Observation of tunable persistent luminescence in XAl2O4: Eu2+ (X=Ca, Sr) doped borate glass for efficient optical information storage

Eu2+ doped XAl2O4 (X = Ca, Sr) phosphor is usually prepared to study the monochromatic afterglow emission in a single crystal field, but the tunable afterglow emission with multiple emission bands in polycrystal fields has hardly been explored. In this paper, by fine-tuning the ratio of calcium carbonate to strontium carbonate in the borate matrix, Eu2+ ions are introduced into CaAl2O4 and SrAl2O4 crystals in different concentrations. Results review that reduction-induced oxygen vacancy defects distribute shallow or deep near Eu2+ 5d state to obtain the tunable polychromatic long afterglow emission from green to indigo to dark blue. Also, the additional red emission from Eu3+ in the borate glass matrix further enriches the luminescent characteristics by equipping the samples with tunable photoluminescence from yellow-green, yellow to purple. Such material is proved to have good optical information storage ability, which is expected to promote the development of long persistent luminescence materials.