Development of Tb3+ activated gadolinium aluminate garnet (Gd3Al5O12) as highly efficient green-emitting phosphors

The powder processing of (Gd1-xTbx)3Al5O12 (GdAG:Tb3+) solid solutions was achieved through precursor synthesized via carbonate precipitation, followed by calcination at 1500 °C. The performance of the GdAG:Tb3+ phosphors were characterized by the combined techniques of XRD, FE-SEM, HR-TEM, PLE/PL, and fluorescence decay analyses. Lower Tb3+ doping can stabilize the crystal structure of GdAG garnet against its thermal decomposition. The GdAG:Tb3+ phosphors with good dispersion and fairly uniform particle morphology exhibit a series of 5D4-7FJ transitions of Tb3+ with strongest green emission at ~544 nm (5D4-7F5 transitions of Tb3+) under UV excitation at ~277 nm (4f8−4f75d1 transition of Tb3+). The later is overlapping with 8S7/2-6IJ intra f-f transition of Gd3+ indirectly suggesting the existence of energy transfer from Gd3+ to Tb3+. With the Gd3+-Tb3+ energy transfer, higher Tb3+ emission and quantum efficiency than the well-known YAG:Tb3+ and LuAG:Tb3+ were obtained in the present work. The effects of Tb3+ content on luminescent property of the phosphor, especially PLE/PL properties, fluorescence lifetime and quantum efficient, were thoroughly investigated, which were also compared to those of Tb3+-activated YAG and LuAG compounds. The CIE chromaticity coordinates and quenching concentration of GdAG:Tb3+ were determined to be (~0.37, ~0.56) and ~10 at%, respectively. Keeping the optimum Tb3+ content at ~10 at%, the (Gd0.9Tb0.1)AG phosphor possesses high internal and external quantum efficiencies of ~88.7% and ~73.6% under ~277 nm excitation, respectively. Owing to its improved luminescent property and high theoretical density, the phosphors of (Gd1-xTbx)AG garnet developed in the present work are expected to be used as a new type of photoluminescent material.