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

Herein, novel photochromic materials, Sr3YLi(PO4)(3)F:Eu2+,Ln(3+), have been prepared by a conventional high-temperature solid-state reaction. Eu2+ singly doped Sr3YLi(PO4)(3)F showed reversible colorless-magenta photochromism when alternately irradiated by UV and visible light (or thermal treatment). Thus, Sr3YLi(PO4)(3)F: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 Ln(3+) ions. On the basis of thermoluminescence, a schematic of a photochromic mechanism has also been proposed.