Effects of Tb3+ doping on luminescence properties of NaMg4(PO4)3:Eu2+

Eu2+ and Tb3+ co-doped NaMg4(PO4)(3) phosphors have been synthesized via a combustion-assisted synthesis method. A detailed study of the role of Tb3+ concentration on the luminescence properties of Eu2+ in NaMg4(PO4)(3): Eu2+, Tb3+ has been carried out. NaMg4(PO4)(3): Eu2+, Tb3+ phosphors exhibited a broad excitation band ranging from 220 to 400 nm and two broad emission bands that peaked at 424 and 546 nm, which were ascribed to the allowed 4f(6)5d(1)-> 4f(7) transition of Eu2+ ions and the D-5(4)-> F-7(5) transition of Tb3+ ions, respectively. Initially, the emission intensity of Eu2+ decreases with increasing Tb3+ concentrations, which is related to the energy transfer (ET) from Eu2+ to Tb3+. Then, the Tb3+-doping enhances the emission intensity of Eu2+ obviously. This can be ascribed to the possible oxidation-reduction process between Eu3+ and Tb3+ to give Eu2+ and Tb4+, as confirmed by X-ray photoelectron spectroscopy and luminescence studies. The combined effects of ETEu-Tb and oxidation-reduction process between Eu3+ and Tb3+ on luminescence and emission color of NaMg4(PO4)(3): Eu2+, Tb3+ phosphors are systematically investigated.