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.