Annealing effect on photoluminescence properties of Er doped Al2O3–SiO2 sol–gel films

Annealing effect on photoluminescence intensity of Er doped Al2O3–SiO2 prepared from Er doped boehmite (AlOOH) and GPS (3-glycidoxypropyltrimethoxysilane) hybrid was investigated. The emission intensities peaked at 1.54 μm, which correspond to the 4I13/2 → 4I15/2 transition of the Er3+ ion, are greatly increased by about 8 times between 900 and 1000 °C, than that expected from TGA associated with the elimination of hydroxyl groups which is responsible for the fluorescence quenching. The residual hydroxyl groups for Er doped Al2O3–SiO2 after annealing at high temperature was further analyzed by FT-IR. Finally, fluorescence intensities were compared with the variation of BET surface areas against the annealing temperature. It was found that photoluminescence intensity below 1000 °C was more dependent on surface hydroxyl groups re-adsorbed by a high specific surface area rather than internal hydroxyl groups remained in gel film.