Persistent luminescence of Eu2+ doped alkaline earth aluminates, MAl2O4:Eu2+

The polycrystalline Eu2+ and RE3+ (rare earth) doped alkaline earth aluminates MAl2O4:Eu2+,RE3+ (M=Ca and Sr) were prepared by a solid state reaction starting from the corresponding oxides (Al, RE) and carbonates (Ca, Sr). The UV-excited photoluminescence, persistent luminescence (afterglow) and thermoluminescence of these materials was studied and compared, The two spectra (band position and width) were very similar indicating that the luminescent centre is an Eu2+ ion in both cases. A slight blue shift was observed in the afterglow emission in some cases. The RE3+ co-doping had no effect on the position and shape of the persistent luminescence band but the Nd3+ and Dy3+ ions enhanced the most the afterglow and thermoluminescence of the CaAl2O4:Eu2+ and SrAl2O4:Eu2+ materials, respectively. Easily reducible rare earth ions such as Sm3+ and Yb3+ suppressed both the afterglow and thermoluminescence of MAl2O4:Eu2+. Based on these observations, the mechanism of RE3+ co-doping is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.