Mn2+ activated green, yellow, and red long persistent phosphors

Mn2+ activated long persistent phosphors, CaAl2O4:Mn2+, Ce3+, Ca2Al2SiO7:Mn2+, Ce3+ and MgSiO3:Mn2+ Eu2+, Dy3+, were prepared. Long persistent phosphorescence in green, yellow, and red have been observed in the systems with persistence time over 10 h for the green (525 nm) and the yellow (550 nm) and 4 h for the red (660 nm). Emission and excitation spectra showed that Mn2+ emission was dominant in these materials. Long persistent phosphorescence was also measured in the systems without Mn2+ as a co-dopant. The emissions were much stronger due to 5d-4f transitions in Ce3+ and Eu2+ other than 3d-3d transitions in Mn2+. The disappearances of the long persistent afterglow in these systems when co-doped with Mn2+ suggested the existence of a. strong, persistent energy transfer from Ce3+ and Eu2+ to Mn2+. (C) 2002 Elsevier Science B.V. All rights reserved.