Energy level of lanthanide ions and anomalous emission of Eu2+ in Sr3B2O6 materials

Energy level position of divalent and trivalent lanthanides in the band gap relative to the valence and conduction bands of Sr3B2O6 host lattice was determined through the f -> d transition energy of Ce3+ ion, the thermal quenching of Eu2+ emission and charge transfer energy of Eu3+. The lowest 4f -> 5d absorption transition of Tb3+ and the charge transfer energy of Sm3+, which predicted from the energy level scheme, are well matched to the observed energies from photoluminescence excitation spectra of Sm3+ and Tb3+ in Sr3B2O6 material. In addition, an anomalous emission of Sr3B2O6:Eu2+ was successfully explained by a combination of the presence of traps in lattice and the proposing energy level scheme.