Abstract
Nioboaeschynite-(Ce), ideally Ce(NbTi)O6 [cerium(III) niobium(V) titanium(IV) hexa-oxide; refined formula of the natural sample is Ca 0.25Ce0.79(Nb1.14Ti0.86)O 6], belongs to the aeschynite mineral group which is characterized by the general formula AB2(O,OH)6, where eight-coordinated A is a rare earth element, Ca, Th or Fe, and six-coordinated B is Ti, Nb, Ta or W. The general structural feature of nioboaeschynite-(Ce) resembles that of the other members of the aeschynite group. It is characterized by edge-sharing dimers of [(Nb,Ti)O6] octa-hedra which share corners to form a three-dimensional framework, with the A sites located in channels parallel to the b axis. The average A-O and B-O bond lengths in nioboaeschynite-(Ce) are 2.471 and 1.993 Å, respectively. Moreover, another eight-coordinated site, designated as the C site, is also located in the channels and is partially occupied by A-type cations. Additionally, the refinement revealed a splitting of the A site, with Ca displaced slightly from Ce (0.266 Å apart), presumably resulting from the crystal-chemical differences between the Ce 3+ and Ca2+ cations.
Original language | English (US) |
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Pages (from-to) | i64-i65 |
Journal | Acta Crystallographica Section E: Structure Reports Online |
Volume | 68 |
Issue number | 8 |
DOIs | |
State | Published - Aug 2012 |
Externally published | Yes |
Keywords
- R factor = 0.023
- T = 293 K
- data-to-parameter ratio = 16.1
- disorder in main residue
- mean σ(Nb-O) = 0.002Å
- single-crystal X-ray study
- wR factor = 0.055
ASJC Scopus subject areas
- General Chemistry
- General Materials Science
- Condensed Matter Physics