title: High-temperature phase transitions, spectroscopic properties, and dimensionality reduction in rubidium thorium molybdate family.
abstract: Four new rubidium thorium molybdates have been synthesized by high-temperature solid-state reactions. The crystal structures of Rb8Th(MoO4)6, Rb2Th(MoO4)3, Rb4Th(MoO4)4, and Rb4Th5(MoO4)12 were determined using single-crystal X-ray diffraction. All these compounds construct from MoO4 tetrahedra and ThO8 square antiprisms. The studied compounds adopt the whole range of possible structure dimensionalities from zero-dimensional (0D) to three-dimensional (3D): finite clusters, chains, sheets, and frameworks. Rb8Th(MoO4)6 crystallizes in 0D containing clusters of [Th(MoO4)6](8-). The crystal structure of Rb2Th(MoO4)3 is based upon one-dimensional chains with configuration units of [Th(MoO4)3](2-). Two-dimensional sheets occur in compound Rb4Th(MoO4)4, and a 3D framework with channels formed by thorium and molybdate polyhedra has been observed in Rb4Th5(MoO4)12. The Raman and IR spectroscopic properties of these compounds are reported. Temperature-depended phase transition effects were observed in Rb2Th(MoO4)3 and Rb4Th(MoO4)4 using thermogravimetry-differential scanning calorimetry analysis and high-temperature powder diffraction methods.
authors.affiliation: Institute for Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH , 52428 Jülich, Germany.
authors.forename: Bin
authors.initials: B
authors.lastname: Xiao
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Gesing
authors.forename: Philip
authors.initials: P
authors.lastname: Kegler
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Modolo
authors.forename: Dirk
authors.initials: D
authors.lastname: Bosbach
authors.forename: Hartmut
authors.initials: H
authors.lastname: Schlenz
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Suleimanov
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Alekseev