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The contact resistivity originating from the metal–semiconductor interface is a crucial factor for conversion efficiency of thermoelectric films devices. Due to anisotropic nature of state‐of‐art Bi2Te3 films, the contact resistivity also needs to match with the different orientations in/out‐plane film configurations. Here, a series of bismuth telluride (Bi2Te3) films with different orientations are deposited, and the contact resistivity between Ti/Cr/Cu and Bi2Te3‐based films is studied in detail. The increased (00l) orientation can effectively reduce the contact resistivity mainly due to the enhanced Tunneling effect. Finally, a low contact resistivity of 0.84 µΩ cm2 is observed in highly (00l)‐orientated Bi2Te3 film in contact with Cr. This work provides an effective method to control contact resistivity by adjusting the orientation of film, and also provides guidance on how to further improve the performance of thin film‐TEDs with different configurations. [ABSTRACT FROM AUTHOR]

Mg2Sn is a promising medium-temperature thermoelectric material due to its superior performance and non-toxic, low-cost nature. Because of the divergence of band effective mass and degeneracy between the conduction and valence band, Mg2Sn is also promising to achieve superior performance near room temperature. To realize the desired bandgap and optimal carrier concentration, in this work, Mg2Pb is alloyed to reduce the bandgap of Mg2Sn, and Bi is adopted for carrier concentration optimization. Alloying with Mg2Pb makes the bandgap gradually tuned, and with the increase in carrier concentration, more conduction band valleys are involved for electronic transport as the Fermi level goes deeper. Besides, the phonon scattering is simultaneously enhanced because of the introduced large number of defects. Finally, a power factor as high as 52 μW cm−1 K−2 at 400 K, and 42 μW cm−1 K−2 at room temperature is obtained in this work, and the peak zT value for the Mg2.03Sn0.734Pb0.25Bi0.016 sample reaches 0.8 at 500 K, the average figure of merit is zTave ∼ 0.6 within the temperature range of 300–550 K, surpassing many Mg2Sn based materials near room temperature. The thermoelectric figure of merit can achieve a higher value if the lattice thermal conductivity is further reduced, which demonstrates that Mg2Sn is promising for near room temperature applications. [ABSTRACT FROM AUTHOR]

Bi1−xSbx crystal is one of the best n-type thermoelectric materials below 200 K, but its weak mechanical strength hinders practical applications for deep refrigeration. Herein, we adopted the mechanical enhancement method of hot extrusion to investigate the comprehensive mechanical and thermoelectric properties of Bi0.905Sb0.095. It revealed that reducing the grain size of the matrix and increasing the extrusion ratio can improve the gain size uniformity and mechanical properties. Meanwhile, the thermoelectric performance depends on the texture, grain size, and local composition. The extruded sample prepared by ingot with the high extrusion ratio of 9:1 generated uniform small grains, which resulted in the high bending strength of Bi1−xSbx~130 Mpa and a high power factor of ~68 μW·cm−1·K−2@173 K, as well as the relatively high figure of merit of 0.25@173K. This work highlights the importance of the uniform distribution of the grain size and the compositions for Bi1−xSbx, as well as the required universal key parameter for the hot extrusion method. [ABSTRACT FROM AUTHOR]

α-MgAgSb is taken as the p-type leg material for recently focused Mg-based thermoelectric devices because of the high thermoelectric performance near room temperature. However, the thermoelectric performance of α-MgAgSb is inhibited by the existence of the Ag-rich second phase. The ordinary methods like carrier concentration optimization and minimizing lattice thermal conductivity were nearly invalid because of the extremely low doping level for heteroatoms and intrinsically low lattice thermal conductivity. The crystal structure of α-MgAgSb can be viewed as Ag atom filled in half distorted hexahedron in the distorted rock salt skeleton formed by the Mg–Sb sublattice. In this work, by replacing the smaller Mg in the sublattice with Pb, the volume of the distorted hexahedron is effectively expanded to accommodate Ag atoms and then lead to the re-dissolution of Ag-rich second phase in the matrix. In addition, as Ag is the main source of low-frequency phonons, the enhanced lattice anharmonicity by Pb doping leads to stronger scattering of phonons in the distorted hexahedron and results in 20% reduction of lattice thermal conductivity in the temperature range of 300–500 K. Finally, the figure of merit zT is enhanced by ∼40% in the whole temperature range, demonstrating that lattice management is a promising method for the optimization of α-MgAgSb materials. [ABSTRACT FROM AUTHOR]

