Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle...Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.展开更多
Reducing thermal conductivity while avoiding adverse interfacial reactions during sintering is crucial for improving the thermoelectric performance of Bi_(2)Te_(3)based composites.Inert ceramic nanoparticles are good ...Reducing thermal conductivity while avoiding adverse interfacial reactions during sintering is crucial for improving the thermoelectric performance of Bi_(2)Te_(3)based composites.Inert ceramic nanoparticles are good candidates for achieving this goal.In this study,we designed and prepared a series of p-type Bi_(0.5)Sb_(1.5)Te_(3)nanocomposites decorated with Y_(2)O_(3)ceramic nanoparticles via ball-milling dispersion and spark-plasma sintering.Owing to the chemical stability of the ceramics,no traces of atomic doping or interfacial reactions were observed.Transport measurements revealed that the Y_(2)O_(3)nanoparticles distributed along the grain boundaries acted as energy-dependent carrier-filtering centers to improve the scattering parameter and Seebeck coefficient,contributing to the elevated power factor even with a decreased electrical conductivity.Moreover,the incorporated Y_(2)O_(3)nanoparticles and various defect structures they induced effectively strengthened the phonon scattering and suppressed the lattice thermal conductivity.Consequently,a peak figure of merit(ZT)of 1.23 at 313 K was achieved for 0.4%Y_(2)O_(3)/Bi_(0.5)Sb_(1.5)Te_(3),which is 13%higher than that of the matrix.In addition,the Vickers hardness of the composite material was 35%higher than that of the matrix.This study demonstrates the effectiveness of ceramic nanoparticles in synergistic ally improving the thermoelectric and mechanical properties,which may be further extended to other thermoelectric systems.展开更多
Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a p...Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a poor thermoelectric performance because of its low electrical conductivity of about 3×10^(2)S/m at room temperature.In this work,In and Se co-doping was carried out to optimize the thermoelectric perfor-mance of n-type Mg_(3)Sb_(1.5)Bi_(0.5)-based material.The experimental results revealed that the carrier con-centration and mobility of Mg_(3)Sb_(1.5)Bi_(0.5)significantly increased after In and Se co-doping,leading to an improvement of power factor.Simultaneously,lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg.A maximum zT of 1.64 at 723 K was obtained for the Mg_(3.17)In_(0.03)Sb_(1.5)Bi_(0.49)Se_(0.01)sample.And an average zT value of about 1.1 between 300 and 723 K was achieved,which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.展开更多
Recently,n-type Mg3Sb1.5Bi0.5-based thermoelectric materials have attracted considerable attention for their extraordinary thermoelectric performance.Ideally,thermoelectric generators should be made of the same materi...Recently,n-type Mg3Sb1.5Bi0.5-based thermoelectric materials have attracted considerable attention for their extraordinary thermoelectric performance.Ideally,thermoelectric generators should be made of the same material system to avoid thermal mismatch in the practical application.In this work,p-type Mg3Sb1.5Bi0.5 which has almost the same composition as the state-of-the-art n-type Mg3.2Sb1.5Bi0.49-Te0.01Mn0.01 was synthesized by ball milling and spark plasma sintering,and then Na was chosen as an acceptor dopant to optimize the carrier concentration and further improve the thermoelectric performance.Na0.0075Mg2.9925Sb1.5Bi0.5 sample gets the highest ZT of~0.5 at 773 K.While Na0.005Mg2.995Sb1.5Bi0.5 sample shows the highest average ZT of~0.29 in the temperature range of 300 e773 K and matched thermal expansion behavior with the state-of-the-art n-type Mg3.2Sb1.5Bi0.49-Te0.01Mn0.01,which is of great significance for practical applications.Taking the Joule and Thompson heat into account,a high theoretical conversion efficiency(η)of~9.5%was calculated for the thermoelectric module consists of the present p-type Na0.005Mg2.995Sb1.5Bi0.5 and the state-of-the-art n-type Mg3.2Sb1.5Bi0.49Te0.01Mn0.01 with the leg length of 2 mm,and cold and hot side temperature of 300 K and 773 K,respectively,which shows a good potential for the use of this class of materials in the midtemperature power generation applications.展开更多
Composites were prepared,through hot pressing,using carbon materials with different pore size distributions as additives for commercial Bi_(0.5)Sb_(1.5)Te_(3) thermoelectric material(BST,p-type).Thermoelectric propert...Composites were prepared,through hot pressing,using carbon materials with different pore size distributions as additives for commercial Bi_(0.5)Sb_(1.5)Te_(3) thermoelectric material(BST,p-type).Thermoelectric properties of the composites were measured in a temperature range of 298-473 K.Thermal conductivity of the composites,especially lattice thermal conductivity,was effectively decreased due to the mesoporous properties of the incorporated carbon additives.The electrical conductivity of the composites slightly decreased due to the electron scattering at the interface between the carbon material and the commercial BST matrix.The composite with 0.2 vol.