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) - Popov, V.V.
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.