Blue-Light Activated Eu²⁺-Doped Green Ultra-Stable Persistent Luminescence Material for Emergency Lighting

Persistent luminescence materials are photoluminescent substances and are extensively utilized in safety and emergency systems, information encryption, anti-counterfeiting, decorative applications, etc. However, most phosphors require excitation in the ultraviolet region of the spectrum, which limits their use in specialized applications. Hence, the development of persistent luminescence phosphors capable of excitation under blue light is of critical importance. Bright green light Ca_8-xMg₃AlGaSi₇O₂₈:x%Eu²⁺ phosphors were synthesized by the high-temperature solid-state reaction method. After Rietveld refinement, the results showed that R_wp = 7.85%, R_p = 5.36%, χ² = 2.12. The space group of the Ca₈Mg₃AlGaSi₇O₂₈ structure is P-421 m. Ca²⁺ is surrounded by 8 O^2- ions, forming a Cs point-symmetric CaO₈ polyhedron. Ca²⁺ and Eu²⁺ share their crystal structure sites and connect eight O^2- to form Ca/EuO₈. Based on the diffuse reflectance spectrum, the optical band energy (Eg) value for CMAGSO:0.1%Eu²⁺ was calculated to be approximately 4.02 eV. The presence of only one broad peak between 35°C and 150°C in the thermoluminescence spectra indicates that there is only one trap in these samples. Through calculation, it can be known that the depth of the trap is between 0.65 and 0.66 eV. The prepared phosphor materials have good application prospects in security and emergency response systems, information encryption, anti-counterfeiting.