Effect of excitation wavelength (blue vs near UV) and dopant concentrations on afterglow and fast decay of persistent phosphor SrAl2O4:Eu2+,Dy3+*

作者：B. Walfort, Nando Gartmann, Jafar Afshani, A. Rosspeintner, H. Hagemann · 发表于：Journal of Rare Earths · 年份：2021 · DOI：10.1016/J.JRE.2021.07.014 · 被引用次数：32 · 研究领域：Materials Science

Abstract The persistent phosphor SrAl2O4:Eu2+,Dy3+ is the subject of numerous investigations. One often neglected aspect is that in this phosphor, as well as in Sr4Al14O25:Eu2+,Dy3+, there are two different Sr2+ sites which can be occupied by the dopant Eu2+ ions. We first introduce a general scheme of possible energy transfers in these persistent phosphor materials including explicitly both europium ions. This scheme is used as a generic starting point to study experimentally specific pathways. We illustrate this application with the study of the effect of excitation wavelength (444 and 382 nm) on the afterglow of differently doped SrAl2O4:Eu2+,Dy3+ samples, as well as on the emission decay curves. With the same excitation intensity under 444 nm excitation, the resulting afterglow intensity is stronger than under near UV excitation. At 382 nm, Eu2+ ions on both Sr2+ sites in SrAl2O4 are excited, but at room temperature the blue emission is quenched, leading to a loss of photons. The observed effects can further be associated with the ratio of Eu2+ ions and trap states which are modulated by the concentrations of Eu2+ and Dy3+ in SrAl2O4, as well as by temperature. Increasing the nominal Dy3+ content from 0.1 mol% to 0.5 mol% with respect to Sr results in the doubling of the integrated afterglow intensity and confirms thus that Dy3+ ions are indeed involved in the trapping process. The concentration of trap states is much lower than the concentration of Eu2+ ions, as even wit...