Stepwise Optimization of Thermoelectric Performance in <scp> Cu ₃ SbSe ₄ </scp> ‐Based Compounds via Alloying and Hierarchical Structuring

Cu 3 SbSe 4 ‐based compounds have attracted considerable potential in the realm of thermoelectric research owing to their distinctive physical properties and environmental compatibility. The material was efficiently synthesized via rapid microwave melting processing, aiming to improve its viability as a cost‐effective thermoelectric option for practical applications. This study emphasizes the stepwise optimization of thermoelectric transport properties. The foremost effort involved improving transport electrical transport properties through the co‐alloying of Sn and Te to determine optimal compositional configurations for superior thermoelectric performance. Iterative refinement enabled increased hole carrier concentration, which effectively addressed the intrinsic limitation of low electrical conductivity, thereby increasing the power factor by three times. Based on this foundation, a hierarchical multiscale structure was developed through the incorporation of AgCuTe as a secondary phase, which enhanced phonon scattering across multiple scales and consequently reduced thermal conductivity by 65% relative to pristine samples. The synergistic optimization of electronic and thermal transport properties culminated in a significant improvement in zT . The optimized Cu 3 SbSe 4 –1.0 wt% (Sn, Te)‐2.5 wt% AgCuTe composite demonstrated a peak zT of 1.21 at 650 K and an average zT avg of 0.52 across the range of 300–650 K, contributing to a deeper understanding of the transport properties for chalcogenide‐based thermoelectric compounds.