Second-Sphere Polyhedron-Distortion-Induced Broadened and Red-Shifted Emission in Lu3(Mg x Al2–x )(Al3–x Si x )O12:Ce3+ for Warm WLED

Orange-yellow phosphors with extended broadband emission are highly desirable for warmer white-light-emitting diodes (WLED) with a higher color-rendering index. Targeted phosphors Ce3+-doped Lu3(Mg x Al2–x )­(Al3–x Si x )­O12 (x = 0, 0.25, 0.50, 0.75, and 1.00) were developed by chemical composition modification for luminescent tuning from green to orange-yellow with spectral broadening. The correlation between structure evolution and luminescent properties was elucidated by the local structure, fluorescence lifetime, and Eu3+ luminescence as a structural probe. The polyhedron distortion in the second-sphere coordination leads to the site differentiation and symmetry degradation of Ce3+ with the accommodation of (MgSi)6+ pairs, comprehensively resulting in the red shift (540 → 564 nm) and broadening in emission spectra. The WLED fabrication results demonstrate that the red shift and broadening in the emission of Lu3(Mg x Al2–x )­(Al3–x Si x )­O12:Ce3+ make it more suitable for the single-phosphor converted warm WLED.