Study of rehydration process of alumina containing cerium doped silica gels by ultraviolet, visible and FTIR spectroscopy

Alumina containing Ce doped silica xerogel and glasses were prepared by sol -gel processing at 500-1000 degrees C under oxygen atmosphere. The partiall y densified gels were kept at 80% relative humidity for ageing and spectros copic properties of the rehydrated partially densified gels were mainly stu died by absorption and FTIR spectroscopy. With ageing time the generation o f absorption bands of Ce3+ ions suggested the change of local symmetry of t he Ce ions. Finally, fourfold splitting was observed for Ce3+ after 60 days indicating eight co-ordinated water complexes like dodecaheral complexes h aving symmetry group D-2d.