A new type of phosphate-based phosphor NaCsMg(PO):Eu/Mn with high quantum efficiency and high thermostability.

The Eu ion, with the 4f5d 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, NaCsMg(PO):Eu (NCMP:Eu), in which Eu 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. Moreover, Eu can be used as a sensitizer ion in an NCMP host. For co-doping phosphor NCMP:0.18Eu/0.4Mn, both Eu and Mn emission bands can be seen using 395 nm as the excitation wavelength for the occurrence of Eu → Mn charge transfer. The optimized concentration of Eu for NCMP:Eu is = 0.18, with high internal (IQE) and external quantum efficiencies (EQE) of 66.4% and 22.8%. The luminescence of NCMP:0.18Eu 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:Eu, green phosphor (Sr,Ba)SiO:Eu and red phosphor CaAlSiN:Eu with CIE coordinates of (0.378, 0.369), color temperature (CCT) of 3971 K, and color rendering index () of 79.8.