Blue light emission from Eu2+ ions in sol–gel-derived Al2O3–SiO2 glasses

Blue light-emitting glasses were successfully prepared by doping Eu2+ ions in the system Al2O3–SiO2. The Al2O3–SiO2 glasses doped with Eu3+ ions were synthesized using a sol–gel method, followed by heating in hydrogen gas atmosphere to reduce into the Eu2+ ions. The obtained glasses exhibited emission spectra with peak at ∼450 nm due to 4f65d→4f7 (8S7/2) transition, the intensities of which strongly changed depending on their glass composition and heating conditions. The emission quantum efficiency of 48% was achieved by heating the glass with the ratio of Al3+ to Eu3+ at about 6 at 1000 °C in hydrogen gas atmosphere. It was found that the Al2O3–SiO2 glasses were appropriate not only for homogeneously doping the Eu3+ ions in glass structure but also reducing to Eu2+ ions, resulting in enhanced blue light-emission properties.