Speaker
Description
Presently Ca AlxOy: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 AlxOy:Tb3+ 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 CaAl4O7 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 5 D4 to 7 FJ transition and other bands were observed at 379, 417 and 438nm originating from 5 D3 to 7 FJ transition, which correspond to the crystal field splitting components of the Tb3+ 4f states in Ca Al4 O7. The effects of doping concentration of Tb3+ 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.
| Level (Hons, MSc, <br> PhD, other)? | Msc |
|---|---|
| Consider for a student <br> award (Yes / No)? | Yes |
| Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)? | Yes |
