Effect of plastic hot-rolling on thermoelectric properties in Ag2Se0.65S0.35 ductile materials

Abstract

Ag₂(S, Se) solid solutions near the morphotropic phase boundary (MPB) well integrate excellent room-temperature ductility and high thermoelectric (TE) performance together, showing the great potential for the usage in flexible thermoelectrics. However, their orthorhombic-monoclinic phase transition brings great difficulty to fabricate the Ag₂(S, Se)-based flexible films with high TE performance. In this work, taking the Ag₂Se_0.65S_0.35 which locates at the orthorhombic-monoclinic phase boundary as an example, we systematically investigate the evolutions of phase and electrical transport properties of Ag_2-xSe_0.65S_0.35 during the plastic hot-rolling and the following post-treatment processes. Significantly degraded power factor is observed with increasing the deformation degree, but it can be recovered back by post-treatment, i.e. firstly annealing at 353 K and then dipping in liquid nitrogen. Finally, high-performance flexible Ag₂Se_0.65S_0.35 film with a room-temperature power factor of 17.0 μWcm^-1K^-2 is successfully obtained, providing a promising candidate materials for the development of flexible TE device used in wearables.