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Author Cushing, B. L. ♦ Wiley, J. B.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ CRYSTAL STRUCTURE ♦ SYNTHESIS ♦ RUBIDIUM OXIDES ♦ SODIUM OXIDES ♦ CALCIUM OXIDES ♦ LANTHANUM OXIDES ♦ NIOBIUM OXIDES ♦ X-RAY DIFFRACTION ♦ LATTICE PARAMETERS ♦ ION EXCHANGE
Abstract A new metastable double-layered perovskite, Rb{sub 0.04}Na{sub 0.08}Ca{sub 0.44}LaNb{sub 2}O{sub 7}, has been synthesized by a two-step ion exchange route. Initially, RbLaNb{sub 2}O{sub 7} is reacted to produce the known metastable phase NaLaNb{sub 2}O{sub 7}; then this is exchanged with calcium to yield the title compound. The product has neither the RbLaNb{sub 2}O{sub 7} nor NaLaNb{sub 2}O{sub 7} structure types, but converts to a superstructure of KLaNb{sub 2}O{sub 7} with an orthorhombic unit cell: a = 3.885(1), b = 7.725(2), and c = 20.884(4) {angstrom}. Direct calcium exchange of RbLaNb{sub 2}O{sub 7} results in poorly crystalline products with only 31% exchange, while exchange with KLaNb{sub 2}O{sub 7} shows little evidence of reaction. The importance of size matching in divalent-for-monovalent cation exchange is discussed.
ISSN 00255408
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-01-15
Publisher Place United States
Journal Materials Research Bulletin
Volume Number 34
Issue Number 2


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