Improving red afterglow properties of CaZnGe2O6: Mn2+ by co-doping Bi3+

Bi3+, Mn2+ co-doped CaZnGe2O6 red long afterglow materials were prepared by high temperature solid state reaction method. The phosphor has broad excitation band ranging from 220 nm to 350 nm with two peaks at 255 nm and 300 nm and can give blue, green and red emission band peaking at 448 nm, 530 nm and 645 nm, respectively. Due to the emission properties of Bi3+ ions and the Bi3+→Mn2+ energy transfer, the co-doped Bi3+ ions can not only enhance the PL luminescence of the phosphor, but also adjust the emission color. After irradiation of 300 nm ultraviolet light, the phosphors exhibits long-persistent red phosphorescence. Thermoluminescence tests demonstrate that the introduction of Bi3+ ions can increase the trap depth and trap concentration, greatly improving the afterglow time and brightness of the CaZnGe2O6: Mn2+ phosphor. The present work might provide reference for designing new rare earth free red long afterglow materials.