A two-step ion exchange route to the new metastable double-layered perovskite, (RbNa){sub 1{minus}x}Ca{sub x/2}LaNb{sub 2}O{sub 7} (x {approx} 0.9)

Journal Article · Fri Jan 15 04:00:00 EST 1999 · Materials Research Bulletin

DOI:https://doi.org/10.1016/S0025-5408(99)00009-4· OSTI ID:352421

Cushing, B L; Wiley, J B ^[1]

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1. Univ. of New Orleans, LA (United States)

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.

• OSTI ID: 352421
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 2 Vol. 34; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM OXIDES
CRYSTAL STRUCTURE
ION EXCHANGE
LANTHANUM OXIDES
LATTICE PARAMETERS
NIOBIUM OXIDES
RUBIDIUM OXIDES
SODIUM OXIDES
SYNTHESIS
X-RAY DIFFRACTION