A new basic electrolyte with two cationic plating additives, polydiaminourea and polyaminosulfone, was investigated for the electrochemical deposition of the bismuth telluride film on a nickel-plated copper foil. Tell...A new basic electrolyte with two cationic plating additives, polydiaminourea and polyaminosulfone, was investigated for the electrochemical deposition of the bismuth telluride film on a nickel-plated copper foil. Tellurium starts to deposit at a higher potential （-0.35 V） than bismuth （-0.5 V） in this electrolyte. The tellurium-to-bismuth ratio increases while the deposition potential declines from -1 to -1.25 V, indicating a kinetically quicker bismuth deposition at higher potentials. The as-deposited film features good adhesion to the substrate and smooth morphology, and has a nearly amorphous crystal structure disclosed by X-ray diffraction patterns.展开更多
Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply.It is noted that thermoelectric power generators are easy to damag...Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply.It is noted that thermoelectric power generators are easy to damage in the dynamic service process,resulting in the formation of microcracks and performance degradation.Herein,we prepare a new hybrid hydrogel thermoelectric material PAAc/XG/Bi_(2)Se_(0.3)Te_(2.7)by an in situ polymerization method,which shows a high stretchable and self-healable performance,as well as a good thermoelectric performance.For the sample with Bi_(2)Se_(0.3)Te_(2.7)content of 1.5 wt%(i.e.,PAAc/XG/Bi2Se0.3Te27(1.5 wt%)),which has a room temperature Seebeck coefficient of-0.45 mV K^(-1),and exhibits an open-circuit voltage of-17.91 mV and output power of 38.1 nW at a temperature difference of 40 K.After being completely cut off,the hybrid thermoelectric hydrogel automatically recovers its electrical characteristics within a response time of 2.0 s,and the healed hydrogel remains more than 99%of its initial power output.Such stretchable and self-healable hybrid hydrogel thermoelectric materials show promising potential for application in dynamic service conditions,such as wearable electronics.展开更多
Bismuth telluride-based alloys are the most widely used commercial thermoelectric(TE)material for room temperature refrigeration.Here,we successfully shift up the optimum figure of merit of n-type bismuth-telluride-ba...Bismuth telluride-based alloys are the most widely used commercial thermoelectric(TE)material for room temperature refrigeration.Here,we successfully shift up the optimum figure of merit of n-type bismuth-telluride-based TE materials for mid-temperature power generation.SbI_(3)doping is used to regulate the carrier concentration and Indium alloying to increase the bandgap,suppressing the detrimental bipolar conduction in the mid-temperature range.The lattice thermal conductivity is significantly reduced due to the multiscale microstructures induced via hot deformation.As a result,a peak zT of~1.1 was attained at 625 K for Bi_(1.85)In_(0.15)Te_(2)Se+0.25 wt%SbI_(3)alloy after hot deformation,showing a great application prospect of this alloy in mid-temperature TE power generation.展开更多
Thin films of Bismuth Telluride (Bi<sub>2</sub>Te<sub>3</sub>) are prepared by thermal evaporation from nanopowders on the glass substrates. The XRD patterns of films show that all the films ar...Thin films of Bismuth Telluride (Bi<sub>2</sub>Te<sub>3</sub>) are prepared by thermal evaporation from nanopowders on the glass substrates. The XRD patterns of films show that all the films are polycrystalline and the crystalline increased by annealing temperature. Measuring of the thermoelectric power of thin films in the temperature range 300 to 380 K shows that Seebeck Coefficients have both negative and positive values, indicating that the films have both n-type and p-type conductivity. The re-crystallization of films is done by annealing from 130°C to 175°C and Seebeck Coefficient varied from -150 to 100 μV/K.展开更多
The density junction theory and discrete variation method ( DFT - DVM) was used to study correlation between composition, structure, chemical bond, and property of thermoelectrics of Bi-Sb-Te series. 8 models of Bi20-...The density junction theory and discrete variation method ( DFT - DVM) was used to study correlation between composition, structure, chemical bond, and property of thermoelectrics of Bi-Sb-Te series. 8 models of Bi20-xSbxTe32(x = 0,2,6,8,12,14,18 and 20) were calculated. The results show that there is less difference in the ionic bonds between Te( I)-Bi(Sb) and Te(Ⅱ)-Bi(Sb) , but the covalent bond of Te(Ⅰ)-Bi( Sb ) is stronger than that of Te(Ⅱ)-Bi( Sb ) . The interaction between Te(Ⅰ) and Te(Ⅰ) in different layers is the weakest and the interaction should be Van Der Wools power. The charge of Sb is lower than that of Bi, and the ionic bond of Te-Sb is weaker than that of Te-Bi. The covalent bond of Te-Sb is also weaker than that of Te-Bi. Therefore, the thermoelectric property may be imfiroved by adjusting the electrical conductivity and thermal conductivity through changing the composition in the compounds of Bi-Sb-Te. The calculated results are consistent with the experiments.展开更多
