Thermoelectric Enhancement in BaGa₂Sb₂ by Zn Doping

The Zintl phase BaGa 2 Sb 2 has a unique crystal structure in which large tunnels formed by ethane-like dimeric [Sb 3 Ga–GaSb 3 ] units are filled with Ba atoms. BaGa 2 Sb 2 was obtained in high purity from ball-milling followed by hot pressing. It shows semiconducting behavior, in agreement with the valence precise Zintl counting and band structure calculations, with a band gap ∼0.4 eV. The thermal conductivity of BaGa 2 Sb 2 is found to be relatively low (0.95 W/K m at 550 K), which is an inherent property of compounds with complex crystal structures. As BaGa 2 Sb 2 has a low carrier concentration (∼2 × 10 18 h + /cm 3 ) at room temperature, the charge carrier tuning was performed by substituting trivalent Ga with divalent Zn. Zn-doped samples display heavily doped p-type semiconducting behavior with carrier concentrations in the range (5–8) × 10 19 h + /cm 3 . Correspondingly, the zT values were increased by a factor of 6 by doping compared to the undoped sample, reaching a value of ∼0.6 at 800 K. Zn-doped BaGa 2 Sb 2 can thus be considered as a promising new thermoelectric material for intermediate-temperature applications.