Structural and tunable optical properties of LiMgPO4:Tb3+ phosphor fabricated by sol–gel method

Abstract

AbstractIn the study, Tb3+‐doped LiMgPO4 phosphors between .10 and 5 mol% were successfully synthesized by the sol–gel process. The crystal structure of Tb3+‐doped LiMgPO4 was identified by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) analyses. The XRD results for LiMgPO4 ceramics doped with Tb3+ indicated a single‐phase up to 5 mol%, accompanied by lattice shrinkage. An SEM analysis of LiMgPO4 samples showed that increasing Tb3+ concentration reduced grain size but did not cause any significant change in slightly angular and round grains. The emission intensity of phosphor increased from .10 to 5 mol%, and no concentration quenching was observed. The luminescence color of LiMgPO4:Tb3+ phosphor can be tuned from blue to green through cross‐relaxation with the increase in Tb3+ concentration. The photoluminescence emissions of LiMgPO4:Tb3+ on the CIE diagram shifted from blue to green as the Tb3+ concentration increased. The color purity of the 5 mol% Tb3+‐doped phosphor showing the strongest emission was measured at 22.71%, whereas the color‐correlated temperature parameter was found to be 5573 K. The phosphors exhibited bi‐exponential decay profiles, and the observed lifetimes of 5D3 decreased with the increase of Tb3+, where the cross‐relaxation effect increased. The quantum efficiency (ɳQE) of the phosphor was determined using the cross‐relaxation process. For Tb3+ concentrations ranging from .1 to 5 mol%, the ɳQE of the 5D3 state decreased from 62.49% to 28.29%. The research may offer a new perspective and new approaches for tuning luminescence in Tb3+‐doped phosphors.