A kind of p-type segmented Bi2 Te3/CoSB3 thermoetectric material was preparea oy sparse ptasma sintering（ SPS ） . When the segmented materials were used at the temperature ranging from 300 K to 800 K, the junction t...A kind of p-type segmented Bi2 Te3/CoSB3 thermoetectric material was preparea oy sparse ptasma sintering（ SPS ） . When the segmented materials were used at the temperature ranging from 300 K to 800 K, the junction temperature was optimized, which is about 500 K, and the corresponding length ratio of CoSb3 to Bi2 Te3 is about 15 ： 2. The measured maximum power output of segmented materials is abont 320 W·m^-2, which is about 1.8 times as high as that of monolithic material CoSb3 under the same measuring conditions.展开更多
Anisotropy and inhomogeneity are ubiquitous in spark plasma sintered thermoelectric devices.However,the origin of inhomogeneity in thermoelectric nanocomposites has rarely been investigated so far.Herein,we systematic...Anisotropy and inhomogeneity are ubiquitous in spark plasma sintered thermoelectric devices.However,the origin of inhomogeneity in thermoelectric nanocomposites has rarely been investigated so far.Herein,we systematically study the impact of inhomogeneity in spark plasma sintered bismuth antimony telluride(BiSbTe)thermoelectric nanocomposites fabricated from solution-synthesized nanoplates.The figure of merit can reach 1.18,which,however,can be overestimated to 1.88 without considering the inhomogeneity.Our study reveals that the inhomogeneity in thermoelectric properties is attributed to the non-uniformity of porosity,textures and elemental distribution from electron backscatter diffraction and energy-dispersive spectroscopy characterizations.This finding suggests that the optimization of bulk material homogeneity should also be actively pursued in any future thermoelectric material research.展开更多
Bi2-xSbxTe3 thermoelectric films were electrochemically deposited from the solution containing Bi^3＋, HTeO2^＋and SbO^＋. ESEM （environmental scanning electron microscope） investigations indicated that the crystall...Bi2-xSbxTe3 thermoelectric films were electrochemically deposited from the solution containing Bi^3＋, HTeO2^＋and SbO^＋. ESEM （environmental scanning electron microscope） investigations indicated that the crystalline state of Bi2-xSbxTe3 films transformed from equiaxed crystal to dendritic crystal with the negative shift of deposition potential. XRD and EDS were used to characterize the structure and composition of the electrodeposited films. The Seebeck coefficient and the temperature dependence of the resistance of Bi2-xSbxTe3 films were measured. The results showed that the composition of the film electrodeposited at -0.5 V is Bi2-xSbxTe3 with the largest Seebeck coefficient of 213 μV·K^-1.展开更多
Alloys of Bi_(2)Te_(3) and Sb_(2)Te_(3) are the best performing p-type thermoelectrics near room temperature and have been the subject of extensive engineering efforts.Dramatic improvement is achieved by introducing d...Alloys of Bi_(2)Te_(3) and Sb_(2)Te_(3) are the best performing p-type thermoelectrics near room temperature and have been the subject of extensive engineering efforts.Dramatic improvement is achieved by introducing defects that effectively scatter phonons and reduce thermal conductivity.Unfortunately,outstanding results are often difficult to reproduce as the process variables involved are difficult to control or possibly unknown.Here,a reproducible and controllable method of fabricating porous Bi_(0.5)Sb_(1.5)Te_(3+x) is presented.While effective medium theory(EMT)predicts no benefit,improvements in the thermoelectric quality factor,B(which determines the maximum zT of a materials),were as high as 45% parallel to the pressing direction for a sample of roughly 20% porosity.The study of microstructural evolution with increasing porosity is facilitated by a combination of Scanning/Transmission Electron Microscopy(S/TEM)and Electron Backscattered Diffraction(EBSD).This study reveals a statistically significant shift in the distribution of grain boundaries favoring lower energy twins,which coincides with an increase in the presence of stepped twin boundaries.This work demonstrates the potential benefits of careful grain boundary engineering and the need for further detailed studies of the dependence of thermal and electrical transport on grain boundary structure and orientation in these alloys.展开更多
Bismuth antimony telluride(Bi_(2–x)Sb_(x)Te_(3))is commonly used for thermoelectric generation at temperatures near ambient temperature.Here,we report incorporating reduced graphene oxide(rGO)and Cu_(2)Se_(0.98)Te_(0...Bismuth antimony telluride(Bi_(2–x)Sb_(x)Te_(3))is commonly used for thermoelectric generation at temperatures near ambient temperature.Here,we report incorporating reduced graphene oxide(rGO)and Cu_(2)Se_(0.98)Te_(0.02) into the Bi_(0.5)Sb_(1.5)Te_(3)(BST)(rGO/Bi_(0.5)Sb_(1.5)Te_(3-x)Cu_(2)Se_(0.98)Te_(0.02),where x=0.0%,0.1%,0.3%,0.5% and 1.0%,in mass)synthesized by a solid-state technique.The dispersion of rGO and Cu_(2)Se_(0.98)Te_(0.02) into the BST matrix improved carrier transport properties at the grain boundary interfaces and reduced thermal conductivity.Strong electron scattering at large interface barriers was responsible for increased electrical conductivity.The bulk sample of rGO/BST-0.3%Cu_(2)Se_(0.98)Te_(0.02)(in mass)possessed a low thermal conductivity of 0.76 W·m^(−1)·K^(−1) at 497 K.Enhanced phonon scattering at grain boundaries between BST and rGO/Cu_(2)Se_(0.98)Te_(0.02) caused a low thermal conductivity.At 448 K,the highest zT value for rGO/BST-0.3% Cu_(2)Se_(0.98)Te_(0.02)(in mass)was 1.64,which is 37% higher than the zT value for pure BST(zT=1.19).Results suggested that incorporating rGO and Cu_(2)Se_(0.98)Te_(0.02) into the BST matrix effectively improved thermoelectric power generation.展开更多