At present, the weak thermoelectric and mechanical performance of zone‐melting bismuth telluride alloys cannot support the further improvement of cooling and processing performance of semiconductor refrigeration devices. Here, MnO2 is added into high‐strength Bi0.4Sb1.6Te3 prepared by ball milling method to optimize its thermoelectric transport properties. Via in situ reaction, Sb2O3 nano‐precipitates are formed in the matrix, which also leads to the surplus of Te element. As results, the donor‐like effect is suppressed, thereby increasing carrier concentration and power factor. Besides, volatilization of Te‐rich phases during sintering leaves plentiful nanopores, which together with Sb2O3 nano‐precipitates significantly decrease the lattice thermal conductivity. Eventually, the maximum ZT reaches 1.43 at 75 °C for the Bi0.4Sb1.6Te3+0.01MnO2 sample. On this basis, a 31‐pairs module made of the material and commercial n‐type BiTeSe produces large temperature differences (ΔT) of 70.1, 80.8, and 89.4 K at the hot‐side temperature (Th) of 300, 325, and 350 K respectively, which are highly competitive. The maximum coefficient of performance of 8.6 and cooling capacity of 7 W are achieved when Th is set as 325 K. This excellent progress will promote the further development of bismuth telluride refrigeration modules. [ABSTRACT FROM AUTHOR]

The different masses, ionic radii, and chemical valences of the nonequivalent crystallographic sites of thermoelectric (TE) compounds provide an effective way to modulate the thermoelectric performance by selective substitution. In this work, the selective substitution of In+ by Pb for the binary InTe material monotonically reduces the carrier concentration, which is greatly beneficial to the mechanism investigation of serious grain boundary scattering (GBS). This is the first time this point has been mentioned with regard to InTe material. As a result, we found that GBS was dominated by the grain size when the carrier concentration was higher than 0.7 × 1019 cm−3 but was inversely governed by the carrier concentration when the carrier was situated at a lower density. In particular, the occupation of Pb on the targeted In+ site could further reduce the lattice thermal conductivity. Finally, In0.9999Pb0.0001Te achieved the improved power factor and average zT value, which could contribute to high-power generation below a medium temperature. This effect of increasing the carrier concentration on the suppression of GBS sheds light on the possibility of improving electron mobility by increasing the carrier concentration. [ABSTRACT FROM AUTHOR]

Traffic anomaly detection is an essential part of an intelligent transportation system. Automatic traffic anomaly detection can provide sufficient decision-support information for road network operators, travelers, and other stakeholders. This research proposes a novel automatic traffic anomaly detection method based on spatial-temporal graph neural network representation learning. We divide traffic anomaly detection into two steps: first is learning the implicit graph feature representation of multivariate time series of traffic flows based on a graph attention model to predict the traffic states. Second, traffic anomalies are detected using graph deviation score calculation to compare the deviation of predicted traffic states with the observed traffic states. Experiments on real network datasets show that with an end-to-end workflow and spatial-temporal representation of traffic states, this method can detect traffic anomalies accurately and automatically and achieves better performance over baselines. [ABSTRACT FROM AUTHOR]

La3Te4-based rare-earth telluride is a kind of n-type high-temperature thermoelectric (TE) material with an operational temperature of up to 1273 K, which is a promising candidate for thermoelectric generators. In this work, the Sm substitution in La3−xSmxTe4/Ni composites is reported. The electrical transport property of La3−xSmxTe4 is modified by reducing carrier concentration due to the substitution of Sm2+ for La3+. The electric thermal conductivity decreases by 90% due to carrier concentration reduction, which mainly contributes to a reduction in total thermal conductivity. Lattice thermal conductivity also decreases by point-defect scattering by Sm doping. Meanwhile, based on our previous study, compositing nickel improves the thermal stability of the La3 − xSmxTe4 matrix. Finally, combined with carrier concentration optimization and the decreased thermal conductivity, a maximum zT of 1.1 at 1273 K and an average zTave value of 0.8 over 600 K–1273 K were achieved in La2.315Sm0.685Te4/10 vol.% Ni composite, which is among the highest TE performance reported in La3Te4 compounds. [ABSTRACT FROM AUTHOR]

