Boosting the thermoelectric performance of Bi2S3 by CeCl3 addition and hydrothermal synthesis

Bi₂S₃ is a potential thermoelectric material due to its high Seebeck coefficient (S), low thermal conductivity (κ) and environmentally friendly elemental composition. However, pristine Bi₂S₃ suffers from a low thermoelectric performance primarily owing to the intrinsic low electrical conductivity (σ). In this work, we employ CeCl₃ doping to promote the σ of Bi₂S₃ by a hydrothermal method. Doping 1.0 % mol CeCl₃ provides more electrons to increase the carrier concentration to 2.73 $\times$ 10¹⁹ cm⁻³ of Bi₂S₃ at room temperature, which leads to significant high σ and power factor of 242 μW m⁻¹ K⁻² at 573 K. In addition, the formation of micro–nano pores in the doped Bi₂S₃ bulk samples contribute to the phonon scattering as well as the reduction of lattice thermal conductivity. A peak ZT of ∼0.31 at 623 K is obtained in the Bi₂S₃ bulk sample doped with 1.0 % mol CeCl₃, which is almost twice as high as the pristine Bi₂S₃. Simultaneously, the Vickers hardness of 1.0 % mol CeCl₃ doped Bi₂S₃ samples achieves to approximately 1.28 GPa, which is enhanced by nearly 40 % compared to pristine Bi₂S₃. This study has provided a facile method for realizing high thermoelectric performance and high mechanical property of Bi₂S₃ materials.