Synthesis and photoluminescence properties of RE³⁺ (RE = Eu, Dy, and Sm)-doped BaAl₂Ge₂O₈ phosphors

Trivalent rare-earth (RE³⁺; RE = Eu, Dy, and Sm) ions doped BaAl₂Ge₂O₈ (BAGO) phosphors were synthesized using a pechni-type sol-gel method. The phase formation of the BAGO host lattices prepared at various temperatures was characterized by X-ray diffraction, which revealed a monoclinic crystal structure with space group I12/c (No. 15). The morphological characteristics of the optimized BAGO:RE³⁺ phosphors, characterized by using a field-emission scanning electron microscope, showed that they had aggregated structures of micrometer-sized particles. The photoluminescence (PL) properties of BAGO:RE³⁺ phosphors under ultraviolet (UV) and near-UV excitations showed strong and characteristic emissions. The concentration quenching behaviors were systematically investigated to determine the optimal doping concentration of each phosphor. Additionally, temperature-dependent PL measurements were performed to evaluate the thermal stability of the phosphors, and Commission Internationale de l'Éclairage chromaticity coordinates for the optimized phosphors were calculated to assess their suitability for solid-state lighting applications.