Low Thermal Conductivity and Optimized Thermoelectric Properties of p-Type Te-Sb2Se3: Synergistic Effect of Doping and Defect Engineering.

Abstract

Elemental tellurium exhibits a promising thermoelectric performance, largely due to the optimization of the carrier concentration stemming from effective chemical doping. In this study, we demonstrate a novel approach to realize the collaborative manipulation of the electrical and thermal transport properties in the Te system via introduction of Sb2Se3. A series of p-type Te1-x(Sb2Se3)x (0 ≤ x ≤ 0.2) samples were fabricated through the melting method followed by spark plasma sintering. Electrically, antimony as a successful dopant enables a remarkable improvement of the carrier concentration, from ∼1018 to ∼1019 cm-3, thus resulting in a desired power factor across the entire temperature range. Thermally, utilization of defects engineering containing point defects, grain boundaries, dislocations, and secondary phase precipitates effectively reduces the lattice thermal conductivity. The coexistence of multi-frequency phonon scattering centers derived from the addition of Sb2Se3 leads to a minimum lattice thermal conductivity of 0.5 W m-1 K-1, approaching the amorphous limit. As a result, Te0.95(Sb2Se3)0.05 shows the highest figure of merit ZT ∼1 at 600 K, comparable to that of the toxic Te(As) thermoelectrics. This work not only points out that synergistic effects of both doping and defect engineering play a vital role in decoupling the thermoelectric parameters in the Te1-x(Sb2Se3)x system but also gives a referential strategy for a higher thermoelectric performance in other Te-based materials.