Color-Tunable Emission and Energy Transfer in Ca3Gd7(PO4)(SiO4)5O2: Ce3+/Tb3+/Mn2+ Phosphors

Ce3+-, Tb3+- and Mn2+-activated Ca3Gd7(PO4)(SiO4)(5)O-2 (CGPS) silicate-phosphate oxyapatite phosphors have been prepared via conventional solid-state reaction processes. The Ce3+ emission at different lattice sites has been identified and discussed. The dual energy transfer of Ce3+ -> Tb3+ and Ce3+ -> Mn2+ has been investigated. The energy transfer from Ce3+ to Mn2+ in CGPS phosphors has been demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distances (R-C) for Ce3+ to Mn2+ calculated by the concentration quenching and spectral overlap methods are 9.71 and 9.15 angstrom, respectively. A color-tunable emission in CGPS phosphors can be realized by Ce3+ -> Tb3+ or Ce3+ -> Mn2+ energy transfer. CGPS:0.05Ce(3+)/ 0.15Tb(3+) shows the optimum green emission. Meanwhile, white cathodoluminescence (CL) has been realized in a single-phased Ca3Gd7(PO4)(SiO4)(5)O-2 host by codoping with Ce3+ and Mn2+ with CIE (0.322, 0.326). Furthermore, the CL properties of CGPS:Ce3+/Tb3+/Mn2+ phosphors, including the dependence of the CL intensity on the accelerating voltage and filament current, the decay behavior of the CL intensity under electron bombardment, and the stability of the CIE chromaticity coordinates, have been investigated in detail. Because of the good CL properties and good CIE chromaticity coordinates, the as-prepared phosphors have potential application in field emission display devices.