Cyan-Green Phosphor (Lu₂M)(Al₄Si)O₁₂:Ce³⁺ for High-Quality LED Lamp: Tunable Photoluminescence Properties and Enhanced Thermal Stability

High-quality white light-emitting diodes (w-LEDs) are mainly determined by conversion phosphors and the enhancement of cyan component that dominates the high color rendering index. New phosphors (Lu2M)­(Al4Si)­O12:Ce3+ (M = Mg, Ca, Sr and Ba), showing a cyan-green emission, have been achieved via the co-substitution of Lu3+-Al3+ by M2+-Si4+ pair in Lu3Al5O12:Ce3+ to compensate for the lack of cyan region and avoid using multiple phosphors. The excitation bands of (Lu2M)­(Al4Si)­O12:Ce3+ (M = Mg, Ca, Sr and Ba) show a red-shift from 434 to 445 nm which is attributed to the larger centroid shift and crystal field splitting. The enhanced structural rigidity associated with the accommodation of larger M2+ leads to a decreasing Stokes shift and the corresponding blue-shift (533 → 511 nm) in emission spectra, along with an improvement in thermal stability (keeping ∼93% at 150 °C). The cyan-green phosphor Lu2BaAl4SiO12:Ce3+ enables to fabricate a superhigh color rendering w-LED (Ra = 96.6), verifying its superiority and application prospect in high-quality solid-state lightings