Abstract: AgSbTe₂-based materials have recently garnered significant attention due to their exceptional thermoelectric properties; however, their inherent cation disorder and secondary phase result in poor electrical conductivity. In this study, we demonstrate that introducing Ag vacancies and Sb₂Te₃ into AgSbTe₂ induces synergistic effects: i) enhanced phonon scattering, contributing to an ultralow lattice thermal conductivity of ∼0.19 W m^-1 K^-1 at 514 K; ii) reduced carrier scattering, leading to a high carrier mobility of ∼692.20 cm² V^-1 s^-1 at 513 K and a high power factor of ∼18.2 µW cm^-1 K^-2 at 514 K; iii) improved solubility of the Ag₂Te secondary phase, resulting in enhanced of phase stability AgSbTe₂. As a result, the (Ag_0.97SbTe₂)_0.994(Sb₂Te₃)_0.006 sample achieves a peak figure-of-merit of ∼2.1 at 514 K and an impressive average figure-of-merit of ∼1.47 over the temperature range of 300-514 K. This work provides a progressive design strategy for high-performance low-temperature thermoelectric power generation materials.

Key words: Carrier mobility, Lattice thermal conductivity, Figure-of-merits, Sb₂Te₃, AgSbTe₂