title: Mild hydrothermal crystal growth, structure, and magnetic properties of ternary U(IV) containing fluorides: LiUF5, KU2F9, K7U6F31, RbUF5, RbU2F9, and RbU3F13.
abstract: Single crystals of several ternary alkali uranium fluorides, LiUF5, KU2F9, K7U6F31, RbUF5, RbU2F9, and RbU3F13, have been obtained in a mild hydrothermal process using UO2(CH3CO2)2(H2O)2 as the uranium source. Their crystal structures were determined by single crystal X-ray diffraction. The uranium in the starting reagent was successfully reduced from U(6+) to U(4+) in a dilute hydrofluoric acid environment, aided by the presence of a copper salt. All materials exhibit highly complex crystal structures that range from two-dimensional to three-dimensional. The U(4+) cations are found in high (UF8 and UF9) coordination environments. The magnetic susceptibility measurements yielded effective magnetic moments of 3.01-3.83 μB for the U(4+) cations. The temperature dependent magnetic susceptibility measurements confirmed that the U(4+) cation exhibits a nonmagnetic singlet ground state at low temperatures. No long-range magnetic order was observed for any of the above compositions down to 2 K. Optical and thermal behaviors of the fluorides were also investigated.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Jeongho
authors.initials: J
authors.lastname: Yeon
authors.forename: Mark D
authors.initials: MD
authors.lastname: Smith
authors.forename: Joshua
authors.initials: J
authors.lastname: Tapp
authors.forename: Angela
authors.initials: A
authors.lastname: Möller
authors.forename: Hans-Conrad
authors.initials: HC
authors.lastname: zur Loye