Synthesis, Structure and Charge Transport Properties of Yb(5)A(12)Sb(6): A Zintl Phase with Incomplete Electron Transfer

We report the synthesis, structure, spectroscopic properties, charge and thermal transport, and electronic structure of a new member of the Zintl family, Yb(5)A(12)Sb(6). The compound crystallizes in the Ba5Al2Bi6 structure type and requires the addition of Ge or Si in the synthesis, which years to act as a catalyst. Yb(5)A(12)Sb(6) has an anisotropic structure with infinite anionic double chains cross-linked by Yb2+ ions. Polycrystalline ingots of Yb(5)A(12)Sb(6) prepared in the presence of 0.5 mol equiv of Ge showed room-temperature conductivity, thermopower, and thermal conductivity of similar to 1100 S/cm, similar to 20 mu V/K, and similar to 3.8 W/m . K, respectively. Investigations of other solid solutions of Yb(5)A(12)Sb(6), doping effects, and chemical modifications are discussed. Sr only partially replaces Yb in the structure leading to Sr0.85Yb4.15Al2Sb6. Electronic structure calculations performed using a highly precise full-potential linearized augmented plane wave method within the density functional theory scheme show the presence of a negative band gap and suggest incomplete electron transfer and a metallic character to the compound.