8-12 July 2013
Blue luminescence from Bi doped MgAl2O4 prepared by the combustion method
Presented by Mr. Wael TABAZA on 9 Jul 2013 from 17:40 to 18:40
Type: Poster Presentation
Track: Track A - Division for Condensed Matter Physics and Materials
Magnesium aluminate (MgAl<sub>2</sub>O<sub>4</sub>) has received special attention as a technologically important material because of its attractive properties such as mechanical strength, chemical inertness, wide band gap, relatively low density, high melting point, high thermal shock resistance, low thermal expansion coefficient, resistance to neutron irradiation and low dielectric loss. It has also been considered as a phosphor host activated by a variety of transition metal and lanthanide ions. As an alternative to such ions, luminescence can often be obtained from the ns<sup>2</sup>-type ions such as Tl<sup>+</sup>, Pb<sup>2+</sup>, Bi<sup>3+</sup> and Sb<sup>3+</sup>. For trivalent bismuth ions luminescence is attributed to electron transitions between the 6s<sup>2</sup> ground state and the 6s6p excited states. A simple combustion method was employed for the preparation of Bi doped MgAl<sub>2</sub>O<sub>4</sub> nanocrystals using metal nitrates as precursors and urea as a fuel in a furnace preheated to 520˚C. The samples were characterized by x-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and photoluminescence spectroscopy. For an excitation wavelength of 330 nm, the Bi doped MgAl<sub>2</sub>O<sub>4</sub> produced a blue emission band centred near 410 nm, indicating that Bi<sup>3+</sup> ions were successfully incorporated in the lattice. The maximum emission intensity was obtained for the sample doped with 0.5 mol% Bi. The results indicate that doping MgAl<sub>2</sub>O<sub>4</sub> with Bi ions may be an attractive alternative to doping it with Ce ions, which give broad blue-green luminescence in this host but requires reducing at a high temperature (1400˚C) to convert non-luminescent Ce<sup>4+</sup> ions to the luminescent Ce<sup>3+</sup> charge state.
Dr RE Kroon (KroonRE@ufs.ac.za) - University of the Free State