Fabrication and enhanced photoluminescence properties of NaLa(MoO$_4$)$_2$: Sm$^{3+}$, Bi$^{3+}$ phosphors with high efficiency white-light-emitting

[摘要] The tetragonal scheelite-type Sm$^{3+}$/Bi$^{3+}$ ions co-doped with NaLa(MoO$_4$)$_2$ phosphors were synthesized by a facile sol–gel and combustion process using citric acid as complexing agent. The crystal structure and morphology of theseas-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 PLof the phosphors shows strong white light emissions. Efficient energy transfer from the MoO$^{2-}_4$ group or Bi$^{3+}$ ions to Sm$^{3+}$ ions was established by PL investigation excited at 405 nm. The PL intensity of the studied materials was investigated asa function of different Sm$^{3+}$ and Bi$^{3+}$ concentrations. The PL investigations revealed that the phosphors exhibit apparentcharacteristic emissions, which is ascribed to the transition from the ground state energy level 4G5/2 to excited state energylevels ${}^6$H$_J$ ($J = 5/2$, 7/2, 9/2) and the NaLa(MoO$_4$)$_2$: 4 mol% Sm$^{3+}$ and NaLa(MoO$_4$)$_2$: 4 mol% Sm$^{3+}$, 8 mol% Bi$^{3+}$ 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(MoO$_4$)$_2$: 4 mol% Sm$^{3+}$) and 52% (NaLa(MoO$_4$)$_2$: 4 mol% Sm$^{3+}$, 8 mol% Bi$^{3+}$), respectively.

[学科分类] 材料工程

[关键词] Optical properties;sol–gel processes;combustion method;photoluminescence.