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The segmented structure can effectively improve the performance of a thermoelectric generator (TEG), but the interfacial thermal stress between adjacent segments seriously threatens the reliability of segmented TEGs. Noticing this, we investigate the mechanical performance of a segmented TEG via theoretical and numerical methods. Results show that the structural stress depends on the ratio of cross-sectional areas between p- and n-type TE legs rather than the absolute cross-sectional areas, while the height ratio of different segments has a significant influence on structural stress. Different from structural stress, the thermal stress induced by unmatched thermal expansion between different segments increases rapidly with the increase of cross-sectional area, and can easily exceed 20% of the total interfacial stress. Besides, both the conversion efficiency and interfacial stress can be optimized by adjusting the ratio of cross-sectional areas. Our results provide the theoretical basis and guidance in the design of segmented TEGs. [ABSTRACT FROM AUTHOR]

A Bi 2 Te 3 -based thermoelectric generator (TEG) system cooled by heat radiation fin (HRF) applies to most scenarios of low-temperature power generation and waste heat recovery, while the high performance of the TEG system requires the precise design of the structure. Here we developed a theoretical model to simulate the thermal-electric coupling of the TEG system and analyzed the Bi 2 Te 3 -based TEG system with the aid of numerical and experimental methods. Results show that the increase in height of TEG not only improves the conversion efficiency but leads to a peak value of output power, which is much different from the traditional view that the output power solely decreases with the increase of height of TEG. Compared to the thickness of the fin, the height of the fin plays an essential role in optimizing the performance of TEG. By adding an electrical fan to improve the heat exchange coefficient, the net output power is doubled and the net conversion efficiency is improved by more than 80%. Besides, the structure of the TEG system is designed for different material parameters via the theoretical method. We anticipate that our results will guide the design and optimization of the TEG system. • Theoretical model simulates thermal-electric fields of TEG system. • Adjusting height of TEG leads to a peak value of output power. • Height of fin plays major role in optimizing performance of TEG system. • Additional fan doubles net output power and greatly improves efficiency. • Bi 2 Te 3 is proven by theoretical results to be a better choice for TEG system. [ABSTRACT FROM AUTHOR]

• In-situ performance of a thermoelectric generator in the core of a nuclear reactor. • Thermoelectric performance degrades under irradiation at low temperatures. • Significant recovery in performance under irradiation at high temperatures. • Operation at high temperature prevents unfavorable phase change. • Nanostructured thermoelectrics can provide stable power in the nuclear reactor core. Thermoelectric energy converters offer a promising solution to generate electrical power using heat in the nuclear reactor core. Despite significant improvements in thermoelectric efficiency of nanostructured materials, the performance of these advanced materials has yet to be demonstrated in the harsh radiation environment of a reactor core. Herein, we demonstrate a thermoelectric generator (TEG) made from nanostructured bulk half-Heusler (HH) materials generating stable electrical power density > 1140 W/m2 after 30 days in the MIT Nuclear Research Reactor under an unprecedented fast-neutron (>1 MeV) fluence of 1.5 × 1020 n/cm2. Despite an initial degradation due to irradiation damage when operating under relatively low temperatures, our TEG showed a 20-fold increase in power output when operating under high temperature due to in-situ annealing and resulting thermoelectric property recovery. First-principles modeling indicates that a chemically disordered metallic phase was formed under irradiation at lower temperatures, resulting in a drastic degradation in thermoelectric properties, while at sufficiently high temperatures the system returned to the initial chemically ordered HH phase and the thermoelectric properties recovered. Transmission electron microscopy and electron diffraction demonstrated that the chemically disordered phase was formed upon ion irradiation, confirming the prediction from first-principles simulations. The results suggest that with proper control over the TEG operating temperatures, the nanostructured bulk TEGs could produce stable electrical power and operate indefinitely in the core of a nuclear reactor. [ABSTRACT FROM AUTHOR]