%mesoporous carbon powder(36%mesoporosity)exhibited a figure of merit value approximately 10.7%higher than that of commercial BST without additives.This behavior resulted in 116%improved output power in the composite block-based single element compared with a bare BST thermoelectric block.The enhanced figure of merit was attributed to the effective reduction of lattice thermal conductivity by acoustic phonons scattering at the interface between the BST matrix and the mesoporous carbon as well as at the pore surfaces within the mesoporous carbon.By utilizing mesoporous carbon materials used in this study,the shortcomings and economic difficulties of the composite process with low dimensional carbon additives(carbon nanotubes,graphene,and nanodiamond)can be overcome for extensive practical applications.Mesoporous carbon powder with a tailored porosity distribution revealed the validity of bulk-type carbon additives to enhance the figure of merit of commercial thermoelectric materials.展开更多
（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） thermoelectric material was sintered via a field activated and pressure assisted sintering（FAPAS） process.By applying different current intensity（0,60,320 A/cm^2） in the si...（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） thermoelectric material was sintered via a field activated and pressure assisted sintering（FAPAS） process.By applying different current intensity（0,60,320 A/cm^2） in the sintering process,the effects of electric current on the microstructure and thermoelectric performance were investigated.This demonstrated that the application of electric current in the sintering process could significantly improve the uniformity and density of（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） samples.When the current intensity was raised to 320 A/cm^2,the preferred orientation of grains was observed.Moreover,positive effects on the thermoelectric performance of applying electric current in the sintering process were also confirmed.An increase of 0.02 and 0.11 in the maximum figure of merit ZT value could be acquired by applying current of 60 and 320 A/cm^2,respectively.展开更多
Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements,green environmental protection,and lower price.In recent years,the thermoelectric properties of n-typ...Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements,green environmental protection,and lower price.In recent years,the thermoelectric properties of n-type Mg_(3)Sb_(2) materials have been optimized by doping chalcogenide elements(S,Se,and Te)at the anionic position.In this work,n-type Mg_(3.2)A_(x)Sb_(1.5)Bi_(0.5)(A=Gd,Ho;x=0.01,0.02,0.03,and 0.4)samples were prepared by the cation site doping of lanthanide elements(Gd and Ho).The research results show that Gd and Ho doped n-type Mg3.2Sb1.5Bi0.5samples are entirely comparable to the S,Se,and Te doped n-type Mg3.2Sb1.5Bi0.5samples,demonstrating more excellent thermoelectric properties.Doping with lanthanides(Gd and Ho)at the Mg site increases the carrier concentration of the material to 8.161×10^(19)cm^(-3).Doping induces the contribution of more electron,thus obtaining higher conductivity.The maximum zT value of the Mg_(3.2)Gd_(0.02)Sb_(1.5)Bi_(0.5) and the Mg_(3.2)Ho_(0.02)Sb_(1.5)Bi_(0.5) samples reaches 1.61 and 1.55,respectively.This work theoretically and experimentally demonstrates Gd and Ho are efficient n-type dopants for Mg_(3.2)Sb_(1.5)Bi_(0.5) thermoelectric material.展开更多
Room-temperature thermoelectric materials provide promising solutions for energy harvesting from the environment,and deliver a maintenance-free power supply for the internet-of-things(IoTs).The currently available Bi_...Room-temperature thermoelectric materials provide promising solutions for energy harvesting from the environment,and deliver a maintenance-free power supply for the internet-of-things(IoTs).The currently available Bi_(2)Te_(3) family discovered in the 1950s,still dominates industrial applications,however,it has serious disadvantages of brittleness and the resource shortage of tellurium(1×10^(-3) ppm in the earth's crust).The novel Mg_(3)Sb_(2) family has received increasing attention as a promising alternative for room-temperature thermoelectric materials.In this review,the development timeline and fabrication strategies of the Mg 3 Sb 2 family are depicted.Moreover,an insightful comparison between the crystal-linity and band structures of Mg_(3)Sb_(2) and Bi_(2)Te_(3) is drawn.An outlook is presented to discuss challenges and new paradigms in designing room-temperature thermoelectric materials.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62074036,61674038,and 11574302)the Foreign Cooperation Project of Fujian Province,China(Grant No.2023I0005)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(Grant No.KF202108)the National Key Research and Development Program of China(Grant No.2016YFB0402303)the Foundation of Fujian Provincial Department of Industry and Information Technology of China(Grant No.82318075)。
文摘Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.
