Synthesis and luminescence properties of Eu2+- and Mn2+-activated Mg21Ca4Na4(PO4)18 phosphors

Rare earth-doped phosphates have attracted much attention in recent years because of their interesting optical applications. However, few studies have reported on optical properties of fillowite-like compounds. Eu2+ and Mn2+ singly doped and Eu2+/Mn2+-codoped Mg21Ca4Na4(PO4)18 phosphors were synthesized for the first time via combustion-assisted synthesis technique. The Eu2+-activated sample emits an intense blue light under 360 nm excitation, while the Eu2+/Mn2 + -codoped Mg21Ca4Na4(PO4)18 sample exhibits a broad blue emission band and a red emission band, resulting from Eu2+ and Mn2+, respectively. Energy transfer between Eu2+ and Mn2+ was discovered and the transfer efficiency was also estimated based on relative intensities of Eu2+ and Mn2+ emission. Thus, the relative strength of blue and red emission intensities could be tuned by varying the relative concentration of Eu2+ and Mn2+. Since the photoluminescence excitation spectra of the newly developed Mg21Ca4Na4(PO4)18:Eu2+, Mn2+ phosphors exhibit a strong absorption in the range of 250–400 nm, they are promising for producing UV-LED-based white LEDs.