Lithium as an Interstitial Donor in Bismuth and Bismuth–Antimony Alloys

Abstract

Band structure calculations show that substitutional lithium in bismuth can form sharp density of states peaks close to the Fermi energy, suggesting the presence of a resonant level, whereas interstitial lithium is expected to act as a simple donor impurity. Experimentally, polycrystalline elemental bismuth samples doped with 0.3%, 0.7%, 1.5%, 3%, 14% (a eutectic composition between Bi and the tetragonal intermetallic compound BiLi), and 20% lithium were prepared. Single-crystal and polycrystalline Bi88Sb12 samples were also doped with lithium. The thermal and thermoelectric transport data of those compounds are reported. The data are consistent with lithium being a donor, leading to the conclusion that it is an interstitial impurity. The thermal conductivity of Bi decreases with Li content at low concentrations, but that of the Bi/BiLi eutectic composition shows the highest value.