Enhanced Green and Orange–Red Dual Luminescence Emissions of Zn _0.5 Ca _0.5 Al ₂ O ₄ : Tb ³⁺ , Sm ³⁺ Phosphors Stimulated by Crystallinity: Effects of Annealing Temperature

This study investigates the effects of varying annealing temperatures (AT) on the structural and luminescent properties of codoped Zn 0.5 Ca 0.5 Al 2 O 4 :0.1% Tb 3+ , 0.1% Sm 3+ (ZC:0.1% Tb 3+ 0.1% Sm 3+ ), synthesized via the citrate sol–gel method. The AT significantly impacts the crystallinity, phase composition, and photoluminescent behavior of the codoped phosphor. Optimal luminescence efficiency and color purity are observed at an AT of 900°C, which provides high luminescence efficiency and desirable color characteristics. At lower temperatures, the emission is more bluish‐green, shifting toward yellow–red with increased AT. However, beyond 900°C, thermal quenching effects reduce emission intensity and alter chromaticity coordinates, leading to decreased color purity. This research highlights the importance of precise temperature control in developing high‐performance phosphors for advanced optoelectronic applications.