Highly thermal stable and color tunable composite fluorescent ceramics for high-power white LEDs

All-inorganic fluorescent materials with high luminescence efficiency, high thermal stability and adjustable spectrum are urgently needed, especially for high-power white LEDs. In this work, Y_2.84Lu_0.1Al₅O₁₂: 0.06Ce³⁺ fluorescent ceramics were prepared firstly by vacuum sintering technology, and then Y_2.84Lu_0.1Al₅O₁₂: 0.06Ce³⁺/SrAlSiN₃: Eu²⁺ composite fluorescent ceramics were synthesized by technology screen-printing and laser ablation. Under 460 nm excitation, the composite fluorescent ceramic exhibits a broad emission band from 500 nm to 675 nm, which is attributed to the 5d → 4f transitions of Ce³⁺ and Eu²⁺ ions, respectively. By controlling the screen-printed times, the color coordinates of the composite fluorescent ceramics could be tuned from (0.3125, 0.2437) to (0.4106, 0.3824), and the correlated color temperature can vary from 3296 to 9689 K. In particular, the thermal stability of composite fluorescent ceramics is improved obviously after laser ablation. At 423 K, the luminescence intensity at 535 nm and 620 remains 91% and 94% of that at room temperature, respectively. Combining a 460 nm blue chip and the composite fluorescent ceramic, a white LED with CRI = 90, and the maximum luminous efficiency can be up to 148 lm/W. Our results indicate that Y_2.84Lu_0.1Al₅O₁₂: 0.06Ce³⁺/SrAlSiN₃: Eu²⁺ composite fluorescent ceramics could be used in high-power white LEDs.