Silicate-based persistent phosphors

Abstract Eu2+-doped alkaline-earth silicates are the second most studied group of persistent luminescent inorganic phosphors after aluminates, such as SrAl2O4. Silicates are comparable with the aluminates in terms of chemical stability, high quantum efficiency and large band gap, but offer advantages including better water resistance and lower calcination temperature. Their applications range from traditional uses such as traffic signs, tile decoration or fluorescent lamps to more advanced ones such as solar cells, LEDs or in the medical field. The highest persistence has been found in (Ca,Sr,Ba)3MgSi2O8: Eu2+, Dy3+, Ba4(Si3O8)2: Eu2+, Dy3+ or Sr2MgSi2O7: Eu2+, Dy3+. Various synthesis routes have been employed to obtain crystals of these phases, such as sol-gel, hydrothermal and combustion synthesis and, more commonly, solid-state reaction. The preparation of silicate phosphors from glass crystallization has not yet been widely explored. Here, we review the progress made in the research of these inorganic crystalline phosphors, the proposed persistent luminescence mechanisms taking place and the different preparation methods employed to date, with special attention paid to the Sr2MgSi2O7: Eu2+, Dy3+ phase due to its long afterglow emission.