Synthesis and luminescence properties of Eu~(2+)- and Mn~(2+)-activated Mg_(21)Ca_4Na_4(PO_4)_(18) phosphors

摘要

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. Eu~(2+) and Mn~(2+) singly doped and Eu~(2+)/Mn~(2+)-codoped Mg_(21)Ca_4Na_4(PO_4)_(18) phosphors were synthesized for the first time via combustion-assisted synthesis technique. The Eu~(2+)-activated sample emits an intense blue light under 360 nm excitation, while the Eu~(2+)/Mn~2 -codoped Mg21Ca4Na4(PO4)18 sample exhibits a broad blue emission band and a red emission band, resulting from Eu~(2+) and Mn~(2+), respectively. Energy transfer between Eu~(2+) and Mn~(2+) was discovered and the transfer efficiency was also estimated based on relative intensities of Eu~(2+) and Mn~(2+) emission. Thus, the relative strength of blue and red emission intensities could be tuned by varying the relative concentration of Eu 2+ and Mn~(2+). Since the photoluminescence excitation spectra of the newly developed Mg_(21)Ca_4Na_4(PO_4)_(18):Eu~(2+), Mn~(2+) phosphors exhibit a strong absorption in the range of 250-400 nm, they are promising for producing UV-LED-based white LEDs.