FTIR measurements for structural probing of rare-earth sol-gel silica glass system co-doped with Al3+

The Al co-doping in silica matrix doped with rare earth (RE) namely Er³⁺, Ho³⁺ and Eu³⁺ ions have been studied. The Al co-doping enhances the emission properties of the Sol-Gel glass doped RE samples. FTIR measurements have been used in this study to probe the aluminum´s behavior inside the silica network. The FTIR absorption bands 462.2, 810, 1103 cm^-1 of the Si-O-Si and 685, 786 cm^-1 of the Al-O bands have been used as principle absorption bands to explain the effect of increasing the Al :RE molar ratios, 4, 8, 10,as well as without Al co-dopant, on the doping process. The emission spectra of the prepared samples supported some concepts of the mechanism of aluminum action as co-dopant in the sol-gel silica matrices. The emission bands due to the (⁴I_13/2 →⁴I_15/2 ~nm) , ( ⁵D₂→⁵I₇ ~753 nm) and ( ⁵D₀→⁷F₂ ~619 nm) transitions of Er³⁺, Ho³⁺ and Eu³⁺ ions, respectively , have been enhanced at Al :RE molar ratio of 10 comparing with 4 and 8. In contrast, the case of without Al co-doping shows strong quenched in these transitions.