Comparative analysis of long- and short-range structures features in titanates Ln2Ti2O7 and zirconates Ln2Zr2O7 (Ln = Gd, Tb, Dy) upon the crystallization process. (July 2019)

• Record Type: Journal Article
• Authors: Popov, V.V.; Menushenkov, A.P.; Ivanov, A.A.; Gaynanov, B.R.; Yastrebtsev, A.A.; d'Acapito, F.; Puri, A.; Castro, G.R.; Shchetinin, I.V.; Zheleznyi, M.V.; Zubavichus, Ya.V.; Ponkratov, K.V.
• Is Part Of: Journal of physics and chemistry of solids. Volume 130(2019)
• Page Start: 144
• Page End: 153
• Publication Date: 2019-07
• Subjects: oxides -- Phase transitions -- X-ray diffraction -- XAFS (EXAFS and XANES) -- Raman spectroscopy; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2019.02.019
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: We report a comparative study of Ln 2 M 2 O7 ( Ln = Gd, Tb, Dy; M = Ti, Zr) synthesized by combination of the sol-gel and coprecipitation methods followed by calcination at elevated temperatures. The long-range average crystal as well as short-range local structure in the samples were analyzed using X-ray diffraction, X-ray absorption spectroscopy (XAFS) and Raman spectroscopy. It has been found that Ln -Ti precursors crystallize directly to pyrochlore phase, whereas crystallization of Ln -Zr precursors to pyrochlore phase goes through intermediate fluorite phase. We have shown that X-ray absorption data make possible to detect the crystallization and phase transition features in Ln 2 M 2 O7 such as splitting of Ln -O coordination shells and changes of the symmetry in local environment. Graphical abstract: Image 1 Highlights: Crystallization and phase transitions in Ln 2 M 2 O7 ( Ln = Gd, Tb, Dy; M = Ti, Zr) were studied. K -Ti pre-edge region of XANES spectra is very sensitive to Ln 2 Ti2 O7 crystallization. The shape of the Ln L 3 -XANES spectra is sensitive to pyrochlore phase formation. Formation of a pyrochlore structure causes the splitting of Ln -O shell in EXAFS-FT.