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Title: Crystal structures and luminescence properties of novel compounds K{sub 4}M{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}] (M = Ce, Gd)

Two novel potassium rare earth silicates, obtained by hydrothermal synthesis, have been investigated by X-ray diffraction and described by the general formula K{sub 4}M{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}] (M = Ce, Gd). The parameters of the monoclinic K{sub 4}Ce{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}] and K{sub 4}Gd{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}] cells are, respectively, as follows: a = 26.867(1), 26.6520(2) A; b = 7.4150(2), 7.2854(1) A; c = 14.910(1), 14.8182(1) A; {beta} = 123.52(1) Degree-Sign , 123.46(1) Degree-Sign ; and sp. gr. P2{sub 1}/n. The structures are solved by the charge flipping method and refined in the anisotropic approximation of thermal vibrations for atoms to R = 5.2 and 2.5%, respectively. The compounds under study are crystallized into a new structural type, which is based on two-level [Al{sub 2}Si{sub 8}O{sub 24}] layers, combined into a three-dimensional framework by columns of edge-sharing seven-vertex REE polyhedra. Potassium atoms are located in the framework channels. The spectral luminescence characteristics are determined. The luminescence bands are typical of Gd{sup 3+} and Ce{sup 3+} ions. Upon excitation by light with {lambda}{sub exc} = 246 nm, a band due to the {sup 2}D {yields} {sup 8}F{sub 5/2} transition with {lambda}{sub max} = 430 nm is observed inmore » the spectrum of K{sub 4}Ce{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}] and a band related to the {sup 6}P{sub 7/2} {yields} {sup 8}S{sub 7/2} transition with {lambda}{sub max} = 311 nm is observed in the spectrum of K{sub 4}Gd{sub 2}[Al{sub 2}Si{sub 8}O{sub 24}].« less
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
  2. Russian Academy of Sciences, Fedorovsky All-Russian Research Institute of Mineral Resources (Russian Federation)
  3. Russian Academy of Sciences, Institute of Geochemistry, Siberian Branch (Russian Federation)
Publication Date:
OSTI Identifier:
22210424
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 58; Journal Issue: 6; Other Information: Copyright (c) 2013 Pleiades Publishing, Inc.; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; CERIUM IONS; EXCITATION; GADOLINIUM IONS; LAYERS; LUMINESCENCE; MONOCLINIC LATTICES; POTASSIUM; SILICATES; X-RAY DIFFRACTION