Luminescence and Microstructural Features of Eu-Activated LiBaPO4 Phosphor

Eu2+-activated LiBaPO4 phosphor was synthesized by conventional solid-state reaction. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities (12-450 K), and decay curves of the phosphor were investigated. With the increasing of temperatures, the emission bands of LiBaPO4:Eu2+ show the abnormal blue-shift and the decreasing of emission intensity. The natures of the Eu2+ emission in LiBaPO4, for example, the luminescence quenching temperature, and the activation energy for thermal quenching (Delta E), were reported. The afterglow fluorescence was detected in LiBaPO4:Eu2+ phosphor. Together with the Eu2+ luminescence, Eu3+ ions with the abnormal crystal field were observed. The site-selective excitation in the D-5(0) -> F-7(0) region for Eu3+ ions, emission spectra, and decay curves have been investigated using a pulsed, tunable, and narrowband dye laser to detect the microstructure and crystallographic surrounding of Eu-3+,Eu-2+ at Ba2+ sites in LiBaPO4. The multiple sites structure of Eu2+ and Eu3+ ions in LiBaPO4 lattices was suggested. The lower quenching temperature, afterglow, and luminescence mechanism were discussed. The photoluminescence quantum efficiencies of LiBaPO4:Eu2+ were measured and compared with the reported phosphors. Different from the published data on LiBaPO4:Eu2+, this investigation indicates that LiBaPO4:Eu2+ is not a good phosphor candidate applied in white light emitting diode.