Photoluminescence in sol–gel-derived YAG:Ce phosphors

Cerium-doped yttrium aluminium garnet (Y3Al5O12, YAG) microcrystals were grown using sol–gel technique. The samples were characterized by application of X-ray diffraction (XRD), photoluminescence (PL) spectroscopy and frequency-domain fluorescence lifetime measurements. The PL output, which is important for wavelength conversion in white light emitting diodes (LEDs), was studied as a function of Ce content and annealing temperature. XRD analysis evidenced that sintering of polycrystalline Y3Al5O12:Ce powders at 1000 °C results in the formation of monophasic garnet materials up to 10 mol% of Ce doping; however, concentration quenching is observed in samples with the Ce content exceeding ∼4% probably due to optical losses in the tail states of the imperfect lattice. PL output increased and the concentration quenching disappeared when a higher sintering temperature of 1300 °C was used. However, in high Ce content (>4%) samples, the increase in sintering temperature was found to result in the formation of CeO2 phase accompanied by an uncontrolled bouncing of PL intensity in powders with similar Ce content.