Extending the afterglow in CaAl_2O_4:Eu,Nd persistent phosphors by electron beam annealing

White, well-crystallized and strongly persistent luminescent CaAl 2 O 4 :Eu 2+ ,Nd 3+ powders were obtained by electron-beam annealing.The electron-beam annealing resulted in a full reduction of Eu 3+ to Eu 2+ , based on the luminescence spectra.Considerable grain growth was observed and the annealed powder crystallized in the monoclinic phase of calcium aluminate.The afterglow intensity was about three times this of commercially available powder and the afterglow duration extended to 10 hours, considering the 0.32mcd/m 2 photopic threshold level.