Structural and luminescence properties of Ho(3+)/Yb(3+)-doped Lu3Ga5O12 nano-garnets for phosphor applications

Lu3Ga5O12 nano-garnet powders doped with Ho(3+)/Yb(3+) ions have been prepared using a citrate sol-gel technique. The structural and morphological properties have been investigated by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The materials are found to exist in single phase of cubic garnet structure with an average particle size of around 45 nm. The Ho(3+)/Yb(3+)-doped Lu3Ga5O12 nano-garnet powders give rise to an intense green and weak red emission of Ho3+ ions under 457.5 nm direct excitation. Moreover, when the Yb3+ ions are excited at 950 nm a very bright green luminescence of the Ho3+ ions is observed by the naked eyes even for such low laser power as 10 mW and the intensity of the red emission have been increased compared to that found under direct excitation of the Ho3+ ions. The power dependency and dynamics of the infrared-to-visible upconverted luminescence confirm the existence of different two-photon energy transfer processes. All these results have been compared with those obtained for other garnets doped with similar lanthanide ions which suggest that the Lu3Ga5O12 nano-garnets are potential materials for light emitting devices.