Role of Dy3+ → Sm3+ energy transfer in the tuning of warm to cold white light emission in Dy3+/Sm3+ co-doped Lu3Ga5O12 nano-garnets

Abstract

Nano-crystalline lutetium gallium garnets co-doped with Dy³⁺ and Sm³⁺ ions have been synthesized via a sol–gel method and their structural, morphological and luminescence properties have been characterized. All the garnets have been crystallized in a single phase of cubic structure, with an average size of 40 nm, with coral shape morphology. Under different excitation wavelengths, the nano-garnets exhibit the strong yellow and blue emissions of Dy³⁺ ions, as well as the orange and red emissions of Sm³⁺ ions. In Dy³⁺/Sm³⁺ co-doped Lu₃Ga₅O₁₂ nano-garnets, white light emission has been tuned from warm to cool by varying the concentration of Sm³⁺ ions, as well as the excitation wavelength. The color coordinates for 2 mol% Dy³⁺/10 mol% Sm³⁺ co-doped nano-garnets have been found to be (0.317, 0.321), quite close to ideal white light, with a correlated color temperature of 6322 K under 351 nm excitation. Moreover, decay times, multipolar interactions, and energy transfer parameters for excited states of Dy³⁺ and Sm³⁺ ions in co-doped nano-garnets have been evaluated to derive the relationship between the doping concentration and luminescence properties. These results reveal that the studied nano-garnets could be a potential candidate for white light emitting device applications.