Simultaneous enhancement of strength and ductility of Cu2-Se through dual-phase heterostructure

High-performance thermoelectric (TE) materials usually exhibit brittleness and poor ductility, which limits their device fabrication and applications in flexible and deformable electronics. In this work, we propose a dual-phase heterostructure strategy to simultaneously improve the strength and ductility of Cu _{2- x}Se TE materials. We used solid-state sintering to obtain a coexisted Cu _{2- x}Se structure with a hard α-phase (space group of C2/c, poor ductility, and high yield strength) and a soft β-phase (space group of Fm-3 m , superior ductility, and lower yield strength). Owing to the large strain hardening of the β-phase and the back stress strengthening effect of the heterostructure, the fracture strain, yield strength, and compressive strength of the heterostructured Cu _1.88Se material were simultaneously improved by 266 %, 16 %, and 44 %, respectively, compared to the homogeneous Cu _1.93Se material. This study proposes an effective dual-phase heterostructure strategy for synergistically enhancing the strength and ductility of intrinsically brittle TE semiconductor materials.