Bi(Te,Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric(TE)materials due to their high performance at near room tem-perature.Compared...Bi(Te,Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric(TE)materials due to their high performance at near room tem-perature.Compared with 3D bulks,2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro-and nano-devices.For device applications,high average TE performance over the entire operating temperature range is critical.Herein,highly c-axis-oriented N-type Bi(Te,Se)epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature.The film deposited at~260℃demonstrate a remarkable average power factor(PFave)of~24.4 mW·cm^(-1)·K^(-2)over the tem-perature range of 305e470 K,higher than most of the state-of-the-art Bi(Te,Se)-based films.Moreover,the estimated average zT value of the film is as high as~0.81.We then constructed thin-film TE devices by using the above oriented Bi(Te,Se)films,and the maximum output power density of the device can reach up to~30.1 W/m^(2)under the temperature difference of 40 K.Predictably,the outstanding average TE performance of the highly oriented Bi(Te,Se)thin films will have an excellent panorama of applications in semiconductor cooling and power generation.展开更多
Bi2Te3-based alloys are the most mature commercial thermoelectric(TE)materials for the cooling application near room temperature.However,the poor mechanical properties of the commercial zone melting(ZM)ingot severely ...Bi2Te3-based alloys are the most mature commercial thermoelectric(TE)materials for the cooling application near room temperature.However,the poor mechanical properties of the commercial zone melting(ZM)ingot severely limits the further application.Meanwhile,due to the donor-like effect,the robust polycrystalline n-type bulks usually have low TE performance near room temperature.Herein,based on the commercial ZM ingots,a high figure of merit(zT)of 1.0 at 320 K and good mechanical properties are achieved via the hot extrusion.The dynamic recrystallization in the hot-extrusion process can suppress the donor-like effect and refine the large ZM grains into fine-equiaxed grains.Moreover,the obtained polycrystalline Bi2Te2.79Se0.21 has good preferential orientation and high carrier mobility(m).The high m and the weaken donor-like effect maintain the high power factor(PF)of 43.1 mW cm^(-1)K^(-2)in the hot-extruded ZM sample.Due to the enhanced phonon scattering,the total thermal conductivity ktot decreased to 1.35 W·m^(-1)·K^(-1).To demonstrate the good mechanical properties of the extruded ZM sample,micro TE dices with the cross sections of 300μm×300 mm and 200μm×200 mm are successfully cut from the extrusion sample.This study provided a fast and low-cost extrusion technique to improve the TE and mechanical properties of the commercial ZM ingot at room temperature.展开更多
Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high F...Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high Faradaic efficiency(FE)due to the extremely strong N≡N bonds and the competing hydrogen evolution reaction(HER).Recently,bismuth telluride(Bi_(2)Te_(3))with two-dimensional layered structure has been reported as a promising catalyst for N_(2)fixation.Herein,to further enhance its NRR activity,a general doping strategy is developed to introduce and modulate the crystal defects of Bi_(2)Te_(3)nanosheets by adjusting the amount of Ce dopant(denoted as Ce_(x)-Bi_(2)Te_(3),where x represents the designed molar ratio of Ce/Bi).Meanwhile,the crystal defects can be designed and controlled by means of ion substitution and charge compensation.At−0.60 V versus the reversible hydrogen electrode(RHE),Ce_(0.3)-Bi_(2)Te_(3)exhibits a high NH_(3) yield(78.2μg·h^(−1)·mgcat^(−1)),a high FE(19.3%),excellent structural and electrochemical stability.Its outstanding catalytic activity is attributed to the tunable crystal defects by Ce doping.This work not only contributes to enhancing the NRR activity of Bi_(2)Te_(3)nanosheets,but also provides a reliable approach to prepare high-performance electrocatalysts by controlling the type and concentration of crystal defects for artificial N_(2)fixation.展开更多
For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chie...For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chief approach to improve their thermoelectric performance. Herein, we report the multiple effects of Se doping on thermoelectric performance of p-type Bi0.5Sb1,5Te3-xSex ＋ 3 wt% Te ZM ingots, which increases carrier concentration, reduces lattice thermal conductivity and deteriorates the carrier mobility. As a result, the peak figure of merit （ZT） is shifted to a higher temperature and a high ZT 1.2 at 350 K is obtained, due to the reduced thermal conductivity and suppressed intrinsic conduction. Further, decreasing Sb content is followed to optimize the room temperature performance and a ZT - 1.1 at 300 K is obtained. These results are significant for designing and optimizing the thermoelectric performance of commercial Bi0.5Sb1.5Te3＋ 3 wt% Te ZM alloys.展开更多
