performance of excitonic devices.Phonon scattering and exciton localization are crucial to understand the modulation of exciton flux in two dimensional disorder energy landscape,which still remain elusive.Here,we report an optimized scheme for exciton diffusion and relaxation dominated by phonon scattering and disorder potentials in WSe2 monolayers.The effective diffusion coefficient is enhanced by>200%at 280 K.The excitons tend to be localized by disorder potentials accompanied by the steadily weakening of phonon scattering when temperature drops to 260 K,and the onset of exciton localization brings forward as decreasing temperature.These findings identify that phonon scattering and disorder potentials are of great importance for long-range exciton diffusion and thermal management in exciton based systems,and lay a firm foundation for the development of functional excitonic devices.
基金supported by National Key Research and Development Program of China(No.2017YFE0198000,2022YFE0119100).National Natural Science Foundation of China(Grant No.U21A2054,52273285,52061009,52262032).Guangxi Science and Technology Project(Grant No.AD21220056).
文摘SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectric transport parameters to achieve high thermoelectric properties of p-type SiGe in the mid-temperature region by incorporating nano-TaC into SiGe combined ball milling with spark plasma sintering.By optimizing the amount of TaC in the SiGe matrix,the power factors were significantly increased due to the modulation doping effect based on the work function matching of SiGe with TaC.Simultaneously,the ensemble effect of the nanostructure leads to a significant decrease in thermal conductivity.Thus,a high ZT of 1.06 was accomplished at 873 K,which is 64%higher than that of typical radioisotope thermoelectric generator.Our research offers a novel strategy for expanding and enhancing the thermoelectric properties of SiGe materials in the medium temperature range.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.52262032,52273285,51961011,52061009,and U21A2054)the National Key R&D Program of China(Grant No.2022YFE0119100)。
文摘It is common sense that a phase interface(or grain boundary)could be used to scatter phonons in thermoelectric(TE)materials,resulting in low thermal conductivity(k).However,a large number of impurity phases are always so harmful to the transport of carriers that poor TE performance is obtained.Here,we demonstrate that numerous superior multiphase(AgCuTe,Ag_(−2)Te,copper telluride(Cu_(2)Te and Cu_(2−x)Te),and nickel telluride(NiTe))interfaces with simultaneous strong phonon scattering and weak electron scattering could be realized in AgCuTe-based TE materials.Owing to the similar chemical bonds in these phases,the depletion region at phase interfaces,which acts as carrier scattering centers,could be ignored.Therefore,the power factor(PF)is obviously enhanced from~609 to~832μW·m^(−1)·K^(−2),and k is simultaneously decreased from~0.52 to~0.43 W·m^(−1)·K^(−1) at 636 K.Finally,a peak figure of merit(zT)of~1.23 at 636 K and an average zT(zTavg)of~1.12 in the temperature range of 523–623 K are achieved,which are one of the best values among the AgCuTe-based TE materials.This study could provide new guidance to enhance the performance by designing superior multiphase interfaces in the TE materials.
基金supported by the National Key Research and Development Program of China (Grant Nos.2018YFA0702100 and 2022YFB3803900)the Joint Funds of the National Natural Science Foundation of China and the Chinese Academy of Sciences (CAS)’Large-Scale Scientific Facility (Grant No.U1932106)the Sichuan University Innovation Research Pro-gram of China (Grant No.2020SCUNL112).
文摘The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattice thermal conductivity and poor Seebeck coefficient lead to low energy conversion effi-ciency.Filling Yb into the lattice void to optimize the band structure and regulate the chemical po-tential is an indispensable means for improving the thermoelectric properties of CoSb_(3)-based materials,while the phase structure and thermoelectric properties vary with the preparation process.This motivates the current work to focus on the influence of annealing temperature on the microstructure and thermoelectric properties of Yb-filled CoSb_(3).Experimental analysis and theoretical model eluci-dated that an increase in annealing temperature can optimize the Yb filling fraction,which simulta-neously manipulates the band structure as well as chemical potential,resulting in an excellent electrical property.Furthermore,the phase and microstructure characterization clarify that the annealing temperature can effectively affect the grain size.The complex grain boundary induced by grain refinement,more filled Yb atoms and precipitates strongly scatter wide-frequency phonons,significantly suppressing the lattice thermal conductivity.As a result,a superior dimensionless figure of merit(ZT)value of~1.33 at 823 K and an average ZTave of~0.9(323-823 K)were achieved in the Ybo.4Co4Sb12 sample annealed at 923 K,and the calculated conversion efficiency could reach~13%.This work pro-vides a unique paradigm to improve thermoelectrics in the filled CoSb_(3)-based skutterudites by annealing engineering.
基金supported by the National Key R&D Program of China (2019YFA0704903)the National Natural Science Foundation of China (11834012, 52172232, 52130203, and 91963122)Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory (XHT2020-004)。
