First-principles study of Zn-Sb thermoelectrics

We report local-density-approximation calculations of the electronic structure and thermoelectric properties of $\beta -{\mathrm{Zn}}_4{\mathrm{Sb}}_3$. The material is a low carrier density metal with a complex Fermi-surface topology and a nontrivial dependence of the Hall concentration on the band filling. The band structure is rather covalent, consistent with experimental observations of good carrier mobility. At a band filling corresponding to the experimental Hall number, the calculated thermopower and temperature dependence are in good agreement with experiment. The high Seebeck coefficient in a metallic material is remarkable, and arises in part from the strong energy dependence of the Fermi surface topology near the experimental band filling. An improved thermoelectric performance is predicted for lower doping levels, i.e., higher Zn concentrations.