X-ray absorption study of rare earth ions in Sr2MgSi2O7:Eu2+,R3+ persistent luminescence materials

Luminescence and x-ray absorption measurements of persistent SrAl2O4:Eu,Dy powders: Evidence for valence state changes

“…Most authors agree on the general idea that charge carriers are created inside the material, which subsequently get trapped by long-lived energy levels inside the forbidden zone of the host crystal. However, the nature of these traps and the type and origin of the trapped carriers remains the subject of debate, although several structural and optical analytical techniques (such as x-ray absorption spectroscopy 5,6 , electron spin resonance 7 , photoconductivity measurements 8 and thermoluminescence spectroscopy 9 ) have been applied to a wide range of persistent phosphors. Often, rare earth codopants considerably enhance the afterglow, but also several non-codoped persistent phosphors have been reported 2,10 .…”

Electronic structure of defects in Sr2MgSi2O7:Eu2+,La3+ persistent luminescence material

“…The Eu 2+ ion becomes either a Eu 3+ species or (more likely) a Eu 2+ −h + pair. The EXAFS results published earlier [45] have not given a clear solution to this detail yet. The decharging process involves the temperature controlled gradual release of the trapped electrons followed by the migration of electrons to the Eu 2+ −h + (or Eu 3+ ) center through the conduction band for the recombination.…”

Luminescent ecstasy tablets. Authentication tool or cunning marketing tactic?

“…Eu 2+ ion acts as the luminescence center, and it is known that some rare earth (R 3+ ) co-dopants enhance the persistent luminescence obtained with Eu 2+ doping alone. The exact role of the co-dopants and that of other lattice defects is uncertain, but the R 3+ ions have been suggested to trap holes or electrons or just to create/modify defects due to charge compensation [6,7] . Essentially the dopant absorbs the radiated light and transfers this energy to the phosphor (SrAlO 4 ) which re-emits, in this case, green light.…”