Low Thermal Conductivity Induced Thermoelectric Improvement in Pristine SnTe via High-Pressure Engineering

Lead chalcogenide-based compounds (SnTe) are state-of-the-art thermoelectric materials. However, the performance of environmentally friendly p-type SnTe is inferior due to its high hole concentration and high thermal conductivity. However, a high-pressure strategy is a beneficial method for property improvement through structural modification and defect engineering. Herein, we investigated the behaviors of different defects upon the different pressures and found that the formation energy of V-Sn(2-) is gradually increased with the increased pressure, which suggests that the high hole concentration can be reduced to some extent. Meanwhile, the thermoelectric performance of SnTe synthesized under high pressure (HP) is investigated and compared with that of samples prepared by conventional spark plasma sintering (SPS). Importantly, the thermal conductivity has a huge decrease from 4.27 to 1.67 Wm(-1) K-1 due to the stronger phonon scattering originating from formed nanoparticles under HP. As a result, a large ZT(max) similar to 0.40 (at 773 K) is achieved for the pure SnTe sample at 2 GPa pressure, which is similar to 40% larger than that SnTe sample obtained by SPS. Present results demonstrate that the high-pressure synthesis is an effective way to improve the thermoelectric performance of SnTe, suggesting that HP is an alternative measure for designing thermoelectric materials.