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|a Thermoelectric power generation represents a class of energy conversion technology, which has been used in power supply of aeronautic and astronautic exploring missions, now showing notable advantages to harvest the widely distributed waste heat and convert the abundant solar energy into electricity at lower cost than Si-based photovoltaic technology. Thermoelectric dimensionless figure of merit (ZT) plays a key role in the conversion efficiency from thermal to electrical energy. Most state-of-the-art thermoelectric materials are characterized with various nanostructures from fine grains, dispersed particles, nano-inclusions to atomic defects, and therefore are referenced as nanocomposite. Recently, remarkable advances have been achieved in various material systems through the introduction of different nanostructures to tune the transport of phonons and electrons. In this review, we firstly clarify some fundamental tradeoffs dictating the ZT value through the relationship ZT=(S²σ/κ)T. We also pay special attentions to the recent advances in some selected materials, including half-Heuslers, PbTe, CoSb₃, Bi₂Te₃, etc. Finally, we provide an outlook of new directions in this filed, especially a proposal on a new concept of ordered nanocomposite. Graphical abstract This paper reviews the recent advances in thermoelectric nanocomposite materials including half-Heuslers, skutterudites, PbTe, PbSe, PbS, AgSbTe₂, and Bi₂Te₃-based materials, with a special attention given to the fundamental tradeoffs dictating the ZT values. A large reduction in lattice thermal conductivity has been demonstrated in these materials due to the presence of nanostructures, leading to higher ZTs. To further improve the ZT, a new concept of ordered nanocompositeis proposed. Highlights ► Thermoelectric power generation represents a class of clean energy conversion technology. ► Some fundamental tradeoffs limit the ZT value through the relationship ZT=(S²σ/κ)T. ► The concept of nanocomposite increases the ZT value of the state-of-the-art materials. ► A new concept of ordered nanocomposite is proposed.
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