Summary: Waste heat recovery helps reduce energy consumption, decreases carbon emissions, and enhances sustainable energy development. In China, energy‐intensive industries dominate the industrial sector and have significant potential for waste heat recovery. We propose a novel waste heat recovery system assisted by a heat pipe and thermoelectric generator (TEG) namely, heat pipe TEG (HPTEG)，to simultaneously recover waste heat and achieve electricity generation. Moreover, the HPTEG provides a good approach to bridging the mismatch between energy supply and demand. Based on the technical reserve on high‐temperature heat pipe manufacturing and TEG device integration, a laboratory‐scale HPTEG prototype was established to investigate the coupling performances of the heat pipes and TEGs. Static energy conversion and passive thermal transport were achieved with the assistance of skutterudite TEGs and potassium heat pipes. Based on the HPTEG prototype, the heat transfer and the thermoelectric conversion performances were investigated. Potassium heat pipes exhibited excellent heat transfer performance with 95% thermal efficiency. The isothermality of such a heat pipe was excellent, and the heat pipe temperature gradient was within 15°C. The TEG's thermoelectric conversion efficiency of 7.5% and HPTEG's prototype system thermoelectric conversion efficiency of 6.2% were achieved. When the TEG hot surface temperature reached 625°C, the maximum electrical output power of the TEG peaked at 183.2 W, and the open‐circuit voltage reached 42.2 V. The high performances of the HPTEG prototype demonstrated the potential of the HPTEG for use in engineering applications. [ABSTRACT FROM AUTHOR]

In‐grain dislocation‐induced lattice strain fluctuations are recently revealed as an effective avenue for minimizing the lattice thermal conductivity. This effect could be integratable with electronic enhancements such as by band convergence, for a great advancement in thermoelectric performance. This motivates the current work to focus on the thermoelectric enhancements of p‐type PbTe alloys, where monotelluride‐alloying and Na‐doping are used for a simultaneous manipulation on both dislocation and band structures. As confirmed by synchrotron X‐ray diffractions and Raman measurements, the resultant dense in‐grain dislocations induce lattice strain fluctuations for broadening the phonon dispersion, leading to an exceptionally low lattice thermal conductivity of ≈0. 4 W m‐K−1. Band structure calculations reveal the convergence of valence bands due to monotelluride‐alloying. Eventually, the integration of both electronic and thermal improvements lead to a realization of an extraordinary figure of merit zT of ≈2.5 in Na0.03Eu0.03Cd0.03Pb0.91Te alloy at 850 K. [ABSTRACT FROM AUTHOR]

Entropy engineering is one of the powerful approaches to suppress phase transitions. GeTe has a very high thermoelectric performance at relatively high temperatures, but the low structure symmetry and phase transition in the low temperature range limits its performance stability for power generation applications. Therefore, the optimized electrical transport properties of GeTe in a low temperature range are expected for improving the structural symmetry via suppressing phase transition. Herein, the phase transition temperature for GeTe was successfully decreased by introducing high entropy via continuously multiple doping; the phase transition temperature is correspondingly reduced from 660 K to 523 K. The Seebeck coefficient was enhanced by the improved structural symmetry through enhancing band effective mass while the carrier concentration is maintained in an optimum range. A record-high power factor of ∼23 μW cm−1 K−2 was obtained at 300 K in the highest entropy sample. We found that the increased configurational entropy obtained by continuous, multiple doping produces short-range disordered microstructures, which lead to an ultralow lattice thermal conductivity of ∼0.4 W m−1 K−1. Combining the record high power factor and low thermal conductivity, a maximum ZT value of ∼2.1 at 800 K was achieved for the highest entropy species Ge0.84In0.01Pb0.1Sb0.05Te0.997I0.003. This study provides an effective path to enhance thermoelectric performances via introducing entropy engineering. [ABSTRACT FROM AUTHOR]

GeTe-based compounds have been intensively studied recently due to their superior thermoelectric performance, but their real applications are still limited so far due to the drastic volume variation that occurs during the rhombohedral–cubic phase transition, which may break the material or the material/electrode interface during service. Here, superior performance and high service stability for GeTe-based thermoelectric compounds are achieved by co-doping Mg and Sb into GeTe. The linear coefficient of thermal expansion before phase transition is greatly improved to match that after phase transition, yielding smooth volume variation around the phase transition temperature. Likewise, co-doping (Mg, Sb) in GeTe successfully tunes the carrier concentration to the optimal range and effectively suppresses the lattice thermal conductivity. A peak zT of 1.84 at 800 K and an average zT of 1.2 in 300–800 K have been achieved in Ge0.85Mg0.05Sb0.1Te. Finally, a Ni/Ti/Ge0.85Mg0.05Sb0.1Te thermoelectric uni-leg is fabricated and tested, showing quite good service stability even after 450 thermal cycles between 473 K and 800 K. This study will accelerate the application of GeTe-based compounds for power generation in the mid-temperature range. [ABSTRACT FROM AUTHOR]