Neutral-White Light Emission From Dy³⁺-Doped Lu₃Ga₄AlO₁₂ Nanocrystals for Ambient Lighting Applications

Trivalent dysprosium (Dy³⁺)-doped Lu₃Ga₄AlO₁₂ (LuGAG) nanocrystals with varying Dy³⁺ ion concentrations have been synthesised using the Pechini sol-gel method. To investigate their properties, the samples were analyzed using X-ray diffraction (XRD), electron microscopy (SEM and TEM), Fourier transform infrared (FTIR) spectroscopy and photoluminescence (PL) spectroscopy. XRD analysis confirmed that the samples crystallised in a garnet phase with an average crystallite size of approximately 19 nm. SEM and TEM images revealed that the particles were mostly spherical and agglomerated, with grain sizes ranging from 80 to 300 nm. When excited at 352 and 360 nm, the PL spectra displayed distinct emission peaks at 482 nm (blue), 580 nm (yellow), 671 nm (red) and 760 nm (infrared), attributed to the Dy³⁺ transitions ⁴F_9/2 → ⁶H_15/2, ⁶H_13/2, ⁶H_11/2 and ⁶H_9/2, respectively. The luminescence decay behaviour was non-exponential and could be described by the Inokuti-Hirayama model with S = 6, indicating dipole-dipole interaction-based energy transfer. The chromaticity coordinates were located in the neutral-white light region. Additionally, parameters such as colour purity, colour rendering index and correlated colour temperature were evaluated and compared with existing literature. Overall, the findings confirm that these Dy³⁺-doped LuGAG nanocrystals are promising candidates for white light emission, particularly under the 352-nm excitation.