Synthesis, crystal structure, and thermoelectric properties of vacancy-doped praseodymium sulfide

Thermoelectric materials emerge as a promising avenue for inter-quality energy transformation, specifically harnessing waste heat into electrical energy. Herein, we present a novel rare-earth-based thermoelectric compound, Pr₂S_3−x (x = 0.04, 0.06, and 0.08). The joint analysis of X-ray diffraction and X-ray absorption fine structure spectra (XAFS) is performed on the crystallographic structure and to decipher the coordination environment of the nearest neighboring Pr–S atomic pairs. Furthermore, multiple scattering ascertains the three main features of the Pr L₃-edge XAFS in Pr₂S₃. The electrical conductivity and Seebeck coefficient of Pr₂S_3−x could be adjusted by changing the anion vacancy. A reasonable peak power factor of 2.49 µW/cm/K² is achieved at 623 K for Pr₂S_3−x (x = 0.04). Band structure calculations reveal the Γ point of the Brillouin zone in the conduction band region, featuring a single dispersive band. Meanwhile, the valence band exhibits the convergence of multiple bands, implying that it has greater potential in p-type TE semiconductors. Additionally, the mechanical properties of Pr₂S_3−x were investigated by the hardness testing and sound velocity measurement. This comprehensive study on the Pr₂S_3−x material system represents a significant step forward in expediting the development of innovative thermoelectric materials.