Synthesis, X-ray diffraction investigations and spectroscopic analysis of yttrium-substituted pyrochlore oxides Y2−2xBi2xTi2O7 via a sol–gel process

Solid solutions of Y2−2xBi2xTi2O7 pyrochlores oxides in the YCl3–Ti(OR)4–Bi2O3 system were synthesized using sol–gel technique. Two protocols have been investigated. Calcination at 1000 °C of two gels CEN and DRY obtained by centrifugation and dryness, respectively, gives rise to different compositions of the pyrochlore phases. The effect of heat treatment to eliminate the organic material from xerogels was investigated by high temperature X-ray diffraction (HTXRD), thermal gravimetric (TG) and differential thermal analysis (DTA).Refinement results confirm a cubic structure with Fd3m space group. A gradual increase of the lattice parameter with increasing x is observed. Crystal structure analysis revealed that substitution of Bi3+ onto the Y3+ sites in the pyrochlore oxide Y2−2xBi2xTi2O7 results in a decrease of Ti–O bond.The IR spectra confirm the substitution of Y3+ by Bi3+ in the pyrochlore structure. Raman results suggest that when Bi3+ is invoked in the structure, slight shifts of the vibrational frequencies and peak splitting are observed.