Spectroscopic studies of mixed pyrochlore-oxide (Y/Gd)2Ti2O7 samples prepared via sol–gel and solid-state methodologies and calcined at different temperatures

Mixed pyrochlore-oxide (Y/Gd)2Ti2O7 samples were prepared via different processes, namely by the use of a sol–gel synthetic methodology and also by a solid-state reaction. Their characterisation was performed by XRD, Micro-Raman, XPS and Laser-Induced Luminescence studies. According to the XRD, Micro-Raman and XPS results, powder composition seems to depend strongly on the synthetic processes and calcination temperature. The effective optical absorption edge of the prepared samples shifts to shorter wavelength with the temperature increase. Therefore the introduction of Gd3+ or Y3+ in the pyrochlore structure is not the predominant factor in the preparation protocol, the calcination temperature playing the major role. Luminescence studies showed that Gd3+ or Y3+ presence and high calcination temperatures induce the formation of emissive sites in the pyrochlore, responsible for a new emission band maximising at ca. 767 nm which is much reduced for lower annealing temperatures.