N-type Se&Lu-codoped Bi2Te3 nanopowders were prepared by hydrothermal method and sintered by spark plasma sintering technology to form dense samples.By further doping Se element into Lu-doped Bi2Te3 samples,the th...N-type Se&Lu-codoped Bi2Te3 nanopowders were prepared by hydrothermal method and sintered by spark plasma sintering technology to form dense samples.By further doping Se element into Lu-doped Bi2Te3 samples,the thickness of the nanosheets has the tendency to become thinner.The electrical conductivity of Lu0.1Bi1.9Te3−xSex material is reduced with the increasing Se content due to the reduced carrier concentration,while the Seeback coefficient values are enhanced.The lattice thermal conductivity of the Lu0.1Bi1.9Te3−xSex is greatly reduced due to the introduced point defects and atomic mass fluctuation.Finally,the Lu0.1Bi1.9Te2.7Se0.3 sample obtained a maximum ZT value of 0.85 at 420 K.This study provides a low-cost and simple low-temperature method to mass production of Se&Lu-codoped Bi2Te3 with high thermoelectric performance for practical applications.展开更多
We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition(CVD).It is found that the population of bulk carriers ca...We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition(CVD).It is found that the population of bulk carriers can be suppressed effectively with increasing the Se concentration x.In Bi2(Te1−xSex)3 nanowires with x=25%±5%,the ambipolar surface conduction associated with tuning the Fermi energy across the Dirac point of topological surface states is induced by applying a back-gate voltage.Importantly,we find that while the magnetoresistance(MR)follows the weak antilocalization(WAL)behavior when the Fermi level is tuned away from the Dirac point,MR is enhanced in magnitude and turns more linear in the whole magnetic field range(between±9 T)near the Dirac point.The observation of the enhanced linear magneto-resistance(LMR)and crossover from WAL to LMR,near the Dirac point provides a deeper insight into understanding the nature of topological insulator’s surface transport and the relation between these two widely observed magneto-transport phenomena.展开更多
Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spect...Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spectroscopy （AES）. We find that the surface of relatively thick （more than tens of nanometers） Bi2Te3 NPs is oxidized in the air and forms a bump under heating with moderate laser power, as revealed by the emergence of Raman lines characteristic of Bi2O3 and TeO2 and characterization by AFM and EDS. Further increase of laser power burns holes on the surface of the NPs. Thin （thicknesses less than 20 nm） NPs with stoichiometry different from Bi2Te3 were also studied. Raman lines from non-stoichiometric NPs are different from those of stoichiometric ones and display characteristic changes with the increase of Bi concentration. Thin NPs with the same thickness but different stoichiometries show different color contrast compared to the substrate in the optical image. This indicates that the optical absorption coefficient in thin Bi-Te NPs strongly depends on their stoichiometry.展开更多
Bismuth-telluride-based alloys are the best thermoelectric materials used in commercial solid-state refrigeration near room temperature.Nevertheless,for n-type polycrystalline alloys,their thermoelectric figure of mer...Bismuth-telluride-based alloys are the best thermoelectric materials used in commercial solid-state refrigeration near room temperature.Nevertheless,for n-type polycrystalline alloys,their thermoelectric figure of merit(zT) values at room temperature are often less than1.0,due to the high electron concentration originating from the donor-like effect induced by the mechanical deformation process.Herein,carrier concentration for better performance near room temperature was optimized through manipulating intrinsic point defects by sulfur alloying.Sulfur alloying significantly decreases antisite defects concentration and suppresses donor-like effect,resulting in optimized carrier concentration and reduced electronic thermal conductivity.The hot deformation process was also applied to improve carrier mobility due to the enhanced texture.As a result,a high zT value of 1 at 300 K and peak zT value of 1.1 at 350 K were obtained for the twice hot-deformed Bi_(2) Te_(2.7)Se_(0.21)S_(0.09) sample,which verifies sulfur alloying is an effective method to improve thermoelectric performance of n-type polycrystalline Bi2 Te3-based alloys near room temperature.展开更多
Bismuth teUuride （Bi2Te3） is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their ap...Bismuth teUuride （Bi2Te3） is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their application in nanoelectronics. Determination of the fracture toughness plays a crucial role for the potential application of topological insulators in flexible electronics and nanoelectro- mechanical devices. Using depth-sensing nanoindentation tests, we investigated for the first time the fracture toughness of bulk single crystals of Bi2Te3 topological insulators, grown using the Bridgmantockbarger method. Our results highlight one of the possible pitfalls of the technology based on topological insulators.展开更多
基金supported by the National Natural Science Foundation of China(No.50731006)
文摘A new basic electrolyte with two cationic plating additives, polydiaminourea and polyaminosulfone, was investigated for the electrochemical deposition of the bismuth telluride film on a nickel-plated copper foil. Tellurium starts to deposit at a higher potential （-0.35 V） than bismuth （-0.5 V） in this electrolyte. The tellurium-to-bismuth ratio increases while the deposition potential declines from -1 to -1.25 V, indicating a kinetically quicker bismuth deposition at higher potentials. The as-deposited film features good adhesion to the substrate and smooth morphology, and has a nearly amorphous crystal structure disclosed by X-ray diffraction patterns.
