Efficient Si Doping Promoting Thermoelectric Performance of Yb-Filled CoSb₃-Based Skutterudites

Nanocomposites have become a widely popular way to assist in the enhancement of thermoelectric performance for filled skutterudites. Herein, we unveil the distinctive effect of Si doping on the classic Yb_0.3Co₄Sb₁₂. On the one hand, the reduced Yb filling fraction is accompanied by the in-situ precipitated CoSi nanoparticles, which not only enhances the power factor in the intermediate-low temperature range but also reduces electronic thermal conductivity for decreasing the carrier concentration. On the other hand, CoSi nanoparticles intensively disrupt the phonon transport, hiding the increased lattice thermal conductivity due to reduced Yb filling fraction. Although the residual YbSb₂ second phases have an adverse effect on the thermoelectric properties, the integration effects achieve a peak ZT value of 1.37 at 823 K and increase ZT_ave by 21% for the Yb_0.3Co₄Sb₁₂/0.1Si sample.