Luminescence and electron paramagnetic resonance investigation on ultraviolet emitting Gd doped MgAl2O4 phosphors

Phosphor powders of Gd doped MgAl2O4 have been prepared by a simple combustion route in a short time of 5 min. Powder X-ray diffraction, scanning electron microscope and energy dispersive analysis of X-ray techniques were used to characterize the as-prepared combustion product. The luminescence of Gd3+ doped MgAl2O4 shows two emission bands centered at 306 nm (6P5/2→8S7/2) and 312 nm (6P7/2→8S7/2), under UV light excitation (273 nm). Electron Paramagnetic Resonance (EPR) spectra reveal the U spectrum which is typical for Gd3+ ions disposed in tetrahedral, octahedral or cubic symmetry with moderate distortion. The number of spins, Gibbs energy, magnetic susceptibility, Curie constant and effective magnetic moment values are determined at 110 and 296 K. The linewidth is found to increase with the decrease of temperature and this has been attributed to spin–spin interaction.