Simultaneously enhanced strength and plasticity of Ag2Se-based thermoelectric materials endowed by nano-twinned CuAgSe secondary phase

Thermoelectric materials strengthened by defect engineering can also suffer from the compromise of plasticity, and in turn results in negative effect on the processability, reliability and durability of thermoelectric devices. Here, we introduce nano-twinned CuAgSe secondary phase to achieve simultaneously increased compressive strength and plasticity of the β-Ag2Se pellets without obviously sacrificing the thermoelectric performance, as evidenced by our thermoelectric measurements. Our pellet shows a maximum compressive strength of 96 MPa, which is ∼104% higher than that of pristine Ag2Se, ascribed to the impeded crack propagation by the CuAgSe secondary phase. An extraordinary deformation value of ∼19% is observed at the maximum compressive strength, which is attributed to the intrinsically large plastic deformation of the Ag2Se matrix, the deformable nano-twinned CuAgSe secondary as well as the interaction between the Ag2Se matrix and the CuAgSe secondary phase. This work indicates that introducing nano-twinned secondary phase in thermoelectric materials is a promising strategy for developing high-performance thermoelectric materials with high strength and plasticity.