A Blue Light–Excited Broadband Chartreuse‐Emitting LuMg ₂ Al ₃ Si ₂ O ₁₂ :Ce ³⁺ Garnet Phosphor With High Thermal Stability for High‐Performance White LEDs

High‐brightness and thermally stable chartreuse‐emitting phosphors are highly desirable for high‐quality phosphor‐converted white light–emitting diodes (pc‐LEDs). In this article, a new chartreuse phosphor, Lu (1‐ x ) Mg 2 Al 3 Si 2 O 12 : x Ce 3+ (LMASO: x Ce 3+ ), was synthesized via a high‐temperature solid‐state reaction. X‐ray diffraction and Rietveld refinement reveal that LMASO phosphors crystallize in the cubic system (Iad). The optimal doping concentration of Ce 3+ in LMASO is 10 mol%, which is higher than that of other Ce 3+ ‐doped garnet phosphors. Its broad excitation band peaking at 429 nm matches well with the emission from commercial blue LED chips. Under 429 nm excitation, the LMASO:Ce 3+ phosphor exhibits a wide asymmetric emission band ranging from 450 to 650 nm. The high activation energy (0.334 eV) indicates a good thermal quenching resistance. A white LED device was fabricated by combining a 450nm blue LED chip with the LMASO:0.10Ce 3+ chartreuse phosphor and a commercial CaAlSiN 3 :Eu 2+ red phosphor. This device emits bright warm‐white light with excellent CIE color coordinates (0.3978, 0.3959), a low correlated color temperature (CCT = 3500 K) and a high color rendering index (Ra = 95.7). The results demonstrate that LMASO:Ce 3+ phosphor is a promising candidate for pc‐LEDs.