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

Abstract A family of apatite-type fluorophosphate phosphors with general formula Sr 3 Gd (1- m - n ) Na(PO 4 ) 3 F: m Tb 3+ , n Eu 3+ (SGN: m Tb 3+ , n Eu 3+ ) have been synthesized via the high-temperature solid-state reaction method. Triple energy transfer processes from Gd 3+ in the host to both Tb 3+ and Eu 3+ , as well as from Tb 3+ to Eu 3+ have been verified by the photoluminescence spectra. Under the excitation of UV light, both green line from the transitions of Tb 3+ and red line origin from the transitions of Eu 3+ 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 Eu 3+ content ( n ) in SGN:0.20Tb 3+ , n Eu 3+ phosphors. Additionally, the energy transfer from the Tb 3+ to the Eu 3+ 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 Eu 3+ concentration.