Triple energy transfer and color tuning in Tb3+ and Eu3+-coactivated apatite-type gadolinium-containing phosphors

A family of apatite-type fluorophosphate phosphors with general formula Sr3Gd(1-m-n)Na(PO4)(3)F:mTb(3+),nEu(3+) (SGN:mTb(3+),nEu(3+)) have been synthesized via the high-temperature solid-state reaction method. Triple energy transfer processes from Gd3+ in the host to both Tb3+ and Eu3+, as well as from Tb3+ to Eu3+ have been verified by the photoluminescence spectra. Under the excitation of UV light, both green line from the transitions of Tb3+ and red line origin from the transitions of Eu3+ have been simultaneously observed in a single phase phosphor, which makes a promise for tunable color emissions from yellowish-green through yellow and ultimately to reddish-orange by simply adjusting the Eu3+ content (n) in SGN:0.20Tb(3+),nEu(3+) phosphors. Additionally, the energy transfer from the Tb3+ to the Eu3+ ions has been demonstrated to be a resonant type via a quadrupole quadrupole mechanism based on the Dexter's theoretical model, and the energy transfer efficiency increases with an increase in Eu3+ concentration. (C) 2017 Elsevier B.V. All rights reserved.