Reverse effect of Sm3+ on Ce3+ in Ca2BO3Cl:Ce3+/Tb3+/Sm3+ phosphor: Luminescence, energy transfer and occupation site.

Abstract

A series of Ca2BO3Cl:Ce3+, Tb3+, Sm3+ are successfully synthesized by a high temperature solid state reaction. And the crystal structure, luminescence property and energy transfer mechanism of Ce3+/Sm3+, Tb3+/Sm3+ and Ce3+/Tb3+/Sm3+ in Ca2BO3Cl are investigated. There is an interesting phenomenon that the right side of the Ce3+ emission spectra in Ca2BO3Cl:Ce3+, Sm3+ compresses gradually with increasing the Sm3+ concentration. By means of refinement, it can be found that Sm3+ ions are mainly occupied in the Ca2 sites, because the cell of the Ca2 lattice is easily occupied. Then, the emission peak2 of Ce3+ in Ca2 sites occurs to blue shift. While the emission peak1 of Ce3+ in Ca1 sites is basically stability. However, the emission of Ce3+ in Ca2BO3Cl:Ce3+, Tb3+, Sm3+ have different changes with increasing the Sm3+ concentration that the emission peaks of Ce3+ shift to long wave at first then to short wave and the FWHM remains stability. This can be attributed to the existence of Tb3+. For the energy transfer mechanism, according to Dexter's energy transfer theory and Reisfeld's approximation, the energy transfer process of Ce3+/Sm3+ and Tb3+/Sm3+ should be the dipole-dipole interaction. And white emitting phosphor is achieved by the efficient energy transfer.