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

Abstract

Ce³⁺-, Tb³⁺-, and Mn²⁺-activated\nCa₃Gd₇(PO₄)­(SiO₄)₅O₂ (CGPS) silicate–phosphate oxyapatite\nphosphors have been prepared via conventional solid-state reaction\nprocesses. The Ce³⁺ emission at different lattice sites\nhas 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\na resonant type via a dipole–quadrupole mechanism, and the\ncritical distances (<i>R</i>_C) for Ce³⁺ to Mn²⁺ calculated by the concentration quenching and\nspectral overlap methods are 9.71 and 9.15 Å, respectively. A\ncolor-tunable emission in CGPS phosphors can be realized by Ce³⁺ → Tb³⁺ or Ce³⁺ → Mn²⁺ energy transfer. CGPS:0.05Ce³⁺/ 0.15Tb³⁺ shows the optimum green emission. Meanwhile, white cathodoluminescence\n(CL) has been realized in a single-phased Ca₃Gd₇(PO₄)­(SiO₄)₅O₂ host by\ncodoping with Ce³⁺ and Mn²⁺ with CIE (0.322,\n0.326). Furthermore, the CL properties of CGPS:Ce³⁺/Tb³⁺/Mn²⁺ phosphors, including the dependence of the\nCL intensity on the accelerating voltage and filament current, the\ndecay behavior of the CL intensity under electron bombardment, and\nthe stability of the CIE chromaticity coordinates, have been investigated\nin detail. Because of the good CL properties and good CIE chromaticity\ncoordinates, the as-prepared phosphors have potential application\nin field emission display devices.