Thermoelectric Cooling Performance Enhancement in BiSeTe Alloy by Microstructure Modulation via Hot Extrusion

The demand for high-performance materials in thermoelectric (TE) technology has driven continuous efforts to enhance the performance of commercialized Bi2Te3-based thermoelectric materials. Here, we report success in achieving significant performance improvements in n-type Bi2Te2.8Se0.2S0.01 through the implementation of a hot extrusion manufacturing process. This tailored manufacturing process has yielded a desired microstructure characterized by grain growth and preferred orientations. The resulting enlarged grain-based microstructure exhibits reduced dislocations and defects that originated from plastic deformation during extrusion and post annealing. As such, the charge carrier mobility is significantly enhanced, leading to an ultrahigh power factor of approximately 51 mu W cm-1 K-2 at ambient temperature. Consequently, a maximum figure of merit (zT) of 1.12 is achieved at 348 K in the combination of extrusion and annealing procedures. Using the synthesized n-type Bi2Te2.8Se0.2S0.01 material, full-scale cooling modules have been fabricated. These modules demonstrate record cooling performance, with a maximum temperature difference (Delta T) of 73.9 K at a hot-side temperature of 300 K and a maximum cooling power density of 2.2 W cm-2. The cooling performance of these TE devices surpasses that of commercially available devices, establishing their potential for next-generation TE cooling applications. The breakthrough in enhancing n-type Bi2Te2.8Se0.2S0.01's performance involves a specialized hot extrusion method, resulting in an optimal microstructure marked by grain growth and preferred orientations. This tailored manufacturing approach, combined with annealing, attains a remarkable zT of 1.12. The cooling modules exhibit unprecedented cooling performance, showcasing a record temperature difference of 73.9 K.image (c) 2023 WILEY-VCH GmbH