The influence of auxiliary codopants on persistent phosphor Sr2P2O7:Eu2+,R3+ (R = Y, La, Ce, Gd, Tb and Lu)

We investigate the persistent luminescence in europium-doped strontium pyrophosphate upon codoping with auxiliary rare earth ions. The persistent phosphors are synthesized via solid-state reaction method under flowing N2 + H2. Under UV irradiation, broadband emission persistent luminescence located at 420 nm is observed in all of these phosphors at room temperature. The effects of auxiliary rare earth ions on Sr2P2O7:Eu2+ are discussed according to the decay curves and thermoluminescence spectra. Sr2P2O7:Eu2+,Lu3+ shows the best performance, while and La3+ and Ce3+ codoped samples are the weakest. The influence of auxiliary codopants is discussed in terms of ionic potential and ionic radius. We derive an empirical formula based on the experimental results.