Energy transfer and red phosphorescence in strontium aluminates co-doped with Cr 3+, Eu 2+ and Dy 3+

Abstract

Cr 3+ activated red long persistent phosphorescence through persistence energy transfer from Eu 2+ to Cr 3+ has been reported in strontium aluminates co-doped with Cr 3+, Eu 2+ and Dy 3+. The decay processes of the red long persistent phosphorescence at 693 nm emission exhibit strong behavior of f–d band of Eu 2+, indicating the occurrence of energy transfer from Eu 2+ to Cr 3+. Lifetime measurements of the blue band show that the energy transfer rates increase with the increase of the Cr 3+ concentration. There are several phases observed in the strontium aluminates. Energy transfer occurs only for the Eu 2+ and Cr 3+ ions that located in the same phase in the host. In SrAl 12O 19 phase, the Eu 2+ ions emit blue light centered at 400 nm and prefer to transferring energy to the Cr 3+ that yields 688 nm emission, while in the Sr 2Al 6O 11 and Sr 4Al 14O 25 phases, the Eu 2+ ions emit at 460 and 490 nm, respectively, and transfer the energy to the Cr 3+ ions that give emission at 693 nm. It is found that the persistent phosphorescence only consists of the 490 and 693 nm bands, indicating the dominant contribution to the phosphorescence is from the ions in the Sr 4Al 14O 25 phase.