Tunable correlated color temperature of NaSrPO4 phosphors via Dy3+ and Eu3+ co-doping for warm white light-emitting diodes

Correlated color temperature (CCT) of NaSrPO4 phosphors were tuned through the co-doping of Dy3+ and Eu3+. The pure and doped NaSrPO4 phosphors were synthesized by a high temperature solid-state sintering method. The crystal structure and luminescent properties of the phosphors were studied. NaSrPO4:Dy3+ phosphors exhibit two emission peaks at 481 and 576 nm, originating from the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, while two new emission peaks at 590 and 612 nm originating from the transitions of 5D0→7FJ (J = 1, 2) of Eu3+ appear for NaSrPO4:Dy3+, Eu3+. With the changing Eu3+ doping concentration from 0 to 0.07, the emission light of NaSrPO4:Dy3+, Eu3+ changes from bluish white (CCT: 10,150 K) to reddish white (CCT: 5186 K). Furthermore, the energy transfer phenomenon from Dy3+ ions to Eu3+ ions in Dy3+, Eu3+ co-doped NaSrPO4 phosphors was also investigated. All in all, the NaSrPO4:Dy3+, Eu3+ phosphors are a new kind of full color single phase warm white emitting phosphors for near ultraviolet pumped warm white light-emitting diodes.