Study of Photoluminescence Properties of MgAl_2O_4 Doped With Europium Prepared by Microwave Assisted Solution Combustion Synthesis

摘要

Photo luminescent nanoparticles of MgAl_2O_4:Eu were prepared by microwave assisted solution combustion synthesis method and thermally treated at 500? C. The prepared material was characterized by X-ray diffraction, SEM, TEM and TGA-DTA whereas photoluminescence properties were studied by excitation and emission spectroscopy at room temperature. XRD pattern reveals the formation of cubic MgAl_2O_4 spinel phase with space group Fd3m and crystalline size of 40 nm being calculated from Scherrer formula. The TEM image shows that there are many irregular particles with shape close to spherical with average particle size 45 nm. TGA-DTA curve reflected the weight loss at 200? C and 500? C which may be due to evaporation of some physically absorbed water and decomposition and oxidation of metal nitrate. The photoluminescence spectra of the doped MgAl_2O_4:Eunanopowders shows intense red emission (λ_(em)= 614 nm) resulting from the ~5D_0→~7F_2transition with a maximum intensity at an excitation wavelength of 380 nm. The emission band identified at 698 nm which is due to the transition: ~5D_0→~7F_4. The transition ~5D_0→~7F_2is of an electric-dipole (ED) origin is hypersensitive to its local site symmetry. Due to lower europium content and lower annealing temperature there were no emission transitions corresponding to Eu~(2+), which usually occurs at elevated temperature.