Enhanced Thermoelectric and Mechanical Performance in n-Type Yb-Filled Skutterudites through Aluminum Alloying.

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.