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Synthesis, Structure and Charge Transport Properties of Yb5Al2Sb6: A Zintl Phase with Incomplete Electron Transfer

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posted on 2009-06-01, 00:00 authored by Iliya Todorov, Duck Young Chung, Linhui Ye, Arthur J. Freeman, Mercouri G. Kanatzidis
We report the synthesis, structure, spectroscopic properties, charge and thermal transport, and electronic structure of a new member of the Zintl family, Yb5Al2Sb6. The compound crystallizes in the Ba5Al2Bi6 structure type and requires the addition of Ge or Si in the synthesis, which appears to act as a catalyst. Yb5Al2Sb6 has an anisotropic structure with infinite anionic double chains cross-linked by Yb2+ ions. Polycrystalline ingots of Yb5Al2Sb6 prepared in the presence of 0.5 mol equiv of Ge showed room-temperature conductivity, thermopower, and thermal conductivity of ∼1100 S/cm, ∼20 μV/K, and ∼3.8 W/m·K, respectively. Investigations of other solid solutions of Yb5Al2Sb6, 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.

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