Effect of excitation wavelength(blue vs near UV)and dopant concentrations on afterglow and fast decay of persistent phosphor SrAl_(2)O_(4):Eu^(2+),Dy^(3+)  

作　　者：Bernhard Walfort Nando Gartmann Jafar Afshani Arnulf Rosspeintner Hans Hagemann 

机构地区：[1]LumiNova AG,Switzerland,Speicherstrasse 60a,CH-9053,Teufen,Switzerland [2]Dépt.de Chimie Physique,Universitéde Genève,30,Quai E.Ansermet,CH 1211,Geneva 4,Switzerland

出　　处：《Journal of Rare Earths》2022年第7期1022-1028,共7页稀土学报（英文版）

基　　金：Project supported by the Swiss National Science Foundation(200020_182494,200021_169033);Innosuisse(25902.1 PFNM-NM,15217.1PFIW-IW)。

摘　　要：The persistent phosphor SrAl_(2)O_(4):Eu^(2+),Dy^(3+)is the subject of numerous investigations.One often neglected aspect is that in this phosphor,as well as in Sr_(4)Al_(14)O_(25):Eu^(2+),Dy^(3+),there are two different Sr^(2)+sites which can be occupied by the dopant Eu^(2+)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 SrAl_(2)O_(4):Eu^(2+),Dy^(3+)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,Eu^(2+)ions on both Sr^(2)+s ites in SrAl_(2)O_(4)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 Eu^(2+)ions and trap states which are modulated by the concentrations of Eu^(2+)and Dy^(3+)in SrAl_(2)O_(4),as well as by temperature,Increasing the nominal Dy^(3+)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 Dy^(3+)ions are indeed involved in the trapping process,The concentration of trap states is much lower than the concentration of Eu^(2+)ions,as even with low excitation densities,a plateau of integrated afterglow intensity(corresponding to the total number of accessible traps)is reached.We postulate that an important fraction of excited Eu^(2+)ions can potentially transfer their energy to trap states.Once that all traps are filled or in a dynamical filling-depletion process under illumination(with thermal and/or optical depletion processes),for the remaining Eu^(2+)a"normal"steady-state emission is observed.The luminescence decay curves at 520 nm measure

关 键 词：Persistent phosphor Strontium aluminate EUROPIUM Forster energy transfer Rare earths 

分 类 号：TQ422[化学工程]