Persistent luminescence in Ba5(PO4)3Cl:Eu2+,R3+ (R = Y, La, Ce, Gd, Tb and Lu)

We investigated the persistent luminescence in europium-doped barium chloroapatite upon codoping with auxiliary rare earth ions. Luminescence properties of the phosphors, including photoluminescence, luminescence decay, and thermoluminescence are systematically studied. We formulated a model of persistent luminescence on the basis of the experimental results. In our model, some Eu2+ ions are oxidized to Eu3+ under short UV excitation, and the released electrons are trapped at the positive defect. The persistent luminescence arises from the recombination of these trapped electrons with the photo-ionized Eu3+ ions. The influence of auxiliary codopants was discussed in terms of ionic potential and ionic radius. Eventually, the concentration quenching of persistent luminescence was reported and discussed.