Annihilation of the persistent luminescence of MAl2O4 :Eu2+ by Sm3+ co-doping

The calcium aluminates doped with the Eu2+ and Nd3+ ions, CaAl2O4:Eu2+,Nd3+, are a novel and efficient persistent luminescence (i.e. afterglow) material. The Nd3+ ions were found to enhance the persistent luminescence. Some other R3+ co-dopants had similar or opposite, though weaker, effect. The Sm3+ (and Yb3+) ions suppressed almost completely the persistent luminescence and thermoluminescence of the Eu2+ ion. From the UV-excited luminescence and persistent luminescence spectra it was found that the Eu2+ ion acts as a luminescent centre with luminescence at the blue ( lambda(max) = 440 nm) region. The Sm3+ ion was reduced to the divalent state. The thermoluminescence glow curves of the CaAl2O4:Eu2+,Sm3+ material showed that the high-temperature glow peaks, i.e. deep traps, were suppressed almost completely. The Nd:YAG laser-excited high-resolution photoluminescence of the Sm2+ ion confirmed that the Eu2+ ion occupies only one Ca2+ site. Only weak perturbations were observed in the Sm2+ site due to the changes in the environment of the Sm2+ site. (C) 2004 Elsevier Ltd. All rights reserved.