Roles of Eu2+, Dy3+ Ions in Persistent Luminescence of Strontium Aluminates Phosphors

The polycrystalline Eu2 and Dy3 co-doped strontium aluminates SrAl2O4: Eu2 ,Dy3 with different compositions were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence were studied and compared. Results show that the doped Eu2 ion in SrAl2O4: Eu2 , Dy3 phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy3 ion can hardly yield any luminescence under UV-excitation, but effectively enhance the persistent luminescence and thermo-luminescence of SrAl2O4: Eu2 . Dy3 co-doping can help form electron traps with appropriate depth due to its suitable electro-negativity, and increase the density and depth of electron traps. Based on above observations, a persistent luminescence mechanism, electron transfer model, is proposed and illustrated.