SAIP 2011 Support
Synthesis and Characterization of CaAl204:Tb3+ Phosphor using Solution – Combustion Method.
Presented by Ms. Kewele Emily FOKA on 13 Jul 2011 from 17:00 to 19:00
Type: Poster Presentation
Track: Track A - Condensed Matter Physics and Material Science
<p>Presently Ca Al<sub>x</sub>O<sub>y</sub>:Tb green phosphors are mainly prepared by the solid-state process which is more feasible than others in terms of operation and large-scale production. However, the raw materials are usually not mixed well and very high temperature is needed to synthesize the final powder using the solid-state process. In order to solve these problems, Terbium ion doped calcium aluminate (Ca Al<sub>x</sub>O<sub>y</sub>:Tb<sup>3+</sup> green phosphors were obtained at low temperatures (500ºC) by the solution - combustion of corresponding metal nitrate–urea solution mixtures, over a time of 5 min. The morphology and structural properties were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), SEM shows that the particles are irregular shape and are aggregated and the structural analysis revealed the presence of monoclinic CaAl<sub>4</sub>O<sub>7</sub> at optimized fuel to nitrate molar ratio. The characteristic luminescence properties were investigated using emission spectra. It was found that the oxidizer: fuel molar ratios showed greatly influence not only on morphology, but also on their PL spectra. The photoluminescence (PL) excitation spectrum was characterized by a dominant broad band centered on 239 nm. Intense emission bands were observed at 489 nm, 544 nm, 587 nm and 622 nm originating from the <sup>5</sup> D<sub>4</sub> to <sup>7</sup> F<sub>J</sub> transition and other bands were observed at 379, 417 and 438nm originating from <sup>5</sup> D<sub>3 </sub> to <sup>7</sup> F<sub>J</sub> transition, which correspond to the crystal field splitting components of the Tb<sup>3+</sup> 4f states in Ca Al<sub>4 </sub>O<sub>7</sub>. The effects of doping concentration of Tb<sup>3+</sup> on luminescence lifetimes and intensities were also investigated. The samples with Tb concentration of 1.0 mole % exhibited the highest luminescence enhancement and longer luminescence lifetimes.
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