A novel rare-earth free red long-persistent phosphor: Mg2GeO4:Mn4+

Red-emitting long-persistent phosphor Mg2GeO4: Mn4+ was prepared by a high-temperature solid-state reaction. The photoluminescence and afterglow properties of Mg2GeO4: xMn4+ phosphors were studied systematically. Furthermore, to improve the afterglow performance, co-doped Re3+ (Re = Pr, Er, Nd and Yb) ions into Mg2GeO4: 0.001Mn4+ separately to adjust the trap depth or increase the trap density was performed. The duration of Mg2GeO4: 0.001Mn4+ can be observed 30 min by naked eyes, and the initial brightness and afterglow duration are significantly improved after Re3+ ions are doped respectively. Especially, the afterglow emission of Mg2GeO4: Mn4+, Yb3+ can last for 2 h. This investigation shows up a rare Mn4+-doped long-afterglow phenomenon, and provides a new and efficient red afterglow material for potential application.