Spectroscopic properties and energy level location of Eu2+ in Sr2Si5N8 phosphor

Abstract In this contribution luminescence properties of Sr 2− x Si 5 N 8 :Eu x 2+ ( x = 0.02 and 0.1) at temperatures from 10 to 600 K are presented. Both materials exhibit broad band red emission assigned to the parity allowed 4f 6 5d 1 → 4f 7 transitions in Eu 2+ ions occupying two different crystallographic sites labeled as Eu(Sr1) and Eu(Sr2). For low concentration of dopants only Sr1 site is occupied, whereas for higher concentration both Sr1 and Sr2 sites are occupied. Optical data are used to construct configurational coordination diagrams of the Eu(Sr1) and Eu(Sr2) centers in Sr 2 Si 5 N 8 lattice. Effects of temperature luminescence quenching and luminescence lifetime shortening were related to ionization of Eu 2+ ions and anharmonicity of adiabatic lattice potential. Effect of non-homogeneity of the Eu 2+ occupation between the Sr1 and Sr2 sites is discussed by considering the energies of the ground states of Eu(Sr1) and Eu(Sr2) in respect to the valance and conduction bands.