Persistent Luminescence of Eu^2☎ and Na^☎ Doped Alkaline Earth Aluminates

Abstract

The luminescence and afterglow properties of the Eu^2☎ and Na^☎ doped alkaline earth aluminales, stoichiometric and non-stoichiometric (M_x Al₂O₄:Eu^2☎, Na^☎; M = Ca or Sr, x = 0.97, 1.00 or 1.03, X_Na, = 0.02), were studied. Broad band luminescence and afterglow of the Eu^2☎ ion were observed in the blue (λ_max = 440nm) and green (λ_max = 520nm) region for the calcium and strontium aluminates, respectively. Both Na^☎ co-doping and strontium excess quenched the afterglow efficiently. The results supported the mechanism of the persistent luminescence where the cation vacancies act as traps. The results for the calcium aluminates were ambiguous, probably due to the slightly larger ionic radius of the Na^☎ with respect to that of Ca^2☎. The sodium ions may not fit into the calcium sites and thus form (an) independent compound(s).

Keywords:

• Persistent luminescence
• Alkaline earth aluminate
• Non-stoichiometry
• Sodium co-doping