Enhanced persistent luminescence of Li2ZnGeO4 host by rare-earth ions (Pr3+, Nd3+ and Gd3+) doping

Abstract

The blue emitting long afterglow phosphor (LAG) Li2ZnGeO4, Li2ZnGeO4:Nd3+, Li2ZnGeO4:Pr3+, and Li2ZnGeO4:Gd3+ were synthesized via traditional high temperature solid-state reaction in air atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscope (PL), luminescence decay, long afterglow spectroscope (LAS) and thermal luminescence spectroscope (TSL) were utilized to characterize and analyze the physical properties of the synthesized phosphors. All phosphor samples present bright blue emission with different intensity under a 254 nm UV lamp. The photoluminescence properties revealed the rare earth ionic (Nd3+, Pr3+ and Gd3+) doping enhanced the luminescence intensity of the host emission and did not change profiles of emission spectra. Further, luminescence decay study showed that the luminescence lifetime of Li2ZnGeO4:R3+ (R = Nd, Pr, Gd) phosphors was increased, indicating energy transform occurred in the processes. After light source was removed, all phosphor sample show evident triple exponential decay behavior. Thermal simulated luminescence study indicated that persistence afterglow of Li2ZnGeO4:Nd3+, Li2ZnGeO4:Pr3+, and Li2ZnGeO4:Gd3+ phosphors were originated from suitable electron or hole traps resulted from rare earth ions (Nd3+, Pr3+ and Gd3+) doping in the Li2ZnGeO4 host.