基金supported by the National Natural Science Foundation of China under Grant Nos.92163211,52002137,51872102,and 51802070the Fundamental Research Funds for the Central Universities under Grant Nos.2021XXJS008 and 2018KFYXKJC002Graduates’Innovation Fund,Huazhong University of Science and Technology under Grant No.2020yjs CXCY022
文摘Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply.It is noted that thermoelectric power generators are easy to damage in the dynamic service process,resulting in the formation of microcracks and performance degradation.Herein,we prepare a new hybrid hydrogel thermoelectric material PAAc/XG/Bi_(2)Se_(0.3)Te_(2.7)by an in situ polymerization method,which shows a high stretchable and self-healable performance,as well as a good thermoelectric performance.For the sample with Bi_(2)Se_(0.3)Te_(2.7)content of 1.5 wt%(i.e.,PAAc/XG/Bi2Se0.3Te27(1.5 wt%)),which has a room temperature Seebeck coefficient of-0.45 mV K^(-1),and exhibits an open-circuit voltage of-17.91 mV and output power of 38.1 nW at a temperature difference of 40 K.After being completely cut off,the hybrid thermoelectric hydrogel automatically recovers its electrical characteristics within a response time of 2.0 s,and the healed hydrogel remains more than 99%of its initial power output.Such stretchable and self-healable hybrid hydrogel thermoelectric materials show promising potential for application in dynamic service conditions,such as wearable electronics.
基金This work was supported by the National Natural Science Foundation of China(11574267,51571177 and 61534001)the National Natural Science Fund for Distinguished Young Scholars(51725102).
文摘Bismuth telluride-based alloys are the most widely used commercial thermoelectric(TE)material for room temperature refrigeration.Here,we successfully shift up the optimum figure of merit of n-type bismuth-telluride-based TE materials for mid-temperature power generation.SbI_(3)doping is used to regulate the carrier concentration and Indium alloying to increase the bandgap,suppressing the detrimental bipolar conduction in the mid-temperature range.The lattice thermal conductivity is significantly reduced due to the multiscale microstructures induced via hot deformation.As a result,a peak zT of~1.1 was attained at 625 K for Bi_(1.85)In_(0.15)Te_(2)Se+0.25 wt%SbI_(3)alloy after hot deformation,showing a great application prospect of this alloy in mid-temperature TE power generation.
文摘Thin films of Bismuth Telluride (Bi<sub>2</sub>Te<sub>3</sub>) are prepared by thermal evaporation from nanopowders on the glass substrates. The XRD patterns of films show that all the films are polycrystalline and the crystalline increased by annealing temperature. Measuring of the thermoelectric power of thin films in the temperature range 300 to 380 K shows that Seebeck Coefficients have both negative and positive values, indicating that the films have both n-type and p-type conductivity. The re-crystallization of films is done by annealing from 130°C to 175°C and Seebeck Coefficient varied from -150 to 100 μV/K.
基金Funded by Open Foundation of State Key Laboratory of Ad-vanced Technology for Materials Synthesis and Processing, Wuhan University of Technology.
文摘The density junction theory and discrete variation method ( DFT - DVM) was used to study correlation between composition, structure, chemical bond, and property of thermoelectrics of Bi-Sb-Te series. 8 models of Bi20-xSbxTe32(x = 0,2,6,8,12,14,18 and 20) were calculated. The results show that there is less difference in the ionic bonds between Te( I)-Bi(Sb) and Te(Ⅱ)-Bi(Sb) , but the covalent bond of Te(Ⅰ)-Bi( Sb ) is stronger than that of Te(Ⅱ)-Bi( Sb ) . The interaction between Te(Ⅰ) and Te(Ⅰ) in different layers is the weakest and the interaction should be Van Der Wools power. The charge of Sb is lower than that of Bi, and the ionic bond of Te-Sb is weaker than that of Te-Bi. The covalent bond of Te-Sb is also weaker than that of Te-Bi. Therefore, the thermoelectric property may be imfiroved by adjusting the electrical conductivity and thermal conductivity through changing the composition in the compounds of Bi-Sb-Te. The calculated results are consistent with the experiments.
基金Funded by the Major International Cooperation Programof Na-tional Science Foundation of China (No.50310353)
文摘A kind of p-type segmented Bi2 Te3/CoSB3 thermoetectric material was preparea oy sparse ptasma sintering（ SPS ） . When the segmented materials were used at the temperature ranging from 300 K to 800 K, the junction temperature was optimized, which is about 500 K, and the corresponding length ratio of CoSb3 to Bi2 Te3 is about 15 ： 2. The measured maximum power output of segmented materials is abont 320 W·m^-2, which is about 1.8 times as high as that of monolithic material CoSb3 under the same measuring conditions.
基金R.K.C.acknowledges grant#NSF(DMR-1508420).Y.W.thanks the support from the Herbert L.Stiles Professorship and ACRI Center IrHtiative from Iowa State University.
