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NAZAROV, Michael V.; BRIK, Mikhail G.; SPASSKY, Dmitry; TSUKERBLAT, Boris. Luminescence mechanism in SrAl2O4:Eu2+ phosphor. In: Materials Science and Condensed Matter Physics. Ediția a 9-a, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, p. 101.
|Materials Science and Condensed Matter Physics
Ediția a 9-a, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 25-28 septembrie 2018
The alkali earth aluminates phosphors doped by rare earth ions (especially by Eu2+) are functional inorganic materials with strong luminescence covering wide spectral range, from blue to red regions of the visible spectrum. These materials have recently attracted considerable attention, which is determined by their numerous applications, such as display devices, signage, medical application, emergency rescue guidance system, storage devices and many others. Additionally, these systems have been regarded as excellent long-persistence phosphors based on their high efficient luminescence centers and possibility to emit light long time after the excitation has ended. A stoichiometric SrAl2O4:Eu2+ nanosized powder was synthesized by combustion method using urea at 500 °C and calcinated at 1000 °C. The measurements of the luminescent properties of SrAl2O4:Eu2+ were carried out; additionally, theoretical study of the crystal field splitting of the Eu2+ 5d levels at two crystallographically different Sr positions in the SrAl2O4 lattice was performed. Two luminescence bands at 450 nm and near 520 nm were observed at lower temperatures. The luminescence mechanism and peculiar temperature dependence of bands intensities are discussed on the basis of the crystal field theory (within the exchange charge model) combined with the vibronic approach. The latter involves the electron vibrational interaction in two kinds of the Eu2+ centers as well as the interaction between these centers in the host lattice. A simplified single-mode model was adopted for each center and the section of the bi-dimensional adiabatic potential of the Eu2+ dimer along an effective ―out-of-phase mode‖ is considered. This original approach qualitatively explains the temperature dependence of the emission bands intensities by the non-radiative redistribution of excitations between two neighboring Eu2+ centers occupying two crystallographically different Sr positions in the SrAl2O4 lattice.