Computational Investigation of the Thermoelectric Performance of Environmentally Friendly and Earth-Abundant SrZn<sub>2</sub>S<sub>2</sub>O.

Abstract

Thermoelectric (TE) materials enable direct conversion between heat and electricity, allowing efficient recovery of waste heat, which accounts for nearly 50% of global energy consumption. Therefore, TE materials hold great potential for applications in waste heat recovery and sustainable energy technologies. Owing to the composition of earth-abundant and low-toxicity elements, as well as the presence of relatively heavy elements and mixed-anion characteristics, SrZn₂S₂O is considered a promising, environmentally friendly TE material. In this study, the TE performance of SrZn₂S₂O was investigated based on density functional theory (DFT) and compared with that of the prototypical mixed-anion oxide BiCuSeO. The calculated results show that SrZn₂S₂O exhibits a higher optimal average <i>p</i>-type power factor than that of BiCuSeO at 900 K, reaching 1150 μW m^-1 K^-2 compared with 770 μW m^-1 K^-2 for BiCuSeO. In addition, nanostructuring strategies can reduce the lattice thermal conductivity of SrZn₂S₂O by 40% or more in all crystallographic directions. This leads to a maximum <i>n</i>-type <i>ZT</i> value of 0.65 along the <i>b</i> direction and a maximum <i>p</i>-type <i>ZT</i> value of 0.77 along the <i>c</i> direction for SrZn₂S₂O.