Direct Hot Deformation of As-Grown n-Type Bi2Te3 Ingots: A Simple Strategy to Thermoelectric Optimization

Abstract

As the only commercially applied thermoelectric material, n-type Bi2Te3 suffers the relatively low dimensionless figure of merit (zT), which constrains 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 preparing 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 by dense dislocations, the maximum zT of ZM-HD samples reaches 1.18 at 350 K. The obtained results are comparable to the previous report using the layered crystal stacking hot deformation (LCSHD) method, but saving the process of mechanical exfoliation. The maximum conversion efficiency of the prepared 17-pair thermoelectric module reached 6.2%. This work has demonstrated a simple and efficient approach for the scalable fabrication of high-performance n-type Bi2Te3-based materials.