Enhancing Thermoelectric Performance in P-Type Sb₂Te₃-Based Compounds Through Nb─Ag Co-Doping with Donor-Like Effect

P-type Sb₂Te₃ has been recognized as a potential thermoelectric material for applications in low-medium temperature ranges. However, its inherent high carrier concentration and lattice thermal conductivity led to a relatively low ZT value, particularly around room temperature. This study addresses these limitations by leveraging high-energy ball milling and rapid hot-pressing techniques to substantially enhance the Seebeck coefficient and power factor of Sb₂Te₃, yielding a remarkable ZT value of 0.55 at 323 K due to the donor-like effect. Furthermore, the incorporation of Nb─Ag co-doping increases hole concentration, effectively suppressing intrinsic excitations ≈548 K while maintaining the favorable power factor. Simultaneously, the lattice thermal conductivity can be significantly reduced upon doping. As a result, the ZT values of Sb₂Te₃-based materials attain an impressive range of 0.5-0.6 at 323 K, representing an almost 100% improvement compared to previous research endeavors. Finally, the ZT value of Sb_1.97Nb_0.03Ag_0.005Te₃ escalates to 0.92 at 548 K with a record average ZT value (ZT_avg) of 0.75 within the temperature range of 323-573 K. These achievements hold promising implications for advancing the viability of V-VI commercialized materials for low-medium temperature application.