Synthesis, FT-IR and X-ray diffraction investigations of gadolinium-substituted pyrochlore oxide Gd_(1.82)Cs_(0.18)Ti_2O_(6.82) via a sol-gel process

摘要

Novel pyrochlore oxides Gd_(1.82)Cs_(0.18)Ti_2O_(6.82) has been synthesized using the sol-gel process from the titanium alkoxide Ti(OR)_4 and two ultra pure oxides Cs_2CO_3 and Gd_2O_3. Pure acetic acid was used as mutual solvent. This carboxylic acid does not act only as an acid catalyst, but also as ligand modifying the whole hydrolysis condensation process. The effect of heat treatment, to eliminate the organic material from xerogel was investigated by FT-IR spectroscopy. Based on thermal gravimetric (TG) and differential scanning calorimetric (DSC) analysis results, we suggest that thermal decomposition of the xerogel takes place in three major steps. 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. Crystal structure of oxygen deficient pyrochlore, Gd_(1.82)Cs_(0.18)Ti_2O_(6.82) calcinated at 1000 deg C, was determined using the Rietveld method. It was found that the sample crystallise in the cubic symmetry with Fdim space group and with a lattice parameter a = 10.1835 (4) A. The oxygen vacancies in this compound are randomly distributed over the O' sites. Conductivity in this material, which is an anionic conductor, results of migration of oxygen vacancies into the conduction pathways.