White light generation from YAG/YAM:Ce3+, Pr3+, Cr3+ nanophosphors mixed with a blue dye under 340Â nm excitation

The structural and luminescent properties of Y3Al5O12/Y4Al2O9:Ce3+(0.1%)-Pr3+(0.1%) -Cr3+ (trace impurities) nanophosphors synthesized by a simple hydrothermal method were studied. The crystalline phase was composed of Yttrium Aluminum Garnet (YAG) and Yttrium Aluminum Monoclinic (YAM) depending on the ammonia concentration and annealing temperature. Ammonia increased the stabilization of YAG from 55 wt% to 63 wt% in the samples annealed at 900 °C, and an increment of 83% of the overall emission under 460 nm excitation was observed. Quenching of the emitted signal after annealing at 1100 °C was observed in spite of single YAG crystalline phase stabilization, due to the formation of Ce4+, Pr4+, and color centers. In addition to the green-yellow emission from Ce3+, all samples present a broad red emission band produced by the relaxations from the broad band 4T2 toward the 4A2 energy level of Cr3+ impurities, under 340 nm excitation. By taking advantage of this broad green-yellow-red emission and using a blue dye, white light with CIE coordinates of (0.30, 0.36) under 340 nm excitation was produced.