Sr3YLi(PO4)3F:Eu2+,Ln3+: colorless-magenta photochromism and coloration degree regulation through Ln3+ co-doping

Abstract

Herein, novel photochromic materials, Sr₃YLi(PO₄)₃F:Eu²⁺,Ln³⁺, have been prepared by a conventional high-temperature solid-state reaction. Eu²⁺ singly doped Sr₃YLi(PO₄)₃F showed reversible colorless-magenta photochromism when alternately irradiated by UV and visible light (or thermal treatment). Thus, Sr₃YLi(PO₄)₃F:Eu²⁺ might be a potential candidate in various fields such as in imaging, sensors, photo-switches, and erasable optical storage media. The optimal Eu²⁺ doping concentration is experimentally determined to be about 0.5 mol%. The coloring and bleaching processes are attributed to electron trapping accompanied by the generation of F-centers and detrapping by different traps, respectively. Thus, these processes open a window for us to design a simple way to regulate and control the photochromic performance just by adjusting the doping concentration of Eu²⁺ ions or co-doping Ln³⁺ ions. On the basis of thermoluminescence, a schematic of a photochromic mechanism has also been proposed.