AVS 58th Annual International Symposium and Exhibition
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuP

Paper AS-TuP23
Enhanced Green Emission from UV Down-Converting Ce3+- Tb3+ Co-Activated ZnAl2O4 Phosphor

Tuesday, November 1, 2011, 6:00 pm, Room East Exhibit Hall

Session: Applied Surface Science Poster Session
Presenter: Odireleng Ntwaeaborwa, University of the Free State, South Africa
Authors: K.G. Tshabalala, University of the Free State, South Africa
S. Cho, Korea Institute of Science and Technology, Republic of Korea
J. Park, Korea Institute of Science and Technology, Republic of Korea
H.C. Swart, University of the Free State, South Africa
O.M. Ntwaeaborwa, University of the Free State, South Africa
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Ce3+-Tb3+ co-activated ZnAl2O4 nanocrystal phosphors were prepared by a solution combustion method using urea (CH4N2O, 99.0–99.5%) as a fuel. The samples were annealed at 700°C for 4 hrs, in a tabular furnace, in a reducing atmosphere containing a mixture of 4%H2 and 96%N2. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) data showed that a well known cubic normal spinel structure of ZnAl2O4 was crystallized. In addition, the HRTEM data showed that the particles were spherical with some degree of faceting. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used respectively to analyze the chemical composition of the phosphors and electronic states of individual elements. The XPS data demonstrated that there was structural readjustment of ZnAl2O4 from normal to spinel inversion due to annealing. An enhanced down-converted green emission associated with the 5D4→7F5 transitions of Tb3+ was observed at 543 nm from the ZnAl2O4:Ce3+, Tb3+ powders with different concentrations of Ce3+ and Tb3+. It was confirmed from the fluorescence decay data that the enhancement was due to energy transfer from Ce3+ to Tb3+ ions. Possible mechanism of UV down-conversion will be discussed. In addition, cathodoluminescence (CL) intensity degradation was evaluated for possible application of this material as a green emitting phosphor in field emission displays.