Structural and photo-induced properties of EU2+-doped Ca2ZnSi2O7:: A red phosphor for white light generation by blue ray excitation

We demonstrate Eu-2 divided by ion activated sorosilicate Ca2ZnSi2O7 exhibits a broad emission band centered at 600 nm due to Eu(2+)4f(6)5d(1)-> 4f(7) transition, which is compatible for a blue light (similar to 450nm) excitation. Orbital symmetry of the emitting state and the tight coordination of 8 oxygen ions in its layered structure, which enhance covalency of Eu2+ -O bonding and ligand field splitting of 5d levels, are responsible for the long wavelength emission from Eu2+ ions. In addition, the formation of a photo-induced transient Eu3+ state from Eu2+ was observed by the irradiation of UV light with an energy being slightly larger than the band gap energy of the host. A recovery life time of the EU3 divided by to Eu2+ ions is evaluated to be 11.0 ms at 77 K by a pump-probe technique. (c) 2006 Elsevier B.V. All rights reserved.