New phases of K, Eu-silicate in the family of compounds with the orthorhombic pellyite-like unit cellстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The structures of three phases of the synthesized europium potassium silicate were determined by X-ray diffraction. Two of these phases crystallize in a new structural type. The chemical formulas of the phases were determined. The orthorhombic unit-cell parameters of all three phases are equal: a = 14.852(1) angstrom, b = 15.902(1) angstrom, c = 7.243(1) angstrom, sp. gr. P2(1)2(1)2 (phase I) and sp. gr. Pbam (phases II and III). The structures were solved by direct methods and refined from X-ray diffraction data collected from one crystal to R = 0.0271, 0.0479, and 0.0582 based on 4370, 3320, and 2498 reflections, respectively, with vertical bar F vertical bar > 3 sigma(F). The crystalchemical formulas of the phases (Z=4) are K(3)Eu(3+)[Si(6)O(15)](center dot)2H(2)O, K(3)Eu(3+)[Si(6)O(13)(OH)(4)](center dot)2H(2)O, and K(3)Eu(3+)[Si(4)O(9.5)(OH)](OH)(2 center dot) 5.5H(2)O. The structure of phase I consists of silicon-oxygen sheets [Si(6)O(15)] analogous to those found in the isostructural compound K(3)Nd[Si(6)O(15)]center dot 2H(2)O. In the structures of phases II and III, the ribbons [Si(6)O(17)] and [Si(8)O(21)] run along the shortest c axis and are linked together by Eu(3+) octahedra and trigonal prisms to form three-dimensional layered and framework structures containing K atoms between the sheets and in the channels.