Electronic structure of the Sr 2MgSi 2O 7:Eu 2+ persistent luminescence material

Abstract

The electronic structures of the distrontium magnesium disilicate (Sr 2MgSi 2O 7(:Eu 2+)) materials were studied by a combined experimental and theoretical approach. The UV–VUV synchrotron radiation was applied in the experimental study while the electronic structures were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands and the band gap energy of the material as well as the position of the Eu 2+ 4f ground state were calculated. The calculated band gap energy (6.7 eV) agrees well with the experimental value of 7.1 eV. The valence band consists mainly of the oxygen states and the bottom of the conduction band of the Sr states. The calculated occupied 4f ground state of Eu 2+ lies in the energy gap of the host though the position depends strongly on the Coulomb repulsion strength. The position of the 4f ground state with respect to the valence and conduction bands is discussed using the theoretical and experimental evidence available.