Luminescence and Microstructural Features of Eu-Activated LiBaPO4 Phosphor

Luminescence and Microstructural Features of Eu-Activated LiBaPO₄ Phosphor
Suyin Zhang, Yosuke Nakai, Taiju Tsuboi, Yanlin Huang*, and Hyo Jin Seo*
Chem. Mater., 2011, 23 (5), pp 1216–1224

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 (ΔE), 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 ⁵D₀ → ⁷F₀ 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+,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.