Structural and tunable optical properties of LiMgPO ₄ :Tb ³⁺ phosphor fabricated by sol–gel method

Abstract In the study, Tb ³⁺ ‐doped LiMgPO ₄ phosphors between .10 and 5 mol% were successfully synthesized by the sol–gel process. The crystal structure of Tb ³⁺ ‐doped LiMgPO ₄ was identified by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) analyses. The XRD results for LiMgPO ₄ ceramics doped with Tb ³⁺ indicated a single‐phase up to 5 mol%, accompanied by lattice shrinkage. An SEM analysis of LiMgPO ₄ samples showed that increasing Tb ³⁺ 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 LiMgPO ₄ :Tb ³⁺ phosphor can be tuned from blue to green through cross‐relaxation with the increase in Tb ³⁺ concentration. The photoluminescence emissions of LiMgPO ₄ :Tb ³⁺ on the CIE diagram shifted from blue to green as the Tb ³⁺ concentration increased. The color purity of the 5 mol% Tb ³⁺ ‐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 ⁵ D ₃ decreased with the increase of Tb ³⁺ , where the cross‐relaxation effect increased. The quantum efficiency ( ɳ _QE ) of the phosphor was determined using the cross‐relaxation process. For Tb ³⁺ concentrations ranging from .1 to 5 mol%, the ɳ _QE of the ⁵ D ₃ state decreased from 62.49% to 28.29%. The research may offer a new perspective and new approaches for tuning luminescence in Tb ³⁺ ‐doped phosphors.