Luminescent ceramics LuGdAG:Ce with high color rendering index: effect of thermal annealing on luminescent properties

The optical properties of LuGdAG:Ce ceramics with gadolinium content ranging from 0 to 100 atomic percent were investigated. The study demonstrated that as the gadolinium content increases, the light transmittance of the ceramics also rises, while the luminescence spectrum shifts toward the red region. Additionally, the color temperature decreases, luminescence efficiency declines, but the color rendering index $(R_a)$ improves. Following annealing in air, a significant enhancement in luminescence was observed in ceramics with high gadolinium content, although this was accompanied by a reduction in $R_a$. These findings indicate that LuGdAG:Ce ceramics hold promise for use in warm white light sources with a high color rendering index.