Gd₃al₅O₁₂ Crystal Structure Stabilization By Lu³⁺ Doping And Photoluminescence Properties Of （Gd,Lu）₃Al₅O₁₂:Eu³⁺ Red Phosphors

The syntheis of precursors for (Gd1-xLux)3Al5O12and [(Gd1-xLux)3-yEuy]Al5O12garnets was achieved via reverse-strike coprecipitation, with rare-earth nitrates as the mother salts and ammonia bicarbonate as the precipitatnt. Oxide powders were then obtained by calcining the precursors at the five selected temperatures of800℃、900℃、1000℃、1150℃and1300℃. Detailed characterizations of the precursors and the oxides were performed by the combined techniques of FT-IR, DTA/TG, SEM, TEM, BET, XRD, and PLE-PL. The results showed that the thus made precursors possess a general composition of (NH4)x(Gd,Lu,Eu)3Al5(CO3)y(OH)·nH2O, and the particles, having diameters of about50nm, are well desipersed. Lu3+doping can effectively stabilize the metastable garnet structure of Gd3Al5O12, and the formation temperature of the intended ganets successively decreases at a higher Lu3+incopopration. Lu3+doping deforms the garnet lattice, and the lattice constant gradually decreases at a higher Lu3+content. The cubic lattice of garnet allows the Eu3+activators to reside at the centrosymmetric sites of D2, and thus the photoluminescence spetra of the garnet-based phosphors exhit strong5D0�'7F1emissions at591nm while weak5D0�'7F2transitions at611nm. The phosphor powders show vivid organge-red colors under the254nm ultraviolet exciations from a hand-held UV lamp. At a fixed Lu3+content, the luminescence intensity of the material improves up to5at%of Eu3+and then decreases, exhibiting a luminescence quenching concentration of5at%. Lu3+doping lowers the covalency of the Ln-O bond in the garnet lattice, owing to the higher electronegativity of Lu3+, and thus tends to lower the luminosity of the phosphor materials.