Main supervisor (name and email)<br>and his / her institution
F.B. Dejene (University of the Free State)
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Abstract content <br> (Max 300 words)
A report on the sol-gel preparation of nanosized ZnAl2O4:Cr3+ at a relatively low temperature (~80 °C). The mol% of Cr3+ was varied in the precursor during the synthesis. The gel, dried and annealed powder samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR) and photoluminescence (PL) spectroscopy. The XRD data revealed that the dried and annealed samples consist of the mixture of ZnO, Al3O2 and cubic phases of ZnAl2O4. The estimated crystalline size for the cubic spine phase was found to be 28 nm in diameter. The surface morphology of the phosphors was influenced by the mol% of the Cr3+ in the precursor. FTIR spectra showed that the number of bands decreases when the samples are heat-treated at higher temperatures. PL spectra indicated that both undoped and Cr-doped ZnAl2O4 powders exhibit green PL emission when the powders are sintered at 700 oC in air. It indicates that the green emissions come from either the host or Cr3+ ions. However, it is noted that the green emission peaks were at different positions, 515 nm and 530 nm, for undoped and Cr-doped phosphors, respectively.
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