Broadband-Emitting NaGdSiO₄:Eu^2+/3+ Phosphor for White Light-Emitting Diodes

White light-emitting diodes (LEDs) demand phosphors with efficient near-ultraviolet (NUV) excitation and high color rendering. Herein, NaGdSiO₄:Eu^2+/3+ phosphors were synthesized via a high-temperature solid-state method. Under 365/396 nm NUV excitation, they exhibit a broadband yellow emission (470-740 nm, 545 nm peak, a full-width at half maximum (FWHM) of 140 nm) from Eu²⁺ occupying Na⁺ and Gd³⁺ sites, complemented by Eu^{3 +}'s red sharp peaks. The phosphors show homogeneous elemental distribution. Introduction of Li₂CO₃ as flux enhances emission intensity and thermal stability, obviously. A prototype pc-LED device (365 nm chip + NaGdSiO₄:Eu^2+/3+ + BAM:Eu²⁺) achieves a high color-rendering index (CRI = 91.7), outperforming commercial Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺)-based LEDs (CRI = 74.6). These results demonstrate NaGdSiO₄:Eu^2+/3+'s potential as a high-CRI phosphor for high-quality white LEDs.