Phosphorescent and thermoluminescent properties of SrAl ₂O ₄:Eu ²⁺, Dy ³⁺ phosphors prepared by solid state reaction method

Long persistent SrAl ₂O ₄:Eu ²⁺ phosphors co-doped with Dy ³⁺ were prepared by the solid state reaction method. The main diffraction peaks of the monoclinic structure of SrAl ₂O ₄ were observed in all the samples. The broad band emission spectra at 497 nm for SrAl ₂O ₄:Eu ²⁺, Dy ³⁺ were observed and the emission is attributed to the 4f ⁶5d ¹ to 4f ⁷ transition of Eu ²⁺ ions. The samples annealed at 11001200°C showed similar broad TL glow curves centered at 120°C. The similar TL glow curves suggest that the traps responsible for them are similar. The long afterglow displayed by the phosphors annealed at different temperatures, may be attributed to the Dy ³⁺ ions acting as the hole trap levels, which play an important role in prolonging the duration of luminescence.