Preparation and characterization of an Hf-doped zinc silicate long-lasting phosphorescent material

Hf⁴⁺-doped Zn₂SiO₄ phosphor emitting long-lasting cyan light was prepared by the conventional high temperature solid-state technique. The emission spectrum of the Hf⁴⁺-doped phosphor exhibits one broad band peaking at 471 nm in the visible region excited by 254 nm. The cyan-light afterglow can last about 40 min in darkness after being irradiated with 254 nm UV lamp for 10 min (250 mW/cm²). The afterglow decay curve can be fitted into a second-order exponential curve. The thermoluminescence (TL) curve shows two glow bands centered at about 386 K (0.61 eV) and 440 K (1.56 eV), respectively, with the lower trap energy level being responsible for the long-lasting afterglow emission. A possible mechanism of the long-lasting phosphorescence based on the experimental results is proposed.