Study on luminescence properties of Eu2+ doped K-β-Al2O3 blue phosphor and its anti-counterfeiting application

Eu²⁺ doped K-β-Al₂O₃ blue phosphors were synthesized via the high temperature solid-state method. The crystal structure, microstructure and photoluminescence properties of the samples were characterized using XRD, SEM and fluorescence spectrum analysis. The results indicate that within the Eu²⁺ doping concentration range, the synthesized products maintain a single K-β-Al₂O₃ phase, and the lattice constant gradually decreases as the Eu²⁺ doping concentration increases, suggesting that Eu²⁺ ions occupy the K⁺ sites in the conductive layer of the host crystal structure. The synthesized phosphor exhibits a hexagonal flake morphology, with uniform particle size and excellent dispersion performance. Under 345 nm near ultraviolet light excitation, the photoluminescence spectra display a single-peak narrow-band emission, with the emission peak centered around 445 nm, this emission originates from the 4f - 5d energy level transition of Eu²⁺. as the Eu²⁺ doping concentration increases, the luminescence intensity of phosphors increases first rises and then declines. The maximum luminescence intensity is achieved when the Eu²⁺ doping concentration reaches 7 mol%. Moreover, the synthesized phosphors demonstrate excellent thermal stability, retaining 76.5 % of their initial intensity at 423 K. The color coordinates of K_1-xAl₁₁O₁₇: xEu²⁺ phosphors are situated at the boundary of the blue light region under 345 nm near-ultraviolet light excitation, with a color purity exceeding 98 %, approaching pure blue. An anti-counterfeiting ink formulated with KAO: 0.07Eu²⁺ blue phosphor and epoxy resin glue can achieve ideal anti-counterfeiting effect after when applied to patterns.