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

Abstract

Abstract We report a comparative study of Ln2M2O7 (Ln\u202f=\u202fGd, Tb, Dy; M\u202f=\u202fTi, 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 Ln2M2O7 such as splitting of Ln-O coordination shells and changes of the symmetry in local environment.