Facile self-propagating combustion synthesis of MgO: Eu3+ orange-red nanophosphor and luminescence investigation by Judd-Ofelt intensity parameters

In the present work we demonstrate the potential of one pot combustion derived Eu3+ doped nano MgO as efficient orange-red luminescent host. Surface morphology and size of the particles are characterized by scanning and transmission electron microscopic techniques. Optimization of the luminescence output is carried out by varying the dopant (Eu3+) concentration of Mg1−xO:xEu3+ (0.01 < x < 0.09). Upon excitation at 395 nm the emission spectra of the phosphor show sharp peaks at 542, 577, 594, 653 and 690 nm corresponding to f-f transitions of rare earth dopant. The optimal Eu3+ content was found to be x = 0.05 at which Mg1-xO:xEu3+ show enhanced sharp orange red emission. Beyond x = 0.05, concentration quenching was observed and critical distance calculations revealed the mechanism of quenching to be electric multipole-multipole interactions. Judd-Ofelt intensity parameters were calculated in order to evaluate the influence of the host lattice on the emission behaviour of the Eu3+ dopant in MgO. The branching ratios Ω2 and Ω4 were calculated and with increasing Eu3+ concentration, Ω2 was found to increase. Further, Ω2 > Ω4 indicates that the covalency of EuO bonds increases and this suggests that host lattice crystal field has significant effect on Eu3+ emission. Thermoluminescence (TL) studies performed for γ-irradiated samples and TL glow curve suggest multiple types of traps in the host. TL intensity parameters were calculated and analysed in detail to understand the applicability of the phosphor for dosimetric use.