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High-brightness laser lighting requires high luminous efficacy and high thermal performance of luminescent materials. In this study, we designed and fabricated single-phase YAG:Ce ceramics with differential grain sizes by combining the coarse commercial phosphor and fine powder of precusor. The large YAG:Ce grains mainly contribute to excellent luminescence properties. The small YAG:Ce grains not only change the direction of light propagation to improve the luminous efficiency but also effectively increase the Ce3+ content to improve the absorption of blue light, which significantly further enhance the luminescence properties compared with the second phase in the YAG:Ce-base composite ceramics. The luminescent ceramic with 40 wt% large grains sintered under 1550 °C has the highest luminous efficacy of 398.5 lm/W. Compared with the Al 2 O 3 –YAG:Ce composite ceramic, the single-phase YAG:Ce ceramic effectively increased the absorption of blue light to enhance the luminescence properties without the adverse effects caused by the transverse scattering of light in the Al 2 O 3 phase. After encapsulating the ceramic onto a radiator, a high luminous flux of 7697.6 lm under the blue-laser excitation of 3.0 A (54.6 W) was obtained. These indicated its broad application prospects in high-power solid-state laser lighting. [ABSTRACT FROM AUTHOR]

The metastable garnet lattice of Yb/Er co-doped Gd 3 Al 5 O 12 (GdAG:Yb/Er) has been effectively stabilized by doping with significantly smaller Lu 3+ to form (Gd,Lu)AG:Yb/Er solid solutions. The phase-pure (Gd,Lu)AG:Yb/Er garnet particles have been successfully achieved by calcining their respective precursors synthesized via carbonate co-precipitation. Partially replacing Gd 3+ with Lu 3+ up to 50 at% ( x =0.5) not only lowers the temperature of garnet crystallization, but also raises the theoretical density of the material. The resultant [(Gd 1− x Lu x ) 0.948 Yb 0.05 Er 0.002 ]AG ( x =0.1–0.5) powders, with good dispersion and fairly uniform particle morphology, exhibit strong green (~510 to 590 nm, 2 H 11/2 , 4 S 3/2 → 4 I 15/2 transitions of Er 3+ ) and red (~635 to 700 nm, 4 F 9/2 → 4 I 15/2 transition of Er 3+ ) emissions under 978 nm laser excitation. The Lu 3+ incorporation effect on the visible emission color and intensity of Er 3+ , as well as the dependence of emission intensity on pumping power were all discussed in detail. The up-conversion phosphor of Yb/Er codoped (Gd,Lu)AG garnet developed in this work may potentially be used as a new type of luminescent material. [ABSTRACT FROM AUTHOR]