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van Smaalen, Sander ; Dinnebier, Robert E. ; Katzke, Hannelore ; Depmeier, Wulf:
Structural Characterization of the High-Temperature Phase Transitions in Ca₈[Al₁₂O₂₄](MoO₄)₂Aluminate Sodalite Using X-ray Powder Diffraction.
In: Journal of Solid State Chemistry.
Bd. 129
(1997)
Heft 1
.
- S. 130-143.
ISSN 0022-4596
DOI: https://doi.org/10.1006/jssc.1996.7251
Abstract
The structures are reported of the room-temperature and the three high-temperature phases of Ca8Al12O24(MoO4)2aluminate sodalite CAM. Structure refinements have been performed with the Rietveld method using synchrotron radiation X-ray powder diffraction data. The cubic phase has symmetryI43mwitha=9.29377(4) Å. The tetragonal phases have symmetryP4c2, and their unit cells corresponds to a2a×2a×csupercell of the cubic phase. The second tetragonal phase (T2) exists for 614<T<624 K and has lattice parametersa=13.14536(6) Å andc=9.29224(8) Å. The first tetragonal (T1) phase is stable for 590<T<614 K and has lattice parametersa=13.12263(5) Å andc=9.32081(5) Å, The orthorhombic phase has symmetryAba2 witha=26.14683(8) Å,b=13.07061 Å, andc=9.31413(2) Å. The transition (on decreasing temperatures) atTc≈624 K, from the cubic to the T2 phase, is of second order and is found to be related to change in the orientational order of the cage anions MoO2−4. The T2 to T1 transition atTc≈614 K is of first order, and it corresponds to a displacement of the cage anions to an off-center position in the cages, while keeping orientational disorder over at least two orientations. The transition atTc≈590 K, from the T1 phase to the orthorhombic phase, is again a first-order transition, and it is related to a complete ordering of the cage anions. A detailed description is given of the structural distortions of the framework, accompanying the phase transitions.
Weitere Angaben
| Publikationsform: | Artikel in einer Zeitschrift |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Mathematik, Physik und Informatik > Fachgruppe Materialwissenschaften > Lehrstuhl Kristallographie Fakultäten Fakultäten > Fakultät für Mathematik, Physik und Informatik Fakultäten > Fakultät für Mathematik, Physik und Informatik > Fachgruppe Materialwissenschaften |
| Titel an der UBT entstanden: | Ja |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 530 Physik |
| Eingestellt am: | 15 Jun 2016 08:55 |
| Letzte Änderung: | 15 Jun 2016 08:55 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/32683 |