Site‐Selective Occupation of Mn2+ Activators for Tunable Luminescence in Well‐Designed CaZnGe2O6 Phosphors

Abstract Crystal‐site engineering is an efficient strategy for tuning the luminescent properties of multicolor inorganic luminescent materials. However, the control of crystallographic site occupancy by a single activator ion in a unitary host lattice to obtain regulable multicolor output remains a formidable challenge. Herein, the strategy to manipulate site‐selective occupation of Mn 2+ activators by exploiting the self‐reduction behavior of Mn ions within the CaZnGe 2 O 6 host matrix is reported to obtain a versatile color output. The choice of manganese precursor (MnO 2 and MnCO 3 ) dictates the local coordination geometry, producing disparate dominant emission: dodecahedral [MnO 8 ] for green luminescence and octahedral [MnO 6 ] crystallographic sites for red emission. Additionally, the introduction of rare‐earth Ln 3+ (Ln = Sm, La, Gd, Tb) co‐dopants modifies the Mn 2+ distribution among available crystallographic sites, facilitating continuous emission color modulation from green to red. The synergistic effect facilitates tunable emission alongside a significantly enhanced photoluminescence quantum yield of 76.58% and prolonged afterglow duration. Practical demonstrations of co‐doped phosphors confirm outstanding performance in anti‐counterfeiting, LED devices, and X‐ray detection applications. This work establishes a novel approach for color regulation in phosphors and provides valuable insights for designing multicolor multifunctional luminescent materials.