Tb3+ induced orange persistent luminescence in Cs2CaP2O7:Eu2+: The role of the auxiliary codopant

This study reports an orange emitting persistent phosphor Cs2CaP2O7:Eu2+,Tb3+. The material was synthesized by solid state reaction method in a reducing atmosphere. The persistent phosphor was characterized in detail by X-ray powder diffraction, photoluminescence, persistent luminescence and thermoluminescence spectra. After UV irradiation, Cs2CaP2O7:Eu2+,Tb3+ phosphor shows an orange persistent luminescence (similar to 590 nm) at room temperature, whereas only photoluminescence is observed in Eu2+ singly doped samples. Both of the photoluminescence and persistent luminescence is due to the 4f(6)5d(1)-> 4f(7) transition of Eu2+ and the emission lines of Tb3+ are totally absent. The deconvolution of the thermoluminescence curve reveals there are two kinds of traps responsible for the persistent luminescence. The depth of the dominating trap is 0.61 eV. Based on experimental results, the role of Tb3+ and the trapping/detrapping processes of charge carriers were discussed. An energy level scheme was proposed to explain the mechanisms of persistent luminescence as well as photoluminescence. (C) 2017 Elsevier Ltd. All rights reserved.