Fabrication and luminescence properties of Al2O3-Ce:LuAG composite phosphor ceramics for solid-state laser lighting

Introducing Al2O3 as a secondary phase into Ce:LuAG phosphor ceramics has been realized by solid-state reaction method, but there is much room for improvement on the ingredient uniformity and performance of Al2O3-Ce: LuAG composite phosphor ceramics (CPCs). In this work, the excess of Al3+ in (Ce,Lu)3Al5O12 was regulated to synthesize a series of Al2O3-Ce:LuAG multiphase powders by the co-precipitation method, and homogeneous Al2O3-Ce:LuAG CPCs (the uniform volume fraction between Al2O3 and Ce:LuAG phases) were obtained by vacuum sintering (1775 degrees C x 10 h). With an increase in the Al3+ content, the morphology of the multiphase powders changes from small irregular shapes to porous flocs and flakes interwoven, and Lu3Al5O12 phases tend to convert to LuAlO3 phases. When the Al2O3 content is 78-89 mol% in the CPCs, the average grain sizes of Al2O3 are close to those of Ce:LuAG. Among all CPCs with an Al2O3 content of 68-95 mol%, the 85 mol% Al2O3-Ce: LuAG CPCs initially perform the best in terms of both excitation and emission intensity at room temperature, and their photoluminescence intensities only decrease 4.3% from 25 to 225 degrees C. A solid-state laser lighting device was constructed by using a 450 nm laser source and Al2O3-Ce:LuAG CPCs in a reflection mode. The CPCs with 85 mol % Al2O3 content based on 0.9 W laser diodes (LDs) show the optimum luminous flux (LF) and luminous efficiency (LE) of 244 lm and 266 lm center dot W-1, respectively. Additionally, the LF of all CPCs based on LDs continues to increase without showing luminescence saturation when the power density increases from 1 to 20 W mm-2. When the 85 mol% Al2O3-containing CPCs are excited by a 20 W mm-2 LD, the maximum LF reaches 3624 lm, and the LE decreases only by 12.4% (compared to the data under 1 W mm-2 excitation). Al2O3-Ce:LuAG CPCs have excellent luminescence properties and improved thermal stability, which are promising for the application in solid-state laser lighting.