Synthesis, Raman and X-ray diffraction investigations of rubidium-doped Gd1.8Ti2O6.7 pyrochlore oxide via a sol-gel process

Nanoparticles of rubidium-doped gadolinium titanates oxide were prepared by the sol-gel process from the titanium alcoxyde Ti(OBu)(4) and the two oxides Rb2CO3 and Gd2O3. Thermal gravimetric (TG) and differential thermal analysis (DTA) results suggest that thermal decomposition of the xerogel takes place when the xerogel is heated at 400 degrees C. X-ray powder diffraction (XRD) measurements were carried out to study the structure evolution of the sample and to determine the crystalline phases present after heat treatment. A well-crystallized single-phased nanopowder was obtained after calcination at 1000 degrees C. X-ray diffraction combined to the Raman analysis confirmed the powder's single-phase nature at this temperature. The Rb+ did not enter the pyrochlore crystal lattice to substitute Gd3+ or Ti4+ as shown by XRD and X-ray photoelectron spectroscopy (XPS). It is probably dispersed uniformly onto gadolinium titanate nanoparticles. Crystal structure of the non-stoichiometry pyrochlore Rb+-doped phase Gd1.8Ti2O6.7, was determined using the Rietveld method. Conductivity analysis shows that the presence of Rb+ dopant in Gd1.8Ti2O6.7 leads to an increase of the ionic conductivity compared to the non-doped Gd1.8Ti2O6.7. (c) 2007 Elsevier B.V. All rights reserved.