Improving thermoelectric properties of Bi₂Te₃ by straining under high pressure: Experiment and DFT calculation

Bi₂Te₃ intermetallic compounds show high thermoelectric performance near room temperature and are widely used for cooling and power generation applications. It is still necessary to improve its dimensionless figure of merit zT for large-scale industrial use. In this study, high-pressure torsion processing is applied to Bi₂Te₃ powder samples to investigate the crystal structure and enhance their thermoelectric properties. The processed Bi₂Te₃ samples show reduced cell volume, higher electrical conductivity, enhanced Seebeck coefficient and higher zT value compared with the original powder sample, even if the grain refinement is not remarkable. First-principles calculations are also used to investigate the electronic structure and thermoelectric properties to clarify the influence of high-pressure torsion processing.