Fabrication and enhanced photoluminescence properties of NaLa(MoO4)2: Sm3+, Bi3+ phosphors with high efficiency white-light-emitting

Abstract

The tetragonal scheelite-type Sm3+/Bi3+ ions co-doped with NaLa(MoO4)2 phosphors were synthesized by a facile sol-gel and combustion process using citric acid as complexing agent. The crystal structure and morphology of these as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, UV-absorption and the photoluminescence (PL) properties of these phosphors were systematically investigated and the PL of the phosphors shows strong white light emissions. Efficient energy transfer from the MoO2- 4 group or Bi3+ ions to Sm3+ ions was established by PL investigation excited at 405 nm. The PL intensity of the studied materials was investigated as a function of different Sm3+ and Bi3+ concentrations. The PL investigations revealed that the phosphors exhibit apparent characteristic emissions, which is ascribed to the transition from the ground state energy level 4G5/2 to excited state energy levels 6HJ (J = 5/2, 7/2, 9/2) and the NaLa(MoO4)2: 4 mol% Sm3+ and NaLa(MoO4)2: 4 mol% Sm3+, 8 mol% Bi3+ present white emissions with the CIE coordinates of (0.350, 0.285) and (0.285, 0.229), respectively. The absolute quantum efficiencies of the phosphors are 40% (NaLa(MoO4)2: 4 mol% Sm3+) and 52% (NaLa(MoO4)2: 4 mol% Sm3+, 8 mol% Bi3+), respectively.