Tunable emission, energy transfer, and thermal stability of Ce3+-doped and Ce3+/Tb3+ Co-doped Ca9Sr(PO4)6Cl2 phosphors

Abstract

Ce3+-doped and Ce3+/Tb3+ co-doped Ca9Sr(PO4)6Cl2 phosphors were synthesized successfully via a traditional high-temperature solid-state reaction. The crystal structure, photoluminescent properties including temperature-dependent luminescence, and energy transfer of the as-prepared phosphors were investigated. The as-prepared Ca9Sr(PO4)6Cl2:Ce3+ phosphors exhibit a broad excitation band ranging from 220 to 385 nm and blue light-emitting band centered at 431 nm, which originate from the 4f–5d transitions of Ce3+ ion. The luminescent intensities of Tb3+ ions were dramatically enhanced by the introduction of Ce3+ in the Ca9Sr(PO4)6Cl2:Tb3+ phosphors because of the efficient energy transfer from Ce3+ to Tb3+ ions, generating tunable blue-green emission colors. The mechanism of energy transfer between Ce3+ and Tb3+ ions was demonstrated to be an electric dipole–quadrupole interaction. Moreover, the energy transfer efficiency was evaluated up to 75 % based on the analysis of the emission spectra. The temperature-dependent photoluminescence indicates that the as-prepared Ce3+/Tb3+ co-doped Ca9Sr(PO4)6Cl2 phosphors have excellent thermal stability. Our results suggest that the Ce3+-doped and Ce3+/Tb3+ co-doped Ca9Sr(PO4)6Cl2 phosphors have potential application for n-UV pumped WLEDs.