The phase transition of color-tunable long afterglow phosphors Sr1.94−xBaxMgSi2O7: Eu2+0.01, Dy3+0.05

The Sr1.94−xBaxMgSi2O7: Eu2+0.01, Dy3+0.05 (x = 0, 0.388, 0.776, 1.164, 1.358, 1.552, 1.649, 1.746, 1.843, 1.94) long afterglow phosphors were successfully prepared under a reducing atmosphere by solid-state reaction method. The changes of crystal structure and luminescence by adjusting the Ba/Sr ratio in the Sr1.94−xBaxMgSi2O7: Eu2+0.01, Dy3+0.05 phosphors have been studied. Tetragonal phase is dominant when x ≤ 1.649. Monoclinic phase emerges at x = 1.164, indicating the original coexistence of tetragonal structure and monoclinic structure. After that, the monoclinic phase becomes more and more obvious with increasing concentration of Ba2+. When the Ba2+ content is equivalent to 90% (x = 1.746), phase transition occurs. At the meantime, the emission and persistent luminescence spectra are changed with the variation of crystal structure, resulting in the changing colors from purplish blue to bluish green. Moreover, the duration of afterglow becomes shorter and the luminescence intensity gets weaker with the increase of Ba/Sr ratio, which is probably due to the change of traps. This significant trending is promising to motivate applications such as color-tunable long afterglow phosphors Sr1.94−xBaxMgSi2O7: Eu2+0.01, Dy3+0.05.