Synthesis and luminescence properties of Tb3+:NaGd(WO4)2 novel green phosphors

Tb3+:NaGd(WO4)2 (Tb:NGW) phosphors with different Tb3+ concentrations have been synthesized by a mild hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation and emission spectra and decay curve were used to characterize the Tb:NGW phosphors. XRD analysis confirmed the formation of NGW with scheelite structure. SEM study showed that the obtained Tb:NGW phosphors appeared to be nearly spherical and their sizes ranged from 1 to 1.5 μm. The excitation spectra of these systems showed an intense broad band with maximum at 270 nm related to the O→W ligand-to-metal charge-transfer state. Photoluminescence spectra indicated the phosphors emitted strong green light centered at 545 nm under UV light excitation. Analysis of the photoluminescence spectra with different Tb3+ concentrations revealed that the optimum dopant concentration for Tb3+ is about 15 at% of Tb3+ ions in Tb:NGW phosphors.