Improved thermoelectric properties of n-type Bi₂S₃ via grain boundaries and in-situ nanoprecipitates

To improve the thermoelectric properties of n-type Bi₂S₃ materials, a certain amount of SbCl₃ were added into Bi₂S₃ materials by a conventional melting method combined with plasma activated sintering (PAS) process. The Bi₂S₃-based materials evolve from the lamellar- to particle-like structures after SbCl₃ doping. The phonon scattering has strong enhancement through the increased grain boundaries and in-situ Bi₂S₃ nanoprecipitates, resulting in the low lattice thermal conductivity. Meanwhile, the high power factor is achieved because of the marked increase in the electrical conductivity. Hence, the synergistic effect of antimony and chlorine substitutions not only contribute to reduce the thermal conductivity but also tune the electrical transport properties, yielding a peak ZT value of ∼ 0.65 at 773 K for the Bi₂S₃-1%SbCl₃ sample.