Study of photoluminescence properties of MgAl 2 O 4 doped with europium prepared by microwave assisted solution combustion synthesis

Abstract

Photo luminescent nanoparticles of MgAl 2 O 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 2 O 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 2 O 4 :Eunanopowders shows intense red emission (λ em = 614 nm) resulting from the 5 D 0 → 7 F 2 transition with a maximum intensity at an excitation wavelength of 380 nm. The emission band identified at 698 nm which is due to the transition: 5 D 0 → 7 F 4 . The transition 5 D 0 → 7 F 2 is 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.