12-15 July 2011
Saint George Hotel
Africa/Johannesburg timezone

Enhanced green emission from UV down-converting Ce<sup>3+</sup>-Tb<sup>3+</sup> co -activated ZnAl<sub>2</sub>O<sub>4</sub> phosphor

14 Jul 2011, 09:00


Oral Presentation Track A - Condensed Matter Physics and Material Science CMPMS1


Mr Kamohelo George Tshabalala (University of the Free State)


Rare–earths (Tb3+ or Ce3+) doped zinc aluminate (ZnAl2O4) nanocrystals were successfully prepared by a modified combustion method using urea (CH4N2O, 99–99.5%) as fuel and characterized to investigate down-converted emission by energy transfer from Ce3+ to Tb3+ . The post-preparation annealing of the samples was carried out in a reducing atmosphere of 4%H2/96%N2 mixture at an elevated temperature of 7000C for 4 hours. This was meant to reduce non-emitting Ce4+ to Ce3+ and also to improve crystallinity. As confirmed by X-ray diffraction (XRD) data, the materials were highly crystalline and the XRD patterns were consistent with the closed-packed face centered cubic spinel structure of ZnAl2O4. The photoluminescence excitation and photoluminescence data collected when ZnAl2O4:Ce3+,Tb3+ samples, with different concentrations of Ce3+ and Tb3+ ions, were excited at different wavelengths (230―325nm) showed that green emission of Tb3+ was sensitized by Ce3+, i.e. there was energy transfer from Ce3+ to Tb3+ resulting in improvement of green emission due to the 5D47F5 transitions of Tb3+ ions. This study therefore, sets out to discuss the sensitizing effect of Ce3+ and the effect of post annealing on the structure of ZnAl2O4:Ce3+,Tb3+. The results indicate the potential of the phosphor powders for applications in luminescent display panels and further development as UV down-converters for improved performance of conventional photovoltaic cells.

Consider for a student <br> &nbsp; award (Yes / No)? Yes
Level (Hons, MSc, <br> &nbsp; PhD, other)? PhD
Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)? Yes

Primary authors

Mr Kamohelo George Tshabalala (University of the Free State) Prof. Odireleng Martin Ntwaeaborwa (University of the Free State)


Prof. Hendrick Swart (University of the Free State) Dr Jung-Ku Park (Korea Institute of Science and Technology (KIST)) Dr So-Hye Cho (Korea Institute of Science and Technology (KIST))

Presentation Materials