Crystal structures and temperature-induced phase transitions of Sr2Mn(2+)W(6+)O6, and of its transformation to Sr2Mn(3+)W(6+)O(6+δ)
| Autor: | Faik, A., Igartua, J. M., Cuello, G. J., Jiménez-Villacorta, Félix, Castro, Germán R., Lezama, Luis |
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| Jazyk: | angličtina |
| Rok vydání: | 2009 |
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| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | 10 pages, 9 figures, 3 tables.-- Printed version published Sep 17, 2009. We present a new effective method for synthesizing Sr2MWO6 double perovskite oxides: the co-precipitation route at 1220 K in nitrogen environment. Using conventional X-ray diffraction methods, we have confirmed the room-temperature space group of Sr2Mn(2+)WO6 to be P2(1)/n: Z = 2; a=5.6764(1)Ǻ; b=5.6752(1)Ǻ; c=8.0149(1)Ǻ; β=90.12(1)Ǻ and V=258.18(1)Å3. We show that the compound presents the following temperature induced phase-transition sequence: P2(1)/n -> I4/m -> Fm3m. After a thermal treatment, 24 h at 870 K in air, the Sr2Mn(2+)WO6 compound transforms irreversibly to Sr2Mn(3+)WO(6+δ). This transformation has been confirmed by EPR and XANES measurements. Using conventional X-ray diffraction methods, we have shown the room-temperature space group of Sr2Mn(3+)WO(6+δ) to be I4/m: Z = 2; a=5.6353(1)Ǻ; c=8.0149(1)Ǻ and V=254.53(1)Å3. We show that the compound presents the following temperature induced phase-transition sequence: I4/m(->I4/mmm) -> Fm3m. The tetragonal-to-tetragonal phase transition is suggested to be present, it is not observed as it is very weak; it is attributed to the presence of the Jahn-Teller active Mn3+ cation. This work was done in part under Project Nos.: UPV 0063.310-13564/2001-2007 and MAT2008-05839/MAT. The authors thank the Spanish Ministry of Science for the beamtime allocation and the staff of Spanish CRG beamline (SpLine-BM25) of ESRF for their support during the experiment. |
| Databáze: | OpenAIRE |
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