Abstract
The title compounds were synthesized from the elements by heating the corresponding stoichiometric mixtures at high temperature. Their structures were determined from single-crystal X-ray diffraction. Na~2~Ba~4~Ga~2~Sb~6~ (Pnma, Z = 8, a = 12.3468(10) Γ
, b = 10.6621(10) Γ
, c = 13.8344(10) Γ
) contains chains of ~β~[Ga~2~Sb~6~]^10β^. The repeating unit is made of an edge-sharing Ga-centered tetrahedron GaSb~2~(ΞΌ-Sb)~2~ and another Ga-centered tetrahedron but with additional antimony that is exo-bonded to one of the corners forming SbβSb dumbells, i.e. GaSb(SbβSb)(ΞΌ-Sb)~2~. The unit connects to neighboring units via sharing two corners of the tetrahedra, i.e. [Ga~2~Sb~5~Sb~2/2~]. Li~13~Ba~8~GaSb~12~ (__C__2/m, Z = 2, a = 18.0650(10) Γ
, b = 4.9407(10) Γ
, c = 13.0123(10) Γ
, Ξ² = 126.728(10)Β°) contains three different types of anions: single-atom anions of Sb^3β^, dumbells of Sb^4β^, and isolated Ga-centered tetrahedra of GaSb~4~
^9β^. The two compounds are electronically balanced, and this is confirmed by four-probe conductivity and magnetic measurements. Their very narrow band gaps, 0.014 and 0.049 eV for Na~2~Ba~4~Ga~2~Sb~6~ and Li~13~Ba~8~GaSb~12~, respectively, make them potential thermoelectric materials.