Synthesis and photoluminescence properties of novel highly thermal-stable red-emitting Na3Sc2(PO4)3:Eu3+ phosphors for UV-excited white-light-emitting diodes

Abstract

A series of novel Na3Sc2(PO4)3:Eu3+ phosphors with different Eu3+ doping concentrations were synthesized by conventional solid-state method and their crystal structure, morphology, luminescence properties, temperature-dependent emission spectra, decay curves and quantum efficiency were investigated in detail. Under near-ultraviolet excitation at 394 nm, all samples exhibited strong red emissions peaking at 593, 621, 654, and 699 nm, corresponding to the characteristic 5D0→7F1,2,3,4 transitions of Eu3+ ions. From the concentration-dependent photoluminescence studies of Na3Sc2(PO4)3:Eu3+ phosphors, the optimal doping concentration of Eu3+ ions was found to be 35 mol% and the concentration quenching mechanism was dominated by dipole-dipole interactions. More importantly, the emission intensity of Na3Sc2(PO4)3 phosphors was about 6.17 times stronger than that of commercial red phosphor Y2O2S:Eu3+. Furthermore, the prepared Na3Sc2(PO4)3:0.35Eu3+ sample also possessed good colour coordinates of (0.642, 0.353) and its internal quantum efficiency was measured to be 49%. The temperature-dependent emission spectra suggested that the resultant products possessed excellent thermal stability, and the activation energy was determined to be 0.23 eV. These good results indicate that the Na3Sc2(PO4)3:Eu3+ phosphors are very appropriate red-emitting phosphors for applications in near-ultraviolet-excited white light-emitting diodes.