Effects of activator site and microstructure on luminescence properties of Eu³⁺-activated LiAlB₂O₅ ceramic phosphor

A comprehensive understanding of the quantity and nature of activator sites is crucial for studying the luminescence performance of phosphors doped with rare earth activators. This research focuses on Eu³⁺-doped LiAlB₂O₅, and Eu³⁺/Si⁴⁺ co-doped LiAlB₂O₅ ceramic phosphors, which were synthesized using a traditional solid-state reaction method. The pure crystalline phase was confirmed by X-ray diffraction (XRD) and Rietveld refinements. The surface characteristics were investigated via scanning electron microscopy (SEM). The luminescence properties such as photoluminescence (PL) spectra, decay curves, CIE color coordinates and quantum efficiency were reported. Site-selective excitation and emission spectra related to the radiative transitions from ⁷F₀ to ⁵D₀ were investigated using a tunable pulsed dye laser (570–590 nm). All samples display a single dominant transition peak at 580.15 nm (17237 cm⁻¹) corresponding to the ⁷F₀ to ⁵D₀ transition, indicating the presence of only one type of Eu³⁺ center within the lattice. The incorporation of Si⁴⁺ alongside Eu³⁺ in LiAlB₂O₅ not only significantly enhances red luminescence efficiency but also improves thermal stability. The inhomogeneous disorder surrounding the Eu³⁺ ions, caused by the excess Si⁴⁺ occupying Al³⁺ sites, results in a notable distortion of the crystal field around the Eu³⁺ centers. This lattice distortion from the substitution of multiple cations effectively increases both the emission efficiency and thermal activation energy of the Eu³⁺-doped phosphors. The cation disorder was analyzed through the excitation and luminescence characteristics in the region of the ⁵D₀ to ⁷F₀ transitions. These findings enhance the potential of using Eu³⁺ as a probe for investigating the microstructure of rare-earth sites in phosphors.