基金financially supported by the National Natural Science Foundation of China(Nos.11834012 and 52130203)。
文摘Reducing thermal conductivity while avoiding adverse interfacial reactions during sintering is crucial for improving the thermoelectric performance of Bi_(2)Te_(3)based composites.Inert ceramic nanoparticles are good candidates for achieving this goal.In this study,we designed and prepared a series of p-type Bi_(0.5)Sb_(1.5)Te_(3)nanocomposites decorated with Y_(2)O_(3)ceramic nanoparticles via ball-milling dispersion and spark-plasma sintering.Owing to the chemical stability of the ceramics,no traces of atomic doping or interfacial reactions were observed.Transport measurements revealed that the Y_(2)O_(3)nanoparticles distributed along the grain boundaries acted as energy-dependent carrier-filtering centers to improve the scattering parameter and Seebeck coefficient,contributing to the elevated power factor even with a decreased electrical conductivity.Moreover,the incorporated Y_(2)O_(3)nanoparticles and various defect structures they induced effectively strengthened the phonon scattering and suppressed the lattice thermal conductivity.Consequently,a peak figure of merit(ZT)of 1.23 at 313 K was achieved for 0.4%Y_(2)O_(3)/Bi_(0.5)Sb_(1.5)Te_(3),which is 13%higher than that of the matrix.In addition,the Vickers hardness of the composite material was 35%higher than that of the matrix.This study demonstrates the effectiveness of ceramic nanoparticles in synergistic ally improving the thermoelectric and mechanical properties,which may be further extended to other thermoelectric systems.
基金supported by the Chunhui Program of the Education Ministry of China,and that at the University of Electronic Science and Technology of China was funded by the Department of Science and Technology of Sichuan Province(2021JDTD0030)the National Natural Science Foundation of China(No.62104032,No.62174022).
文摘Mg_(3)Sb_(1.5)Bi_(0.5)-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements.However,pure and intrinsic Mg_(3)Sb_(1.5)Bi_(0.5)manifests a poor thermoelectric performance because of its low electrical conductivity of about 3×10^(2)S/m at room temperature.In this work,In and Se co-doping was carried out to optimize the thermoelectric perfor-mance of n-type Mg_(3)Sb_(1.5)Bi_(0.5)-based material.The experimental results revealed that the carrier con-centration and mobility of Mg_(3)Sb_(1.5)Bi_(0.5)significantly increased after In and Se co-doping,leading to an improvement of power factor.Simultaneously,lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg.A maximum zT of 1.64 at 723 K was obtained for the Mg_(3.17)In_(0.03)Sb_(1.5)Bi_(0.49)Se_(0.01)sample.And an average zT value of about 1.1 between 300 and 723 K was achieved,which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.
基金the National Natural Science Foundation of China(Nos.51771065 and 51871082).
文摘Recently,n-type Mg3Sb1.5Bi0.5-based thermoelectric materials have attracted considerable attention for their extraordinary thermoelectric performance.Ideally,thermoelectric generators should be made of the same material system to avoid thermal mismatch in the practical application.In this work,p-type Mg3Sb1.5Bi0.5 which has almost the same composition as the state-of-the-art n-type Mg3.2Sb1.5Bi0.49-Te0.01Mn0.01 was synthesized by ball milling and spark plasma sintering,and then Na was chosen as an acceptor dopant to optimize the carrier concentration and further improve the thermoelectric performance.Na0.0075Mg2.9925Sb1.5Bi0.5 sample gets the highest ZT of~0.5 at 773 K.While Na0.005Mg2.995Sb1.5Bi0.5 sample shows the highest average ZT of~0.29 in the temperature range of 300 e773 K and matched thermal expansion behavior with the state-of-the-art n-type Mg3.2Sb1.5Bi0.49-Te0.01Mn0.01,which is of great significance for practical applications.Taking the Joule and Thompson heat into account,a high theoretical conversion efficiency(η)of~9.5%was calculated for the thermoelectric module consists of the present p-type Na0.005Mg2.995Sb1.5Bi0.5 and the state-of-the-art n-type Mg3.2Sb1.5Bi0.49Te0.01Mn0.01 with the leg length of 2 mm,and cold and hot side temperature of 300 K and 773 K,respectively,which shows a good potential for the use of this class of materials in the midtemperature power generation applications.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.NRF-2018R1A4A1022260)。
文摘Composites were prepared,through hot pressing,using carbon materials with different pore size distributions as additives for commercial Bi_(0.5)Sb_(1.5)Te_(3) thermoelectric material(BST,p-type).Thermoelectric properties of the composites were measured in a temperature range of 298-473 K.Thermal conductivity of the composites,especially lattice thermal conductivity,was effectively decreased due to the mesoporous properties of the incorporated carbon additives.The electrical conductivity of the composites slightly decreased due to the electron scattering at the interface between the carbon material and the commercial BST matrix.The composite with 0.2 vol.%mesoporous carbon powder(36%mesoporosity)exhibited a figure of merit value approximately 10.7%higher than that of commercial BST without additives.This behavior resulted in 116%improved output power in the composite block-based single element compared with a bare BST thermoelectric block.The enhanced figure of merit was attributed to the effective reduction of lattice thermal conductivity by acoustic phonons scattering at the interface between the BST matrix and the mesoporous carbon as well as at the pore surfaces within the mesoporous carbon.By utilizing mesoporous carbon materials used in this study,the shortcomings and economic difficulties of the composite process with low dimensional carbon additives(carbon nanotubes,graphene,and nanodiamond)can be overcome for extensive practical applications.Mesoporous carbon powder with a tailored porosity distribution revealed the validity of bulk-type carbon additives to enhance the figure of merit of commercial thermoelectric materials.
