Synthesis, Luminescence, and Energy-Transfer Properties of β-Na_2Ca_4(PO_4)_2(SiO_4):A (A = Eu~(2+), Dy~(3+), Ce~(3+)/Tb~(3+)) Phosphors

摘要

A series of β-Na_2Ca_4(PO_4)_2(SiO_4) (β-NCPS):A (A = Eu~(2+), Dy~(3+), Ce~(3+)/Tb~(3+)) phosphors were prepared via a high-temperature solid-state reaction route. The X-ray diffraction, Fourier transform infrared, photoluminescence (PL), cathodoluminescence (CL) properties, fluorescent lifetimes, and absolute quantum yield were exploited to characterize the samples. Under UV radiation, the β- NCPS:Eu~(2+) phosphors present bright green emissions, and the β-NCPS:Ce~(3+) phosphors show strong blue emissions, which are attributed to their 4f~65d~1 → 4f~7 and 5d-4f allowed transitions, respectively. The β-NCPS:Ce~(3+), Tb~(3+) phosphors display intense tunable color from blue to green and high absolute quantum yields (81% for β-NCPS:0.12Ce~(3+) and 83% for β-NCPS:0.12Ce~(3+), 0.08Tb~(3+)) when excited at 365 nm. Simultaneously, the energy transfer from Ce~(3+) to Tb~(3+) ions is deduced from the spectral overlap between Ce~(3+) emission and Tb~(3+) excitation spectra and demonstrated by the change of emission spectra and decay lifetimes. Moreover, the energy-transfer mechanism from Ce~(3+) to Tb~(3+) ions is confirmed to be exchange interaction according to the discussion of expression from Dexter and Reisfeld. Under a low-voltage electron-beam excitation, the β-NCPS:A (A = Eu~(2+), Dy~(3+), Ce~(3+)/Tb~(3+)) phosphors exhibit their characteristic emissions, and the emission profiles of β- NCPS:Ce~(3+),Tb~(3+) phosphors are obviously different from those of the PL spectra; this difference might be ascribed to their different luminescence mechanisms. These results in PL and CL properties suggest that β-NCPS:A (A = Eu~(2+), Dy~(3+), Ce~(3+)/Tb~(3+)) phosphors are potential candidates for solid-state lighting and field-emission displays.