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Geisler, T., Popa, K., Konings, R. J. M. & Popa, A. F. (2006) A Raman spectroscopic study of the phase transition of BaZr(PO4)(2): Evidence for a trigonal structure of the high-temperature polymorph. J. Solid State Chem. 179 1490–1496.
Added by: Florent Boucher (2016-05-12 13:21:37) |
| Type de référence: Article DOI: 10.1016/j.jssc.2006.01.065 Numéro d'identification (ISBN etc.): 0022-4596 Clé BibTeX: Geisler2006 Voir tous les détails bibliographiques  |
Catégories: CESES Mots-clés: barium zirconium diorthophosphate, barium zirconium phosphates, BaZr(PO4)(2), crystal-structure, phase transition, phosphates, Raman spectroscopy, spectrum Créateurs: Geisler, Konings, Popa, Popa Collection: J. Solid State Chem. |
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We have studied the structural evolution of monoclinic BaZr(PO4)(2) during heating up to 835 K by Raman spectroscopy. In agreement with previous studies we found a first-order phase transition at about 730 K during heating while upon cooling the reverse transition occurs at 705 K. However, some disagreement about the crystal structure of the high-temperature polymorph occurs in the literature. While the space group has not yet been determined, the X-ray diffraction pattern of the high-temperature phase has been indexed on either an orthorhombic or a hexagonal unit cell. We found that the number of Raman active internal PO4 vibrational modes decrease from nine to six during the transition. A group theoretical survey through all orthorhombic, trigonal, and hexagonal factor groups revealed that the observed number of vibrations would only be consistent with the Ba and Zr atoms located at a D-3d((3) over barm) site, the P and two O atoms at a C-3p(3m), and six O atoms at a C-s(m) site in the D-3d factor group. Based on our Raman data, the space group of the high-temperature polymorph is thus either D-3d(1)(P(3$) over bar $ 1m), D-3d(3)(P(3) over bar $ m1), or D-3d(5)(R(3) over bar m). (C) 2006 Elsevier Inc. All rights reserved.
Added by: Florent Boucher |