Study of a color-tunable long afterglow phosphor Gd1.5Y1.5Ga3Al2O12:Tb3+: luminescence properties and mechanism

Long afterglow phosphors play a significant role in practical applications. However, due to their complex electronic structures, it is difficult to obtain tunable long afterglow phosphors. Herein, a novel long afterglow phosphor, Gd1.5Y1.5Ga3Al2O12:Tb3+, was successfully synthesized. Its detailed structural information was extracted via the Rietveld method, and its corresponding optical properties were further systematically explored via photoluminescence (PL), phosphorescence and thermoluminescence (TL) spectroscopy. Both the photoluminescence and long afterglow properties showed tunable behavior with a variation in the concentration of Tb3+. The investigation of the tunability of its photoluminescence and long afterglow properties revealed that the cross-relaxation energy transfer mechanism contributes to its tunable character. Meanwhile, long-lasting phosphorescence could be observed for a few hours by the naked eye in a dark environment after discontinuing the UV irradiation. Due to the potential existence of the photo-excited (Tb3+)+, the defect clusters were proposed, with oxygen vacancies acting as electron trapping centers and (Tb3+)+ attracting holes. Finally, an appropriate mechanism for the tunable long afterglow emission was proposed.