Tunable luminescence of Sr5(1−x)Ba5x(PO4)3Cl:Eu2+ (0 ≤ x ≤ 100%) phosphors from different Eu2+ centers

In this paper, a series of Eu2+ activated Sr5(1−x)Ba5x(PO4)3Cl (0 ≤ x ≤ 100%) phosphors were prepared by solid-state reaction method, and their luminescence properties under near-ultraviolet excitation were investigated. For Eu2+-activated Sr5(PO4)3Cl, a strong emission band located at 445 nm is observed upon 365 nm excitation, which could be attributed to the 4f65d1–4f7 transition of different Eu2+ centers. When the Ba2+ is introduced into the Sr5(PO4)3Cl:Eu2+, the emission band of Eu2+ is broadened largely. The fluorescence lifetimes for different Eu2+ centers were determined by the decay curves and time-resolved spectra. The excitation spectra of the as-prepared samples cover a wide wavelength range from 240 to 420 nm, which can well match the emission wavelength of the near ultraviolet LED chip. The investigation of the thermal luminescence stability reveals that the introduction of Ba2+ could improve the thermal quenching properties.