The effects of alkaline-earth-metal-element doping on the thermoelectric properties of β-Zn4Sb3☆

The effects of alkaline-earth metal elements Ca, Sr, and Ba on the electronic structure and thermoelectric properties of beta-Zn4Sb3 were investigated by performing self-consistent ab initio electronic structure calculations within density functional theory and solving the Boltzmann transport equations within the relaxation time approximation. The results demonstrate that these alkaline-earth metal elements with s orbitals could introduce giant sharp resonant peaks in the electronic density of states (DOS) near the host valence band maximum in energy. And these deliberately engineered DOS peaks result in a sharp increase of the room-temperature Seebeck coefficient of beta-Zn4Sb3 by a factor of nearly 8/9/19, respectively. Additionally, with the simultaneous increase of conductivity and decline of carrier thermal conductivity upon Ca/Sr/Ba doping, potentially, at least, 10/4/2-fold increase in optimizing power factor, and 14/12/8-fold increase in thermoelectric figure of merit of beta-Zn4Sb3 at room temperature are achieved. And their corresponding optimal Fermi levels are all located near the host valence band maximum.