Enhanced thermoelectric performance of AgBi3S5 by antimony doping

AgBi3S5 is a promising n-type thermoelectric material with low lattice thermal conductivity. In this paper, polycrystalline bulk samples of n-type Ag1−xSbxBi3S5 (x = 0–0.03) were prepared by high-temperature reaction and pressed by spark plasma sintering (SPS). Electrical conductivity of AgBi3S5 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 AgBi3S5 to ~ 3.3 μW·cm−1·K−2 for Ag0.97Sb0.03Bi3S5. 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 Ag0.97Sb0.03Bi3S5 reaches 0.53, which is 70% higher than that of the pristine AgBi3S5.