文摘Anisotropy and inhomogeneity are ubiquitous in spark plasma sintered thermoelectric devices.However,the origin of inhomogeneity in thermoelectric nanocomposites has rarely been investigated so far.Herein,we systematically study the impact of inhomogeneity in spark plasma sintered bismuth antimony telluride(BiSbTe)thermoelectric nanocomposites fabricated from solution-synthesized nanoplates.The figure of merit can reach 1.18,which,however,can be overestimated to 1.88 without considering the inhomogeneity.Our study reveals that the inhomogeneity in thermoelectric properties is attributed to the non-uniformity of porosity,textures and elemental distribution from electron backscatter diffraction and energy-dispersive spectroscopy characterizations.This finding suggests that the optimization of bulk material homogeneity should also be actively pursued in any future thermoelectric material research.
基金This work was financially supported by the National Key Project on Basic Research of China (No.ZM200103A01)
文摘Bi2-xSbxTe3 thermoelectric films were electrochemically deposited from the solution containing Bi^3＋, HTeO2^＋and SbO^＋. ESEM （environmental scanning electron microscope） investigations indicated that the crystalline state of Bi2-xSbxTe3 films transformed from equiaxed crystal to dendritic crystal with the negative shift of deposition potential. XRD and EDS were used to characterize the structure and composition of the electrodeposited films. The Seebeck coefficient and the temperature dependence of the resistance of Bi2-xSbxTe3 films were measured. The results showed that the composition of the film electrodeposited at -0.5 V is Bi2-xSbxTe3 with the largest Seebeck coefficient of 213 μV·K^-1.
基金supported by the U.S.Department of Energy,Office of Science and Office of Basic Energy Sciences under award number DE-SC0014520the EPIC facility of Northwestern University’s NUANCE Center,support from the Soft and Hybrid Nanotechnology Experimental(SHyNE)Resource(NSF ECCS-1542205)+5 种基金the MRSEC Program(NSF DMR-1720139)at the Materials Research Centerthe International Institute for Nanotechnology(IIN)the Keck Foundationthe State of Illinois,through the IINthe MatCI Facility which receives support from the MRSEC Program(NSF DMR-1720139)of the Materials Research Center at Northwestern Universitysupported by the National Science Foundation Graduate Research Fellowship under Grant No.DGE-1324585.
文摘Alloys of Bi_(2)Te_(3) and Sb_(2)Te_(3) are the best performing p-type thermoelectrics near room temperature and have been the subject of extensive engineering efforts.Dramatic improvement is achieved by introducing defects that effectively scatter phonons and reduce thermal conductivity.Unfortunately,outstanding results are often difficult to reproduce as the process variables involved are difficult to control or possibly unknown.Here,a reproducible and controllable method of fabricating porous Bi_(0.5)Sb_(1.5)Te_(3+x) is presented.While effective medium theory(EMT)predicts no benefit,improvements in the thermoelectric quality factor,B(which determines the maximum zT of a materials),were as high as 45% parallel to the pressing direction for a sample of roughly 20% porosity.The study of microstructural evolution with increasing porosity is facilitated by a combination of Scanning/Transmission Electron Microscopy(S/TEM)and Electron Backscattered Diffraction(EBSD).This study reveals a statistically significant shift in the distribution of grain boundaries favoring lower energy twins,which coincides with an increase in the presence of stepped twin boundaries.This work demonstrates the potential benefits of careful grain boundary engineering and the need for further detailed studies of the dependence of thermal and electrical transport on grain boundary structure and orientation in these alloys.
基金This research has received funding support from the National Science,Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation[grant number B05F640150],Thailand.
文摘Bismuth antimony telluride(Bi_(2–x)Sb_(x)Te_(3))is commonly used for thermoelectric generation at temperatures near ambient temperature.Here,we report incorporating reduced graphene oxide(rGO)and Cu_(2)Se_(0.98)Te_(0.02) into the Bi_(0.5)Sb_(1.5)Te_(3)(BST)(rGO/Bi_(0.5)Sb_(1.5)Te_(3-x)Cu_(2)Se_(0.98)Te_(0.02),where x=0.0%,0.1%,0.3%,0.5% and 1.0%,in mass)synthesized by a solid-state technique.The dispersion of rGO and Cu_(2)Se_(0.98)Te_(0.02) into the BST matrix improved carrier transport properties at the grain boundary interfaces and reduced thermal conductivity.Strong electron scattering at large interface barriers was responsible for increased electrical conductivity.The bulk sample of rGO/BST-0.3%Cu_(2)Se_(0.98)Te_(0.02)(in mass)possessed a low thermal conductivity of 0.76 W·m^(−1)·K^(−1) at 497 K.Enhanced phonon scattering at grain boundaries between BST and rGO/Cu_(2)Se_(0.98)Te_(0.02) caused a low thermal conductivity.At 448 K,the highest zT value for rGO/BST-0.3% Cu_(2)Se_(0.98)Te_(0.02)(in mass)was 1.64,which is 37% higher than the zT value for pure BST(zT=1.19).Results suggested that incorporating rGO and Cu_(2)Se_(0.98)Te_(0.02) into the BST matrix effectively improved thermoelectric power generation.
