Optimizing white light luminescence in Dy³⁺-doped Lu₃Ga₅O₁₂ nano-garnets

Trivalent dysprosium-doped Lu₃Ga₅O₁₂ nano-garnets have been prepared by sol-gel method and characterized by X-ray powder diffraction, high-resolution transmission electron microscopy, dynamic light scattering, and laser excited spectroscopy. Under a cw 457 nm laser excitation, the white luminescence properties of Lu₃Ga₅O₁₂ nano-garnets have been studied as a function of the optically active Dy³⁺ ion concentration and at low temperature. Decay curves for the ⁴F_9/2 level of Dy³⁺ ion exhibit non-exponential nature for all the Dy³⁺ concentrations, which have been well-fitted to a generalized energy transfer model for a quadrupole-quadrupole interaction between Dy³⁺ ions without diffusion. From these data, a simple rate-equations model can be applied to predict that intense white luminescence could be obtained from 1.8 mol% Dy³⁺ ions-doped nano-garnets, which is in good agreement with experimental results. Chromaticity color coordinates and correlated color temperatures have been determined as a function of temperature and are found to be within the white light region for all Dy³⁺ concentrations. These results indicate that 2.0 mol% Dy³⁺ ions doped nano-garnet could be useful for white light emitting device applications