Photo-induced charge state conversion of Eu2+ in Ca2 ZnSi2 O7

Abstract

Eu2+ doped sorosilicate Ca2 ZnSi2 O 7 (melilite) exhibits a broad band emission peaking at ∼600 nm (∼2 eV) due to the electric dipole allowed transition of 4 f6 5 d1 to 4 f7 of Eu2+ by an excitation with blue light (460 nm). Strong O2- ligand field with low symmetry due to the layered tetragonal crystallographic structure of the melilite may play a dominant role in lowering the emission band energy to ∼2 eV. In addition, line emissions attributable to the transitions from D05 to FJ7 of Eu3+ ions are detected by an excitation with deep UV light with sub-360 nm wavelengths. This is due to the formation of transient Eu3+ ions via charge transfer from Eu2+ to the matrix. The lifetime of the transient Eu3+ ion is found to be 58 ms by a pump-probe measurement, in which UV pulse laser and green continuous wave laser are employed as pump and probe lights, respectively. Based on these results, the energy diagram of Eu2+ in Ca2 ZnSi 2 O7 is proposed. © 2009 American Institute of Physics.