Long-Lasting Afterglow Characteristics of Eu, Dy Codoped SrO-Al₂O₃ Phosphor

Abstract

By codoping Dy³⁺ into the SrAl₂O₄:Eu²⁺ phosphor, long persistent phosphorescence was observed and its afterglow characteristics were investigated. The excitation wavelength suitable for long persistent phosphorescence was 200-250nm, much shorter than the wavelength of 4f⁷-4f⁶5d absorption of the Eu²⁺ ions, suggesting that the energy levels of electron traps are higher than the 4f⁶5d level. The phosphorescence intensity and its lifetime increased with increasing temperature. The depth of the electron traps was calculated from the Hoogenstraaten's plot of glow curves at about 0.3 and 0.6eV. From the temperature dependence of decay curves, the deeper trap is considered to contribute to the long-lasting afterglow.