Crystal structure of Ca{sub 5}Nb{sub 5}O{sub 17}

Journal Article · Thu Sep 15 04:00:00 EDT 2005 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2005.07.007· OSTI ID:20729104

Guevarra, J ^[1]; Smaalen, S van ^[1]; Rotiroti, N ^[1]; Paulmann, C ^[2]; Lichtenberg, F ^[3]

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1. Lehrstuhl fuer Kristallographie, Universitaet Bayreuth, Universitaetsstrasse 30, D-95440 Bayreuth (Germany)
2. Mineralogisch-Petrographisches Institut, Universitaet Hamburg, Grindelalle 48, D-20146 Hamburg (Germany)
3. Institut fuer Physik, EKM, Experimentalphysik VI, Universitaet Augsburg, Universitaetsstrasse 1, D-86135 Augsburg (Germany)

The crystal structure of Ca{sub 5}Nb{sub 5}O{sub 17}, an n=5 member of the homologous series A{sub n}B{sub n}O{sub 3n+2}, at room temperature has been determined by single-crystal X-ray diffraction using synchrotron radiation with a CCD area detector. The structure is monoclinic with spacegroup P2{sub 1}/c (b unique) and lattice parameters a=7.7494(3) A,b=5.4928(1) A,c=32.241(1) A,and {beta}=96.809(4){sup o}. It consists of perovskite-like slabs of corner-sharing NbO{sub 6} octahedra separated by an interslab region, where the octahedra on opposite sides of the gap do not share oxygen atoms resulting in an extra layer of oxygen atoms with respect to the ideal perovskite structure. The slabs are five octahedra wide. Ca atoms within the slabs occupy 12-fold coordinated sites whereas those at the borders show irregular coordination environments. The distortion of the octahedra increases from the center to the borders of the slabs. The computed valences for the Nb ions are very close to 5 at the borders while smaller values were obtained for sites in the middle of the slabs which suggests that the electrical conduction takes place predominantly in the middle of the slabs.

• OSTI ID: 20729104
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 9 Vol. 178; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CALCIUM COMPOUNDS
LATTICE PARAMETERS
LAYERS
MONOCLINIC LATTICES
NIOBIUM COMPOUNDS
NIOBIUM IONS
OXIDES
PEROVSKITE
SYNCHROTRON RADIATION
TEMPERATURE RANGE 0273-0400 K
TWINNING
X-RAY DIFFRACTION