Soft chemical synthesis and structural characterization of Y2HfxTi2−xO7

A novel soft chemistry route was developed to synthesize Y2HfxTi2−xO7 (0≤x≤2.0) oxide solid solution. An aqueous solution containing reactants was produced to ensure the combustion reaction taking place at the molecular level. A suite of characterization techniques, including X-ray diffraction, Raman, transmission electron spectroscopy, as well as X-ray absorption near edge structure (XANES), is employed to investigate the structural and phase changes of the series. Both X-ray and electron diffraction patterns show that the Y2HfxTi2−xO7 system undergoes a clear composition-induced phase transition from ordered pyrochlore to disordered defect-fluorite at x~1.5. On the other hand, Raman and XANES spectra reveal a gradual evolution of the local structure with the substitution of Hf for Ti.