High Thermoelectric Performance of AgSb_1-PbSe₂ Prepared by Fast Nonequilibrium Synthesis

AgSbSe₂ is a typical member of cubic I-V-VI₂ semiconductors, which are known for their extremely low lattice thermal conductivity (κ_l). However, the low electrical conductivity of AgSbSe₂, below ∼10 S cm^-1 at room temperature, has hindered its thermoelectric performance. In this work, single-phase AgSbSe₂ bulk samples with much higher electrical conductivity were synthesized via self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) for the first time. Pb doping through the nonequilibrium process further increases the electrical conductivity to >100 S cm^-1. Furthermore, continuously increased effective mass m_d^* can be achieved upon Pb doping because of the multiple degenerate valence bands of AgSbSe₂ and the energy-filtering effect induced by in situ-formed nanodots. The simultaneous enhancement of both the electrical conductivity and Seebeck coefficient contributes to an unprecedentedly high average power factor of 6.75 μW cm^-1 K^-2. Meanwhile, the introduced dense grain boundaries and point defects enhance the phonon scattering and consequently suppress κ_l, yielding a high ZT value of 1.2 at 723 K in AgSb_0.94Pb_0.06Se₂. This study opens a new avenue for rapid, low-cost, large-scale production of AgSbSe₂-based materials and demonstrates that Pb-doped AgSbSe₂ prepared via the SHS-SPS method is a promising candidate for thermoelectric applications.