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Filled Skutterudites are one group of the most promising thermoelectric materials in real power generation applications. Herein, homogeneously dispersed multiscale CoSi nanostructures are successfully embedded into grains of the classic skutterudite system, Yb0.3Co4Sb12, by the in situ precipitation method. Such nanoprecipitates contribute much to the synergistic enhancement of thermoelectric and mechanical properties. On one hand, by the fine deployment of multiscale CoSi nanoparticles, the lattice thermal conductivity is significantly depressed almost to the theoretical limit because of the disrupted propagation of the heat‐carrying phonons at phase boundaries. On the other hand, low‐energy electrons are effectively screened due to the energy filtering effect by the interfacial potential barrier between the CoSi nanoprecipitate and the matrix, resulting in an enhanced power factor. Taken together, an enhanced peak ZT value of ≈1.5 at 873 K for the Yb0.3Co4Sb12/0.05CoSi composite is obtained with a high average ZT ≈0.95 between 300 and 873 K through decoupling the electrical and thermal transport parameters. Moreover, such a microstructure with multiscale CoSi nanoparticles shows significantly improved mechanical properties owing to particle hardening, making it more competitive for practical applications.

Bi-based Zintl phase CaMg2Bi2 is a promising thermoelectric material. Here, we report that the high-concentration point defects induced by equivalent Zn doping on the Mg site significantly enhance phonon scattering and then suppress lattice thermal conductivity by 50% at room temperature. Subsequently, partial substitution of divalent calcium ions with alkali-ion doping (Li, Na, K) not only optimizes the electrical transport properties by increasing the carrier concentration but also further reduces the lattice thermal conductivity through crystal disorder. Finally, the synergistic effect of Zn and Li co-doping leads to a high ZT of ∼1.0 at 873 K and an average ZT of 0.6 between 300 and 873 K for Ca0.995Li0.005Mg1.9Zn0.1Bi1.98. This work demonstrates an instructive method to reduce the lattice thermal conductivity via doping at the Mg site, which has never been reported in the CaMg2Bi2 system. Moreover, high-performance Ca0.995Li0.005Mg1.9Zn0.1Bi1.98 alloy does not contain any toxic elements and expensive rare earth elements, which is of great significance for the development of environment-friendly thermoelectric materials.

Herein, we demonstrate a synergistic combination of novel mechanisms in aluminum (Al)-alloyed Yb 0.3 Co 4 Sb 12 -based thermoelectric materials to address both reduction in thermal conductivity and concomitant enhancement in power factor (PF). Upon Al alloying, CoAl nanoprecipitates are embedded in the matrix, leading to (1) significant local strain and thus intensified phonon scattering and (2) carrier injection because of interphase electron transfer. Moreover, by decreasing the Yb filling fraction, not only is the electronic thermal conductivity significantly suppressed but also the carrier concentration is modulated to the optimum range, thus resulting in the dramatically boosted PF, especially below 773 K. As a result, a peak ZT value of 1.36 at 873 K and ZT ave of 0.96 from 300 to 873 K were obtained in Yb 0.21 Co 4 Sb 12 /0.32CoAl. Last but not the least, the mechanical properties of the Al-alloyed samples were considerably improved through CoAl precipitate hardening, offering great potential for commercial applications.