Tunable visible luminescence from Tb3+/Fe3+ co-doped LiAl5O8 under UV and X-ray excitation

In this work, we report the synthesis and optical characterization of LiAl₅O₈ co-doped with Tb³⁺ and Fe³⁺ ions, aiming to investigate tunable visible luminescence under different excitation conditions. The samples were prepared using the sol-gel method, with glucose as the chelating agent. Photoluminescence (PL) responses were analyzed under ultraviolet excitation at 215 nm and 270 nm, while X-ray-excited optical luminescence (XEOL) was investigated under excitation at the L${}_{III}$-edge of Tb³⁺ (7520 eV). The results show that co-doping enables effective control of the emission color, with green and red contributions from Tb³⁺ and Fe³⁺ ions, respectively, confirming the potential of Fe³⁺ as a red-emitting center in co-doped systems for tunable luminescence applications. The evolution of chromaticity coordinates (x, y) and correlated color temperature ($T_p$) was evaluated using CIE 1931 diagrams. Emission tones ranged from warm white to orange under 215 nm excitation, indicating potential for white light-emitting diode (WLED) applications, and shifted from green to intense red under 7520 eV excitation. These findings demonstrate that all samples exhibit visible luminescence under both near-ultraviolet and X-ray excitation, confirming their potential for application in solid-state lighting devices and scintillator materials.