Enhancement of the thermoelectric properties of BaCu2Se2 by potassium doping

Layered compounds play an important role in thermoelectric materials exploration, as their thermal and electrical conductivities could be affected by different layers. Herein, we have synthesized a new layered Ba0.7K0.3Cu2Se2 phase with the ThCr2Si2 structure through 30% K doping on the Ba sites in the pristine orthorhombic BaCu2Se2. The layered Ba0.7K0.3Cu2Se2 exhibits intrinsically low lattice thermal conductivity due to its extremely short phonon mean free path. Ba0.7K0.3Cu2Se2 also features high hole mobility and reasonable Seebeck coefficient at high doping levels. The enhancement of electrical conductivity is mainly ascribed to the increase of the hole concentration and the unchanged high hole mobility. As a result, the peak ZT of Ba0.7K0.3Cu2Se2 reaches 0.32 at 800 K, which is of significance by comparing to its undoped BaCu2Se2 counterpart.