Optical and structural properties of the Fe³⁺-doped Lu₃Al₅O₁₂:Ce³⁺ garnet phosphor

A novel series of Lu₃Al₅₋ₓFeₓO₁₂:Ce³⁺ (0.00 ≤ x ≤ 0.45) garnets were obtained by the solid-state reaction method at 1200 °C. The obtained materials were characterized by X-ray diffraction, Rietveld refinement, UV-Vis diffuse reflectance spectroscopy, absorption spectroscopy, and photoluminescence spectroscopy. Fe³⁺ doping allowed obtaining pure-phase materials at temperatures and times below those reported up to now. On the other hand, the materials reached an improved blue absorption and a tunable emission from green to orange. These optical properties are attributable to a red-shift phenomenon due to an increase of the crystal field splitting in the Ce³⁺ energy-levels. Moreover, the obtained phosphors exhibited a high quantum yield (55–67%), excellent thermal photoluminescence stability (up to 200 °C), and high color conversion, making the obtained phosphors promising candidates for w-LEDs.