Microstructural characterization and phase analysis of new pyrochlore-type mixed metal oxides RESmTi2O7 (RE = Gd, Er) by X-ray powder diffraction using Rietveld refinement method and spectroscopic studies

Two new RESmTi2O7 mixed metal oxides were prepared by mixing Sm2O3, RE2O3 (RE = Gd, Er) and TiO2 using a modified solid state method which gives the target pyrochlores with excellent phase purity. SmGdTi2O7 and SmErTi2O7 samples were characterized using PXRD, SEM, EDS, FT-IR and Raman spectroscopy. Rietveld refinement was employed to obtain crystallographic parameters using MAUD software. The qualitative phase analysis showed that the mixed metal oxides were crystallized in a cubic crystal system with the Fd3m space group with small shifting in Bragg positions due to the effect of RE cationic radius on the lattice structure. The quantitative phase analysis using Rietveld refinement method illustrated the relation between crystallographic parameters, structural factors and ionic radii of RE atoms, during which, the sensitivity of the pyrochlores for cationic radius variations of RE atoms, and the extraordinary effect of the RE on the crystal structure of pyrochlores were confirmed.