Low-temperature solid-state synthesis and photoluminescence properties of novel high-brightness and thermal-stable Eu3+-activated Na2Lu(MoO4)(PO4) red-emitting phosphors for near-UV-excited white LEDs

In this paper, novel Na2Lu(MoO4)(PO4):Eu3+ phosphors with different Eu3+ doping concentrations were synthesized by a low-temperature solid-state method and their crystal structure, morphology, luminescence properties, decay curves and quantum efficiency were investigated in detail. Under near-ultraviolet excitation at 396 nm, all samples exhibited strong red emissions peaking at 593, 616, 655, and 702 nm, corresponding to the characteristic D-5(0)-> F-7(1,2,3,4) transitions of Eu3+ ions. From the concentration-dependent photoluminescence studies of Na2Lu(MoO4)(PO4):Eu3+ phosphors, the optimal doping concentration of Eu3+ ions was found to be 60 mol%. The as-prepared Na2Lu(MoO4)(PO4):0.6Eu(3+) sample possessed good colour coordinates of (0.660, 0.338) with high colour purity of 93.5%. More importantly, the emission intensity of Na2Lu(MoO4)(PO4):Eu3+ phosphors was about 3.75 and 4.02 times stronger than commercial red phosphors Y2O2S:Eu3+ and Y2O3:Eu3+, respectively. The internal quantum efficiency of Na2Lu(MoO4)(PO4):0.6Eu(3+) sample was measured to be 73.1%. Furthermore, Na2Lu(MoO4)(PO4):Eu3+ exhibited good thermal stability and its emission intensity decreased slightly at temperature above 150 degrees C. These good results indicate that the Na2Lu(MoO4 )(PO4):Eu3+ phosphors are very appropriate red-emitting phosphors for applications in near-ultraviolet-excited white light-emitting diodes. (C) 2018 Elsevier B.V. All rights reserved.