Resolving the thermoelectric‐mechanical performance trade‐off in n ‐type Bi 2 Te 3 ‐based compounds via a novel melt‐spinning and hot‐extrusion route

Abstract Bi 2 Te 3 ‐based materials are the best commercial thermoelectric (TE) materials for applications near room temperature. However, zone‐melted (ZM) materials suffer from poor mechanical properties, while traditional powder metallurgy‐derived Bi 2 Te 3 exhibits a strong donor‐like effect when refined into fine grains, creating a fundamental barrier to the simultaneous enhancement of mechanical and TE performance. Herein, high‐performance n ‐type Bi 2 Te 3 ‐based materials were fabricated via a hybrid process combining melt spinning (MS) and hot extrusion (HE). The MS‐derived foils exhibit a strong (110) orientation, nanocrystalline structure, and no significant donor‐like effect despite air exposure. These characteristics of these foils are maintained in the precursor for HE via rapid sintering by directly laying the foils flat without grinding. This strongly oriented, fine‐grained characteristic of the ribbon precursor is inherited and further intensified via subsequent HE, which yields fine‐grained, highly textured bulk materials with an orientation factor F (110) of 0.54. The enhanced texture and microstructure result in a high carrier mobility of 348 cm 2 ·V −1 ·s −1 and a power factor of 52.20 µW·cm −1 ·K −2 , while intensifying phonon scattering and reducing lattice thermal conductivity to 0.5 W·m −1 ·K −1 . Consequently, a peak ZT of 1.25 at 345 K and a room temperature ZT of 1.12 are achieved. This material also demonstrates exceptional mechanical properties, with a record‐high compressive strength of 338 MPa and flexural strength of 153.8 MPa. This work resolves the longstanding trade‐off between mechanical robustness and TE efficiency, enabling the fabrication of TE legs (<100 µm) for large‐scale applications. It paves the way for the fabrication of micro‐TE devices.