Simultaneous Enhancement of Strength and Ductility of Cu2-xSe through Dual-Phase Heterostructure

Abstract

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-xSe TE materials. We used solid-state sintering to obtain a coexisted Cu_2-xSe 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-3m, 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.