Transition Metal Doped CaGa ₄ O ₇ for Temperature Dependent Dynamic Multicolor Luminescence With Long‐Term and Short‐Term Recoverable Memory

ABSTRACT Dynamic multicolor luminescent materials are highly promising for advanced anti‐counterfeiting and information encryption, yet conventional systems largely rely on lanthanide rare‐earth ions with fixed emission wavelengths and high costs. Here, we report a lanthanide‐free strategy by doping transition‐metal ions Sc 3+ and Cr 3+ into the CaGa 4 O 7 host. The dopant ions synergistically interact with the host lattice, creating multiple trap‐regulated emission channels and simultaneously introducing multilevel trap states, which enable time‐dependent carrier capture and release as the basis for dynamic multicolor luminescence. Under 254 nm UV excitation, CaGa 4 O 7 :Sc exhibits yellow‐to‐blue evolution, while CaGa 4 O 7 :Cr shows red‐to‐blue transitions. Importantly, the dynamic multicolor luminescence is also tunable at higher temperatures, where carriers from shallow traps are depleted, and the blue emission is thermally quenched. Thermoluminescence and optical studies reveal that Sc is associated with deep traps in the host and long‐term memory of dynamic luminescence, whereas Cr is associated with shallow traps and short‐term memory. Leveraging these features, we demonstrate advanced anti‐counterfeiting and information encryption schemes, including time‐gated patterns and ASCII‐coded matrices. This work establishes transition‐metal doping as a general, low‐cost approach to high‐performance dynamic multicolor luminescent materials, highlighting its potential to provide multifunctional, time‐ and temperature‐resolved optical responses for secure information technologies.