title: High-pressure synthesis and characterization of new actinide borates, AnB4O8 (An=Th, U).
abstract: New actinide borates ThB4O8 and UB4O8 were synthesized under high-pressure, high-temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker-type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single-crystal X-ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB4O8: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) Å(3); R1=0.0255, wR2=0.0653 (all data). Lattice parameters for UB4O8: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) Å(3); R1=0.0227, wR2=0.0372 (all data). The new AnB4O8 (An=Th, U) structure type is constructed from corner-sharing BO4 tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold-coordinated. The actinide cations are located between the boron-oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.
authors.affiliation: Institute of General, Inorganic and Theoretical Chemistry, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck (Austria), Fax: (+43) 512-507-57099.
authors.forename: Ernst
authors.initials: E
authors.lastname: Hinteregger
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hofer
authors.forename: Gunter
authors.initials: G
authors.lastname: Heymann
authors.forename: Lukas
authors.initials: L
authors.lastname: Perfler
authors.forename: Florian
authors.initials: F
authors.lastname: Kraus
authors.forename: Hubert
authors.initials: H
authors.lastname: Huppertz
keywords: Raman spectroscopy; actinides; borates; density functional theory; high-pressure chemistry