X-ray-activated long afterglow in Tb-doped CaZnOS-layered semiconductors

Abstract

Long afterglow materials feature long-lasting luminescence after the cessation of the excitation source. The rising demand for afterglow materials in many applications such as deep tissue imaging, ultrasensitive sensing, and radiation detection has led to extensive research on X-ray-activated afterglow systems. However, the progress in this field is constrained by the limitation and shortage of radiation-induced afterglow materials. Herein, a newly X-ray-excited long afterglow phosphor CaZnOS:Tb3+ has been developed by using lithium-assisted synthetic protocol. Afterglow properties of Tb3+-doped CaZnOS microcrystals are systematically investigated by considering the dopant concentration, reaction temperature, reaction time, reaction atmosphere, and gas flow. As the gas flow of argon atmosphere increases from 0.05 to 0.5 L/min, the CaZnOS:Tb3+ microcrystals exhibit a distinct change in trap depth from 0.59 to 0.75 eV, corresponding to a gradual increase in afterglow time. Together with thermoluminescence analysis, the long afterglow mechanism is also discussed in this work. These results highlight the importance of reaction gas flow for the efficient regulation of traps and defects in afterglow materials. Furthermore, they provide a fundamental design principle and new route for the creation of lanthanide-doped CaZnOS afterglow phosphors.