Direct hot deformation of as-grown n-type Bi2Te3 ingots: a simple thermoelectric optimization strategy

Abstract

As the only commercially applied thermoelectric material at room temperature, n-type Bi₂Te₃ suffers from a relatively low dimensionless figure of merit (zT), which limits the improvement of device conversion efficiency. The primary challenge in improving n-type Bi₂Te₃ performance lies in how to reduce the lattice thermal conductivity while maintaining the large-size grains and their orientation. Based on zone-melted ingots, we present a preparation method of hot deformation (ZM-HD) to resolve this issue. Benefiting from the donor-like effect, the ZM-HD samples exhibit an enhanced power factor of 59 μW cm⁻¹ K⁻² compared to the ZM counterparts. Combined with the decrease in lattice thermal conductivity caused by dense dislocations, the maximum zT of the ZM-HD samples reached 1.18 at 350 K. The obtained results are comparable to those of a previous report using the layered crystal stacking hot deformation method, saving the process of mechanical exfoliation. The maximum conversion efficiency of the prepared 17-pair thermoelectric module reached 6.2%. This work demonstrates a simple and efficient approach for the scalable fabrication of high-performance n-type Bi₂Te₃-based materials.