Enhanced thermoelectric performance of AgBi3S5 by antimony doping

AgBi 3 S 5 is a promising n-type thermoelectric material with low lattice thermal conductivity. In this paper, polycrystalline bulk samples of n-type Ag 1− x Sb x Bi 3 S 5 ( x  = 0–0.03) were prepared by high-temperature reaction and pressed by spark plasma sintering (SPS). Electrical conductivity of AgBi 3 S 5 is enhanced significantly due to the increased carrier concentration. There is a remarkable enhancement of power factor from ~ 2.1 μW·cm −1 ·K −2 for undoped AgBi 3 S 5 to ~ 3.3 μW·cm −1 ·K −2 for Ag 0.97 Sb 0.03 Bi 3 S 5 . The Sb lone pair electrons, as indicated from density functional theory (DFT) calculation results, contribute to the Fermi energy and enhance the carrier effective mass. In addition, the point defects enhance phonon scattering and decrease the lattice thermal conductivity. Owing to the enhanced power factor and reduced thermal conductivity, the thermoelectric figure of merit ( ZT ) at 800 K for Ag 0.97 Sb 0.03 Bi 3 S 5 reaches 0.53, which is 70% higher than that of the pristine AgBi 3 S 5 .