title: Rb2REGaSi4O12 (RE = Y, Eu, Gd, Tb): luminescent mixed-anion double layer silicates containing chains of edge-sharing REO7 pentagonal bipyramids.
abstract: Four new rare earth gallosilicates, Rb 2REGaSi4O12 (RE = Y, Eu, Gd, and Tb, denoted as REGS-1), have been synthesized under high-temperature, high-pressure hydrothermal conditions and characterized by single-crystal X-ray diffraction. They are the first examples of rare earth gallosilicates that contain individually occupied tetrahedral Ga(3+) and Si(4+) centers. The unique structure is formed of two 1D and one 2D substructural units: unbranched achter single chains which are seldom observed in silicates, the PaCl 5-type infinite chains formed of edge-sharing REO7 petagonal bipyramids and the unprecedented mixed-anion double layers with the composition [GaSi4O12]. The photoluminescence properties of EuGS-1 and TbGS-1 have been studied. The Y(3+) ion in YGS-1 can be partially replaced by Eu(3+) and Tb(3+) to yield luminescent materials.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, ROC.
authors.forename: Cheng-Shiuan
authors.initials: CS
authors.lastname: Lee
authors.forename: Yueh-Chun
authors.initials: YC
authors.lastname: Liao
authors.forename: Jung-Tsung
authors.initials: JT
authors.lastname: Hsu
authors.forename: Sue-Lein
authors.initials: SL
authors.lastname: Wang
authors.forename: Kwang-Hwa
authors.initials: KH
authors.lastname: Lii