Well Trap Structures and Bulk-nano Environment Luminescence Centers in CaZnGe_2O_6:Tb~(3+) Long Afterglow Phosphor

摘要

A long afterglow phosphor CaZnGe_2O_6:Tb~(3+) has been prepared by using organic coated luminescence ZnO nanopowder through a high temperature solid-state reaction route. This new CaZnGe_2O~6:Tb~(3+) long afterglow phosphor sample emits the Tb3+ green fluorescence 543 nm emission corresponding to ~5D_4 → ~7F_5 transition under UVA 350 nm illumination. The organic coated luminescence ZnO nanopowder serves to construct shallow well trap for the Tb~(3+) dopant and to minimize electron leakage of well traps. By adjusting the mass ratio of both the bulk ZnO powder (＜1000 nm size) and the organic coated luminescence ZnO nanopowder (5-10 nm size), depth of well traps that dictate luminescence and afterglow properties could be controlled. The optimized long afterglow phosphor sample was found to be made of 70% gm-weight of bulk ZnO powder and 50% gm-weight of organic coated luminescence ZnO nanopowder or CaZn_(0.83)Ge_2O_6:Tb~(3+) phase compound that exhibit afterglow longevity of longer than 3 hours. Therefore, phosphorescence effect is best explained based upon well trap structures model and structure lattice defects play an important role in influencing persistent luminescence phenomena.