High-Performance p-Type Bi₂Te₃-Based Thermoelectric Materials with a Wide Temperature Range Obtained by Direct Sb Doping

Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi₂Te₃-based alloys. P-type Bi_2−xSb_xTe₃ thermoelectric materials have been successfully prepared by direct Sb doping method. It can be found that doping Sb into Bi₂Te₃ lattice array for Bi-site replacement facilitates the generation of Sb′_Te anti-site defects. This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_2−xSb_xTe₃ alloys. In addition, the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity. As a result, the Bi_0.47Sb_1.63Te₃ sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K. It is worth noting that the bipolar effect of Bi₂Te₃-based alloys can be weakened with the increase of Sb content. The Bi_0.44Sb_1.66Te₃ sample has a maximum average ZT value (0.93) in the temperature range of 300–500 K, indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value. This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.