基金Project support by the National Research Program of China(No.50975190)
文摘（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） thermoelectric material was sintered via a field activated and pressure assisted sintering（FAPAS） process.By applying different current intensity（0,60,320 A/cm^2） in the sintering process,the effects of electric current on the microstructure and thermoelectric performance were investigated.This demonstrated that the application of electric current in the sintering process could significantly improve the uniformity and density of（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） samples.When the current intensity was raised to 320 A/cm^2,the preferred orientation of grains was observed.Moreover,positive effects on the thermoelectric performance of applying electric current in the sintering process were also confirmed.An increase of 0.02 and 0.11 in the maximum figure of merit ZT value could be acquired by applying current of 60 and 320 A/cm^2,respectively.
基金the National Natural Science Foundation of China(No.51871240)。
文摘Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements,green environmental protection,and lower price.In recent years,the thermoelectric properties of n-type Mg_(3)Sb_(2) materials have been optimized by doping chalcogenide elements(S,Se,and Te)at the anionic position.In this work,n-type Mg_(3.2)A_(x)Sb_(1.5)Bi_(0.5)(A=Gd,Ho;x=0.01,0.02,0.03,and 0.4)samples were prepared by the cation site doping of lanthanide elements(Gd and Ho).The research results show that Gd and Ho doped n-type Mg3.2Sb1.5Bi0.5samples are entirely comparable to the S,Se,and Te doped n-type Mg3.2Sb1.5Bi0.5samples,demonstrating more excellent thermoelectric properties.Doping with lanthanides(Gd and Ho)at the Mg site increases the carrier concentration of the material to 8.161×10^(19)cm^(-3).Doping induces the contribution of more electron,thus obtaining higher conductivity.The maximum zT value of the Mg_(3.2)Gd_(0.02)Sb_(1.5)Bi_(0.5) and the Mg_(3.2)Ho_(0.02)Sb_(1.5)Bi_(0.5) samples reaches 1.61 and 1.55,respectively.This work theoretically and experimentally demonstrates Gd and Ho are efficient n-type dopants for Mg_(3.2)Sb_(1.5)Bi_(0.5) thermoelectric material.
基金This work was supported by the Natural Science Foundation of China(grant number 51872133)National Key Research and Development Program of China(grant number 2019YFA0704900,2018YFB0703600)the Tencent Foundation through the XPLORER PRIZE and Shenzhen DRC project(grant number[2018]1433).
文摘Room-temperature thermoelectric materials provide promising solutions for energy harvesting from the environment,and deliver a maintenance-free power supply for the internet-of-things(IoTs).The currently available Bi_(2)Te_(3) family discovered in the 1950s,still dominates industrial applications,however,it has serious disadvantages of brittleness and the resource shortage of tellurium(1×10^(-3) ppm in the earth's crust).The novel Mg_(3)Sb_(2) family has received increasing attention as a promising alternative for room-temperature thermoelectric materials.In this review,the development timeline and fabrication strategies of the Mg 3 Sb 2 family are depicted.Moreover,an insightful comparison between the crystal-linity and band structures of Mg_(3)Sb_(2) and Bi_(2)Te_(3) is drawn.An outlook is presented to discuss challenges and new paradigms in designing room-temperature thermoelectric materials.
