Thermoelectric Enhancement in BaGa2Sb2 by Zn Doping

The Zintl phase BaGa2Sb2 has a unique crystal structure in which large tunnels formed by ethane-like dimeric [Sb3GaGaSb3] units are filled with Ba atoms. BaGa2Sb2 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 similar to 0.4 eV. The thermal conductivity of BaGa2Sb2 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 BaGa2Sb2 has a low carrier concentration (similar to 2 x 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 (58) x 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 similar to 0.6 at 800 K. Zn-doped BaGa2Sb2 can thus be considered as a promising new thermoelectric material for intermediate-temperature applications.