A new type of phosphate-based phosphor Na 3 CsMg 7 (PO 4 ) 6 :Eu 2+ /Mn 2+ with high quantum efficiency and high thermostability.

The Eu 2+ ion, with the 4f 7 5d 1 electronic configuration, is one of the most important activated ions due to its symmetry-allowed 4f → 5d electron transition. Herein, we successfully prepared a new type of blue phosphor, Na 3 CsMg 7 (PO 4 ) 6 : x Eu 2+ (NCMP: x Eu 2+ ), in which Eu 2+ occupies the Na + sites of the host lattice. Under 395 nm light excitation, a broad emission band from 410 to 550 nm can be seen, peaking at 458 nm, due to the 5d → 4f transition of Eu 2+ . Moreover, Eu 2+ can be used as a sensitizer ion in an NCMP host. For co-doping phosphor NCMP:0.18Eu 2+ /0.4Mn 2+ , both Eu 2+ and Mn 2+ emission bands can be seen using 395 nm as the excitation wavelength for the occurrence of Eu 2+ → Mn 2+ charge transfer. The optimized concentration of Eu 2+ for NCMP: x Eu 2+ is x = 0.18, with high internal (IQE) and external quantum efficiencies (EQE) of 66.4% and 22.8%. The luminescence of NCMP:0.18Eu 2+ has high thermostability with 77.3% the intensity at 450 K compared to that at 300 K. Finally, a white illuminating lamp was produced using a 395 nm UV chip, blue phosphor NCMP: x Eu 2+ , green phosphor (Sr,Ba) 2 SiO 4 :Eu 2+ and red phosphor CaAlSiN 3 :Eu 2+ with CIE coordinates of (0.378, 0.369), color temperature (CCT) of 3971 K, and color rendering index ( R a ) of 79.8.