Improvement of Luminescence Characteristics of ZnGa2O4: Tb3+ Nanophosphors by Ce3+ Codoping

A series of ZnGa2O4:Tb3+,Ce3+ persistent luminescence nanophosphors were prepared by high temperature solid-state reaction. The X-ray diffraction (XRD) patterns of the representative samples are consistent with that of the ZnGa2O4 standard card. Scanning electron microscope (SEM) images show that the particle size of phosphor is enlarged when the Tb3+ ion is doped, however, it becomes smaller again after the Ce3+ ion is codoped. For ZnGa2O4:Tb3+ nanophosphors, there exist intense 492 and 551 nm blue/green emissions under 280 nm excitation, and the optimum Tb3+ doping concentration is 1.7 mol% and the long afterglow time is about 140 min. The PL and long afterglow characteristics of ZnGa2O4:1.7Tb(3+) nanophosphor are significantly improved once the Ce3+ ion is codoped. The PL intensity of ZnGa2O4:1.7Tb(3+) nanophosphor is enhanced by 1.5 times and the long afterglow time is extended to 210 min when Ce3+ doping concentrations are 0.3 and 0.5 mol%, respectively. The internal mechanism of the long afterglow effect of ZnGa2O4:1.7Tb(3+),0.5Ce(3+) nanophosphor is discussed in detail with the help of measurement results of thermoluminescence spectra.