Optical properties of Europium doped gels during densification

Base catalyzed porous silica sol-gel monoliths fired at 1000 °C were used to prepare Eu and Eu-Al co-doped glasses by post doping and subsequent densification around 1125-1150 °C in air. Both Eu³⁺ and Eu²⁺ ions were found to coexist in densified Al co-doped glasses. The absorption, emission and excitation spectra of the Eu-doped glasses are significantly dependent on the alumina content. The densification temperature of the doped gel also played a major role in the reduction process. The UV excitation efficiency for the ⁵D₀→⁷F₂ transition of Eu³⁺ ions (614 nm) was increased in the presence of Eu²⁺ ions due to energy transfer from Eu²⁺ to Eu³⁺ ions.