Orange persistent luminescence of LuBaZn3GaO7: Bi3+ phosphor based on defect induction for optical thermometer and multi-mode anti-counterfeiting

In this study, the Bi3+ doped LuBaZn3GaO7 fluorescent powder was produced using a high-temperature solid-state technique, and its long afterglow luminescence and dynamic anti-counterfeiting capabilities were thoroughly examined. Under the ultraviolet (UV) light excitation, the LuBaZn3GaO7 host exhibits broadband self-activated emission band peak at 594 nm, attributed to the O-vacancies. Upon Bi3+ doping, the phosphor produces a narrow emission band in the 350–450 nm wavelength range, which is caused by the 3P1–1S0 transition of the Bi3+ ions in the Ba2+ site. Remarkably, oxygen vacancy-induced electronic localization around the Bi3+ ions increases the emission intensity of LuBaZn3GaO7:0.01Bi3+ around ten times that of LuBaZn3GaO7 between 450 and 850 nm wavelength. With the variation in excitation light wavelength, the intensity of the two emission bands of LuBaZn3GaO7: Bi3+ changed accordingly, exhibiting multi-color luminescence. While the excitation was removed after 3-min irradiation, LuBaZn3GaO7: Bi3+ phosphors continued to emit for 10 min. Moreover, the phosphor emission has good temperature-sensitive characteristics based on the fluorescence intensity ratio (FIR) of the emission bands of Bi3+ ions and host. Hence, an optical thermometry with high-temperature sensitivity was constructed. Consequently, it can be concluded that fluorescent powder has the potential to be applied in the fields of fluorescence temperature measurement and anti-counterfeiting.