High-Pressure Synthesis, Structure, and Electrical Property of Iodine-Filled Skutterudite I_0.9Rh₄Sb₁₂—First Anion-Filled Skutterudite

An iodine containing skutterudite compound I 0.9 Rh 4 Sb 12 was prepared by the reaction of the element mixture with an iodine excess composition (I:Rh:Sb = 1.5:4:12) at 5−12 GPa and 850 °C. Rietveld structural analysis revealed that this is the first anion-filled skutterudite crystallizing in the space group I m-3 with a lattice constant of a = 9.29997(6) Å. X-ray photoelectron spectroscopy proved the oxidation state of iodine to be I − . The compound is semimetallic with a resistivity of 9.9 mΩcm at 300 K. Band structure and density of states calculations suggested that the bands near the Fermi level are mainly composed of Rh-p, Rh-d, and Sb-p orbitals; the contribution of iodine is not large.