Computational Investigation of the Thermoelectric Performance of Environmentally Friendly and Earth-Abundant SrZn ₂ S ₂ O

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 p-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 n-type ZT value of 0.65 along the b direction and a maximum p-type ZT value of 0.77 along the c direction for SrZn2S2O.