BaGa2Sb2 was obtained from a direct element combination reaction in a sealed graphite tube at 950.degree., and its structure was detd. by single-crystal x-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma with a 25.454(5), b 4.4421(9), c 10.273(6) .ANG., and Z = 8. The anionic [Ga2Sb6/3]2- framework is assembled by the ethane-like dimeric [Sb3Ga-GaSb3] units sharing Sb atoms, forming parallel tunnels with a 26-membered ring cross section. These tunnels are filled with Ba atoms. The three-dimensional [Ga2Sb6/3]2- framework features a new structure type. The compd. satisfies the classical Zintl concept. Band structure calcns. indicate that the material is a semiconductor, and this is confirmed by spectroscopic expts. which show Eg .apprx. 0.35 eV. The calcns. also suggest that the structure is stabilized by strong Ga-Ga covalent bonding interactions. Polycryst. ingots of BaGa2Sb2 show room-temp. elec. cond. of .apprx.65 S/cm and a Seebeck coeff. of +65 .mu.V/K.
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