Realization of color hue tuning via efficient Tb3+–Mn2+ energy transfer in Sr3Tb(PO4)3:Mn2+, a potential near-UV excited phosphor for white LEDs

Abstract

A n-UV convertible phosphor Sr3Tb(PO4)3:Mn(2+) with tunable-emitting color has been synthesized by solid state reaction. The GSAS refinement shows that the obtained powder crystallizes as a cubic unit cell with space group I43d, and Mn(2+) ions occupy the Sr(2+) crystallographic sites. Under (7)F6→(5)D3 of Tb(3+) excitation at 381 nm, Sr3Tb(PO4)3:Mn(2+) not only exhibits (5)D4→(7)F6-3 of Tb(3+) green emission lines but also (4)T1→(6)A1 of the Mn(2+) orange emission band. In addition, the intensity ratio of the orange/green emission bands can be enhanced through the increase of Mn(2+) content. The intense orange emission band of the Mn(2+) ions is attributed to the efficient energy transfer from the Tb(3+) to Mn(2+) ions, which has been justified through the luminescence spectra and fluorescence decay dynamics. The energy transfer mechanism was demonstrated to be the electric dipole-dipole interaction based on the Inokuti-Hirayama theoretical model, and the energy transfer efficiency was calculated. Optimal-composition samples show high external quantum efficiency, up to 59.3%, indicating the potential of the powder as a n-UV convertible phosphor for white LEDs.