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

Introducing Al 2 O 3 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 Al 2 O 3 -Ce:LuAG composite phosphor ceramics (CPCs). In this work, the excess of Al 3+ in (Ce,Lu) 3 Al 5 O 12 was regulated to synthesize a series of Al 2 O 3 -Ce:LuAG multiphase powders by the co-precipitation method, and homogeneous Al 2 O 3 -Ce:LuAG CPCs (the uniform volume fraction between Al 2 O 3 and Ce:LuAG phases) were obtained by vacuum sintering (1775 °C × 10 h). With an increase in the Al 3+ content, the morphology of the multiphase powders changes from small irregular shapes to porous flocs and flakes interwoven, and Lu 3 Al 5 O 12 phases tend to convert to LuAlO 3 phases. When the Al 2 O 3 content is 78–89 mol% in the CPCs, the average grain sizes of Al 2 O 3 are close to those of Ce:LuAG. Among all CPCs with an Al 2 O 3 content of 68–95 mol%, the 85 mol% Al 2 O 3 -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 °C. A solid-state laser lighting device was constructed by using a 450 nm laser source and Al 2 O 3 -Ce:LuAG CPCs in a reflection mode. The CPCs with 85 mol% Al 2 O 3 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∙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% Al 2 O 3 -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). Al 2 O 3 -Ce:LuAG CPCs have excellent luminescence properties and improved thermal stability, which are promising for the application in solid-state laser lighting.