基金supported by the National Natural Science Foundation of China(51972094)Hebei Provincial Department of Science and Technology(206Z4403G)+1 种基金Innovation Team Project of Hebei University(No.150000321008,521201623004)supported in part by the Microanalysis Center and the High-Performance Computing Center of Hebei University.
文摘Bi(Te,Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric(TE)materials due to their high performance at near room tem-perature.Compared with 3D bulks,2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro-and nano-devices.For device applications,high average TE performance over the entire operating temperature range is critical.Herein,highly c-axis-oriented N-type Bi(Te,Se)epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature.The film deposited at~260℃demonstrate a remarkable average power factor(PFave)of~24.4 mW·cm^(-1)·K^(-2)over the tem-perature range of 305e470 K,higher than most of the state-of-the-art Bi(Te,Se)-based films.Moreover,the estimated average zT value of the film is as high as~0.81.We then constructed thin-film TE devices by using the above oriented Bi(Te,Se)films,and the maximum output power density of the device can reach up to~30.1 W/m^(2)under the temperature difference of 40 K.Predictably,the outstanding average TE performance of the highly oriented Bi(Te,Se)thin films will have an excellent panorama of applications in semiconductor cooling and power generation.
基金supported by the National Nature Science Foundation of China(U1738114)the China Postdoctoral Science Foundation(2020TQ0330 and 2021M703331).
文摘Bi2Te3-based alloys are the most mature commercial thermoelectric(TE)materials for the cooling application near room temperature.However,the poor mechanical properties of the commercial zone melting(ZM)ingot severely limits the further application.Meanwhile,due to the donor-like effect,the robust polycrystalline n-type bulks usually have low TE performance near room temperature.Herein,based on the commercial ZM ingots,a high figure of merit(zT)of 1.0 at 320 K and good mechanical properties are achieved via the hot extrusion.The dynamic recrystallization in the hot-extrusion process can suppress the donor-like effect and refine the large ZM grains into fine-equiaxed grains.Moreover,the obtained polycrystalline Bi2Te2.79Se0.21 has good preferential orientation and high carrier mobility(m).The high m and the weaken donor-like effect maintain the high power factor(PF)of 43.1 mW cm^(-1)K^(-2)in the hot-extruded ZM sample.Due to the enhanced phonon scattering,the total thermal conductivity ktot decreased to 1.35 W·m^(-1)·K^(-1).To demonstrate the good mechanical properties of the extruded ZM sample,micro TE dices with the cross sections of 300μm×300 mm and 200μm×200 mm are successfully cut from the extrusion sample.This study provided a fast and low-cost extrusion technique to improve the TE and mechanical properties of the commercial ZM ingot at room temperature.
基金supported by the National Natural Science Foundation of China(52162029)Yunnan Provincial Natural Science Key Fund(202101AS070015)+1 种基金the National Key R&D Program of China(2022YFF0503804)the Outstanding Youth Fund of Yunnan Province(202201AV070005)。
基金the National Natural Science Foundation of China(Nos.22074137 and 21721003).
文摘Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high Faradaic efficiency(FE)due to the extremely strong N≡N bonds and the competing hydrogen evolution reaction(HER).Recently,bismuth telluride(Bi_(2)Te_(3))with two-dimensional layered structure has been reported as a promising catalyst for N_(2)fixation.Herein,to further enhance its NRR activity,a general doping strategy is developed to introduce and modulate the crystal defects of Bi_(2)Te_(3)nanosheets by adjusting the amount of Ce dopant(denoted as Ce_(x)-Bi_(2)Te_(3),where x represents the designed molar ratio of Ce/Bi).Meanwhile,the crystal defects can be designed and controlled by means of ion substitution and charge compensation.At−0.60 V versus the reversible hydrogen electrode(RHE),Ce_(0.3)-Bi_(2)Te_(3)exhibits a high NH_(3) yield(78.2μg·h^(−1)·mgcat^(−1)),a high FE(19.3%),excellent structural and electrochemical stability.Its outstanding catalytic activity is attributed to the tunable crystal defects by Ce doping.This work not only contributes to enhancing the NRR activity of Bi_(2)Te_(3)nanosheets,but also provides a reliable approach to prepare high-performance electrocatalysts by controlling the type and concentration of crystal defects for artificial N_(2)fixation.
基金supported by the National Natural Science Foundation of China (Nos. 61534001 and 11574267)the National Science Fund for Distinguished Young Scholars (No.51725102)
文摘For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chief approach to improve their thermoelectric performance. Herein, we report the multiple effects of Se doping on thermoelectric performance of p-type Bi0.5Sb1,5Te3-xSex ＋ 3 wt% Te ZM ingots, which increases carrier concentration, reduces lattice thermal conductivity and deteriorates the carrier mobility. As a result, the peak figure of merit （ZT） is shifted to a higher temperature and a high ZT 1.2 at 350 K is obtained, due to the reduced thermal conductivity and suppressed intrinsic conduction. Further, decreasing Sb content is followed to optimize the room temperature performance and a ZT - 1.1 at 300 K is obtained. These results are significant for designing and optimizing the thermoelectric performance of commercial Bi0.5Sb1.5Te3＋ 3 wt% Te ZM alloys.
