Greatly enhanced Dy3+ emission via efficient energy transfer in gadolinium aluminate garnet (Gd3Al5O12) stabilized with Lu3+
Dy3+-doped and Lu3+-stabilized gadolinium aluminate garnet solid solutions of [(Gd1−xLux)1−yDyy]3Al5O12 (x = 0.1–1.0, y = 0–0.10) have been developed as efficient phosphors for simultaneously strong blue (∼483 nm, the 4F9/2 → 6H15/2 transition of Dy3+) and yellow (∼584 nm, the 4F9/2 → 6H13/2 transition of Dy3+) emissions. The efficient energy transfer from Gd3+ to Dy3+ produces an additional excitation band, being the strongest, at ∼275 nm that corresponds to the 8S7/2 → 6IJ intra-f–f transition of Gd3+. With the energy transfer, significantly stronger Dy3+ emission (roughly two-fold) was obtained through excitation of Gd3+ at 275 nm rather than direct excitation of Dy3+ at 352 nm (6H15/2 → 4I11/2 + 4M15/2 + 6P7/2 transition, the strongest intra-f–f transition of Dy3+). The quenching concentration of Dy3+ was determined to be ∼2.5 at%, and the quenching mechanism was suggested to be dipole–dipole interactions. At the optimal Dy3+ content of 2.5 at%, increasing Lu3+ substitution tends to weaken both the excitation and emission bands owing to the higher electronegativity of Lu3+. Comparative studies showed that the best luminescent [(Gd0.8Lu0.2)0.975Dy0.025]AG phosphor has an integrated emission intensity roughly 2.5 and 4 times those of its (Y0.975Dy0.025)AG and (Lu0.975Dy0.025)AG counterparts, respectively. The effects of processing temperature and Lu3+/Dy3+ contents on phase evolution, crystal structure, particle morphology, PLE/PL properties, and fluorescence lifetime of the phosphor are thoroughly investigated. Owing to its enhanced emission and high theoretical density, the (Gd,Lu)AG:Dy3+ phosphor developed in this work may potentially be used as a new type of photoluminescent and scintillation material.