Syntheses, Crystal Structures, Resistivity Studies, and Electronic Properties of Three New Barium Actinide Tellurides: BaThTe4, BaUTe4, and BaUTe6

The three new solid-state compounds BaThTe4, BaUTe4, and BaUTe6 have been synthesized and characterized. BaThTe4 and BaUTe4 are isostructural. The structure consists of infinite ∞2[AnTe42–] layers separated by Ba2+ ions. Each An (An = Th, U) atom is coordinated to eight Te atoms in a bicapped trigonal-prismatic arrangement. Te atoms are connected to each other to form linear infinite chains. These Te–Te interactions are longer than that of a Te–Te single bond. However, this structure also possesses Te–Te single bonds. Charge balance in the formula BaAnTe4 may be achieved with [Ba2+]2[(An4+)2­(Te2–)2(Te22–)­(Te23–)2]4–. The structure of BaUTe6 features one-dimensional anionic ∞1[UTe62–] chains that are separated by Ba2+ ions. There are three Te–Te single bonds around each U atom. The anion in this structure can thus be described as [U4+(Te22–)3]2–. Resistivity measurements on single crystals of BaThTe4 and BaUTe6 show semiconducting behavior. DFT calculations indicate finite band gaps for BaThTe4 and for BaUTe6, whereas BaUTe4 has a vanishing density of states at the Fermi level.