White light generation from YAG/YAM:Ce³⁺, Pr³⁺, Cr³⁺ nanophosphors mixed with a blue dye under 340 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. - Highlights: • YAG/YAM:Ce³⁺, Pr³⁺, Cr³⁺ nanophosphors were synthesized with a hydrothermal method. • Ammonia introduced during the synthesis increased the emission of nanophosphors. • White light was obtained by combining the emissions of a blue dye and nanophosphors. • The CIE coordinates for this white light are (0.30, 0.36)