Semi-coherent interfaces synergistically optimize thermoelectric performance in Pb-doped Bi_0.4Sb_1.6Te₃

Nanoprecipitate engineering is an effective strategy to enhance the thermoelectric performance of Bi_2-xSb_xTe₃-based materials by increasing phonon scattering and decreasing lattice thermal conductivity. However, dense incoherent interfaces also intensify carrier scattering that limits overall performance improvement. In this study, we demonstrate that Pb doping induces semi-coherent interfaces to significantly enhance the thermoelectric performance of Bi_0.4Sb_1.6Te₃ through synergistic transport optimization. Pb doping lowers the formation energy of Sb vacancies, thereby promoting the formation of Sb nanoprecipitates with semi-coherent interfaces. These interfaces suppress carrier scattering, resulting in a high weighted mobility of 544 cm² V^-1 s^-1 and a power factor of 48 μW cm^-1 K^-2 at room temperature. Meanwhile, Sb nanoprecipitates effectively scatter phonons, leading to a low lattice thermal conductivity of 0.51 W m^-1 K^-1 at 460 K. Owing to these combined effects, the maximum figure-of-merit (ZT) increases from 0.81 for pristine Bi_0.4Sb_1.6Te₃ to 1.06 for Bi_0.4Sb_1.594Pb_0.006Te₃ at 460 K, with a peak conversion efficiency of ∼5.5% at a temperature difference of 200 K. This work demonstrates that introducing semi-coherent interfaces is an effective method to enhance the performance of Bi_2-xSb_xTe₃-based materials.