High Thermoelectric Performance of AgSb1-xPbxSe2 Prepared by Fast Nonequilibrium Synthesis.

Abstract

AgSbSe2 is a typical member of cubic I-V-VI2 semiconductors, which are known for their extremely low lattice thermal conductivity (κl). 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 md* 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 κl, yielding a high ZT value of 1.2 at 723 K in AgSb0.94Pb0.06Se2. 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.