Ultrasonic Spray Pyrolysis Synthesis and Photoluminescence of LuAG:Ce Thin Films

LuAG:Ce (Lu₃Al₅O₁₂:Ce) is one of the most important color converters in white lighting industry. Especially, LuAG:Ce film attracts more attention due to the outstanding advantages, such as the efficient heat dissipation, the saving of rare earth, and so on. Here, LuAG:Ce film on sapphire was successfully prepared by the ultrasonic spray pyrolysis process. The phase, microstructure and photoluminescence of LuAG:Ce films were investigated. LuAG:Ce films had a thickness of around 5 μm, which were well crystallized at 1000 °C in air atmosphere to form the typical garnet structure. Under the protection of CO atmosphere, increasing the annealing temperature greatly enhanced the photoluminescence performance. After annealing at 1500 °C for 5 h in CO atmosphere, 3.0 mol.% Ce³⁺ doped LuAG:Ce film exhibited the highest emission and excitation intensity. The emission intensity of 3.0 mol.% Ce³⁺ doped LuAG:Ce film annealed at 1500 °C in CO atmosphere increased up to five times, when compared with the best LuAG:Ce film annealed at 1000 °C in air atmosphere. The effects of Ce³⁺ doping concentration on the photoluminescence were also examined. As the Ce³⁺ doping concentration increased from 0.2 mol.% to 7.0 mol.%, the color of LuAG:Ce films changed from yellowish green to greenish yellow. When coupling the 3.0 mol.% Ce³⁺ doped LuAG:Ce film with a 0.5 W 450 nm blue laser, the formed device successfully emitted white light.