Development of blue excitable persistent phosphor of Ce3+-doped garnet ceramics by bandgap engineering and metal sensitization

Abstract

We investigated the blue excitable persistent luminescence properties in the Ce³⁺-doped garnet ceramics with the composition of Y₃Al_5-xGa_xO₁₂:Ce³⁺ (x=0, 1, 2, 3, 3.5, 4). The persistent luminescence was observed in the sample with x=3 and 3.5 by the blue excitation. In these materials, the energy gap between the lowest 5d₁ excited level of Ce³⁺ and the conduction band is much closer compared with x=0, 1, 2 samples. As a result, the efficient electron transfer to the electron trap occurs through the conduction band by the blue excitation in the x=3 and 3.5 samples. The thermoluminescence (TL) was observed in all the samples by UV excitation and the TL peaks were shifted to lower energy with increasing Ga content. The decreases of the threshold energy of photoionization and the electron trap depth with increasing Ga content can be caused by lowering conduction band. Therefore, we demonstrated that the persistent luminescence properties, such as storagetable wavelength and persistent decay profile, are controlled by changing Ga content. We also discovered that the persistent luminescence intensity and duration time were improved by co-doping with metal ions.