The utilization of thermoelectric devices that directly convert waste heat to electricity is an effective approach to alleviate the global energy crisis. However, the low efficiency of thermoelectric materials has puzzled the widespread applications. The CoSb3-based skutterudites are favored by device integration due to the excellent thermal stability, while the development of pristine CoSb3 materials is limited by the ultra-high thermal conductivity and the poor Seebeck coefficient. In this work, we demonstrate that both structural improvement and strong phonon interaction are realized simultaneously in In-filled CoSb3 coordinated with excessive Sb. The extra Sb compensates the deficiency on the Sb4 ring, improving the Seebeck coefficient, and cooperates with In to further advance the carrier concentration. Therefore, the structure optimization and chemical potential regulation maximize the electrical properties. Thermally, the residual InSb nanoparticles and partial In/Sb-alloying, along with vibration of In in voids, jointly shorten the multi-frequency phonon relaxation time, leading to a dramatic decline in the lattice thermal conductivity. As a result, a maximum zTmax of ∼1.27 at 650 K and an average zTavg of ∼0.9 from 300 to 750 K was obtained in In1.4Co4Sb12 + 8%Sb, respectively. Our findings provide valuable guidance for the selection of CoSb3-based skutterudite dopants to achieve high-performance thermoelectric materials.
Keywords: excessive indium; filled skutterudite; nanophase; phonon scattering; thermoelectric materials.