Optimizing Thermal-Mechanical Processes for High In-Plane Texture and Thermoelectric Performance of n-type Bi2Te3

Abstract

The layered Bi2Te3 is currently the only commercialized thermoelectric material whose performance is highly contingent on the in-plane crystallographic texture, particularly for the n-type Bi2Te3. In recent years, the demand for robust mechanical strength in practical applications has driven advancements in hot extrusion techniques for material fabrication but with considerable room for texture optimization. Herein, the primary slip systems activated during the plastic deformation of Bi2Te3 were firstly identified, and a Taylor model to simulate the texture evolution of the hot-extruded samples under various conditions was developed. Subsequently, by simply aligning the extrusion direction with the initial in-plane texture, we achieved at least a doubling of the texture degree, resulting in the extremely high room temperature carrier mobility 263 cm2V-1s-1 and power factor ~47.3 μWcm-1K-2, which contributes to the high dimensionless figure of merit ~1.05@ 375K. Under the guidance of the same method, another hierarchical Bi2Te2.7Se0.3 with a high 1.08@ 450 K was also achieved, based on which a segmented thermoelectric generator module was fabricated and realized a high conversion efficiency of 7.6% at a temperature difference of 293 K. Therefore, these results underscore that the fabrication of target microstructures based on an understanding of microstructure evolution and prediction will significantly propel the development of thermoelectric materials.

Keywords: Bi2Te3, hot extrusion, Microstructure evolution, Taylor model, Segmented module