Publication: Rearrangement in the local, electronic and crystal structure of europium titanates under reduction and oxidation
Дата
2020
Авторы
Khramov, E. V.
Svetogorov, R. D.
Kurilkin, V. V.
Murzin, V. Y.
Popov, V. V.
Menushenkov, A. P.
Molokova, A. Y.
Ivanov, A. A.
Rudakov, S. G.
Boyko, N. V.
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Аннотация
© 2020 Elsevier B.V.We studied powder samples of europium titanates Eu1−x 2+Eux 3+TiO3+x/2 prepared by sol-gel and coprecipitation methods with subsequent thermal treatment of precursors at different conditions (reducing or oxidizing atmosphere, temperature, exposure time). We have revealed a radical rearrangement in the local, electronic and crystal structure of europium titanates depending on synthesis conditions. The combination of synchrotron X-ray diffraction (s-XRD), X-ray absorption (XANES and EXAFS), infrared and Raman spectroscopies supplemented by photoluminescence and simultaneous thermal analysis was used in our study. It is shown that the combined XANES and thermogravimetric analysis gives clear evidence of a change in the oxidation state of europium cations from Eu2+ to Eu3+. The comparison of s-XRD, XANES, and EXAFS data allowed us to explain the local structure rearrangement during the phase transition from cubic perovskite Eu2+TiO3 (space group Pm3¯m) to pyrochlore phase Eu2 3+Ti2O7 (space group Fd3¯m) through intermediate layered perovskite Eu2 3+Ti2O7 with monoclinic structure (space group P21) under annealing in oxidizing atmosphere. The Raman spectroscopy study pointed to significant changes in the local structure of the anionic sublattice upon the observed phase transitions. The analysis of luminescence spectra has shown that Eu3+ cations occupy positions with low local site symmetry in all synthesized compounds regardless of the type of the crystal structure.
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Rearrangement in the local, electronic and crystal structure of europium titanates under reduction and oxidation / Khramov, E.V. [et al.] // Journal of Alloys and Compounds. - 2020. - 831. - 10.1016/j.jallcom.2020.154752
URI
https://www.doi.org/10.1016/j.jallcom.2020.154752
https://www.scopus.com/record/display.uri?eid=2-s2.0-85082508605&origin=resultslist
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https://openrepository.mephi.ru/handle/123456789/20459
https://www.scopus.com/record/display.uri?eid=2-s2.0-85082508605&origin=resultslist
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS_CPL&DestLinkType=FullRecord&UT=WOS:000531726800009
https://openrepository.mephi.ru/handle/123456789/20459