Stability, electronic structures and thermoelectric properties of binary Zn–Sb materials

Abstract

We report first principles studies of the binary Zn–Sb phases in relation to thermoelectric properties and chemical stability. We identify the unknown structure of the Zn₃Sb₂ phase using particle swarm optimization, finding a tetragonal structure different from the hexagonal Mg₃Sb₂ and the hexagonal or cubic Ca₃Sb₂ phases. All the phases are found to be semiconducting with bandgaps in the range of 0.06–0.77 eV. This semiconducting behavior is understood in Zintl terms as a balance between the Zn : Sb and Sb³⁻ : ½(Sb₂)⁴⁻ ratios in the stable crystal structures. With the exception of Zn₃Sb₂, which has a small gap, all the compounds have electronic properties favorable for thermoelectric performance.