基金This work was funded by the Fundamental Research Funds for the Central Universities(No.2232020A-02)National Natural Science Foundation of China(Nos.51774096,51871053,51902333)+3 种基金Shanghai Committee of Science and Technology(18JC1411200)Program for Innovative Research Team in University of Ministry of Education of China(IRT_16R13)Q.Zhang acknowledges financial support sponsored by Shanghai Saiiling Program(19YF1454000)Key Research Program of Frontier Sciences,CAS(Grant No.ZDBS-LY-JSC037).
文摘N-type Se&Lu-codoped Bi2Te3 nanopowders were prepared by hydrothermal method and sintered by spark plasma sintering technology to form dense samples.By further doping Se element into Lu-doped Bi2Te3 samples,the thickness of the nanosheets has the tendency to become thinner.The electrical conductivity of Lu0.1Bi1.9Te3−xSex material is reduced with the increasing Se content due to the reduced carrier concentration,while the Seeback coefficient values are enhanced.The lattice thermal conductivity of the Lu0.1Bi1.9Te3−xSex is greatly reduced due to the introduced point defects and atomic mass fluctuation.Finally,the Lu0.1Bi1.9Te2.7Se0.3 sample obtained a maximum ZT value of 0.85 at 420 K.This study provides a low-cost and simple low-temperature method to mass production of Se&Lu-codoped Bi2Te3 with high thermoelectric performance for practical applications.
基金supported by the National Natural Science Foundation of China(No.51971220)the National Basic Research Program of China(No.2017YFA0206302).X.P.A.G.thanks the National Science Foundation for its financial support under Award DMR-1607631.
文摘We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition(CVD).It is found that the population of bulk carriers can be suppressed effectively with increasing the Se concentration x.In Bi2(Te1−xSex)3 nanowires with x=25%±5%,the ambipolar surface conduction associated with tuning the Fermi energy across the Dirac point of topological surface states is induced by applying a back-gate voltage.Importantly,we find that while the magnetoresistance(MR)follows the weak antilocalization(WAL)behavior when the Fermi level is tuned away from the Dirac point,MR is enhanced in magnitude and turns more linear in the whole magnetic field range(between±9 T)near the Dirac point.The observation of the enhanced linear magneto-resistance(LMR)and crossover from WAL to LMR,near the Dirac point provides a deeper insight into understanding the nature of topological insulator’s surface transport and the relation between these two widely observed magneto-transport phenomena.
文摘Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spectroscopy （AES）. We find that the surface of relatively thick （more than tens of nanometers） Bi2Te3 NPs is oxidized in the air and forms a bump under heating with moderate laser power, as revealed by the emergence of Raman lines characteristic of Bi2O3 and TeO2 and characterization by AFM and EDS. Further increase of laser power burns holes on the surface of the NPs. Thin （thicknesses less than 20 nm） NPs with stoichiometry different from Bi2Te3 were also studied. Raman lines from non-stoichiometric NPs are different from those of stoichiometric ones and display characteristic changes with the increase of Bi concentration. Thin NPs with the same thickness but different stoichiometries show different color contrast compared to the substrate in the optical image. This indicates that the optical absorption coefficient in thin Bi-Te NPs strongly depends on their stoichiometry.
基金financially supported by the National Key Research and Development Program of China(No.2019YFA0704902)the National Natural Science Foundation of China(Nos.51871199 and 61534001)。
文摘Bismuth-telluride-based alloys are the best thermoelectric materials used in commercial solid-state refrigeration near room temperature.Nevertheless,for n-type polycrystalline alloys,their thermoelectric figure of merit(zT) values at room temperature are often less than1.0,due to the high electron concentration originating from the donor-like effect induced by the mechanical deformation process.Herein,carrier concentration for better performance near room temperature was optimized through manipulating intrinsic point defects by sulfur alloying.Sulfur alloying significantly decreases antisite defects concentration and suppresses donor-like effect,resulting in optimized carrier concentration and reduced electronic thermal conductivity.The hot deformation process was also applied to improve carrier mobility due to the enhanced texture.As a result,a high zT value of 1 at 300 K and peak zT value of 1.1 at 350 K were obtained for the twice hot-deformed Bi_(2) Te_(2.7)Se_(0.21)S_(0.09) sample,which verifies sulfur alloying is an effective method to improve thermoelectric performance of n-type polycrystalline Bi2 Te3-based alloys near room temperature.
文摘Bismuth teUuride （Bi2Te3） is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their application in nanoelectronics. Determination of the fracture toughness plays a crucial role for the potential application of topological insulators in flexible electronics and nanoelectro- mechanical devices. Using depth-sensing nanoindentation tests, we investigated for the first time the fracture toughness of bulk single crystals of Bi2Te3 topological insulators, grown using the Bridgmantockbarger method. Our results highlight one of the possible pitfalls of the technology based on topological insulators.
