Enhanced High-Temperature\nThermoelectric Performance\nin Te-Doped Electronegative Element-Filled Skutterudites via Suppressing\nBipolar Effects and Enhanced Phonon Scattering

CoSb<sub>3</sub>-based skutterudites have great potential\nas midtemperature\nthermoelectric (TE) materials due to their low cost and excellent\nelectrical and mechanical properties. Their application, however,\nis limited by the high thermal conductivity and the degradation of\nTE performance at elevated temperatures, attributed to the adverse\neffects of bipolar diffusion. Herein, a series of Se<sub><i>y</i></sub>Co<sub>4</sub>Sb<sub>12–<i>x</i></sub>Te<sub><i>x</i></sub> compounds were successfully synthesized\nby combining a solid-state reaction and spark plasma sintering techniques\nto mitigate these challenges. It was found that doping Te at the Sb\nsites effectively enhanced the carrier concentration and suppressed\nthe bipolar effect to obtain a superior power factor of ∼43\nμW cm<sup>–1</sup> K<sup>–2</sup>. Furthermore,\ndue to the low resonant frequency of Se, filling voids of CoSb<sub>3</sub> with Se achieved a low lattice thermal conductivity of 1.55\nW m<sup>–1</sup> K<sup>–1</sup>. Nevertheless, Se filling\nintroduced additional holes, reducing the carrier concentration without\na significant detriment of the carrier mobility. As a result, a maximum\nfigure of merit of 1.23 was achieved for Se<sub>0.1</sub>Co<sub>4</sub>Sb<sub>11.55</sub>Te<sub>0.45</sub> at 773 K. This work provides\na valuable guidance for selecting appropriate filling and doping components\nto achieve synergistic optimization of the acoustics and electronics\nof CoSb<sub>3</sub>-based skutterudites.