Atomic mechanism of ionic confinement in the thermoelectric Cu2Se based on a low-cost electric-current method

Abstract

Summary In a fast ion-conductor Cu2Se, phase instability and the loss of Cu under operational conditions are the major impediments to its thermoelectric applications. Herein, a fast and low-cost pulse electric current method is developed to rapidly synthesize Cu2Se-based materials with high thermoelectric performance. The Cu2Se microstructures under an external current and high temperature close to the real working conditions have been investigated by both ex situ and in situ transmission electron microscopy. Due to the presence of Bi interstitials, dynamic Cu-ion fluctuation zones on the nanometer scale have been stabilized through the pinning effect of dislocations and the action of interfacial/boundary phases steric hindrance, both preventing Cu ions from escaping from the lattice. The hierarchical structure spanning from interstitial atoms to nanometer-scale precipitates, created by the pulse electric current method, forms a network of ion-blocking but electrically conducting barriers that greatly improve the stability of Cu2Se-based thermoelectric materials.