Fabrication and enhanced photoluminescence properties of $$hbox {NaLa}(hbox {MoO}_{4})_{2}$$: $$hbox {Sm}^{3+}$$Sm3+, $$hbox {Bi}^{3+}$$Bi3+ phosphors with high efficiency white-light-emitting

The tetragonal scheelite-type (hbox {Sm}^{3+}hbox {/Bi}^{3+}) ions co-doped with (hbox {NaLa}(hbox {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 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 (hbox {MoO}_{4}^{2-}) group or (hbox {Bi}^{3+}) ions to (hbox {Sm}^{3+}) ions was established by PL investigation excited at 405 nm. The PL intensity of the studied materials was investigated as a function of different (hbox {Sm}^{3+}) and (hbox {Bi}^{3+}) concentrations. The PL investigations revealed that the phosphors exhibit apparent characteristic emissions, which is ascribed to the transition from the ground state energy level (^{4}hbox {G}_{5/2}) to excited state energy levels (^{6}hbox {H}_{mathrm{J}}) ((J= 5/2, 7/2, 9/2)) and the (hbox {NaLa}(hbox {MoO}_{4})_{2}): 4 mol% (hbox {Sm}^{3+}) and (hbox {NaLa}(hbox {MoO}_{4})_{2}): 4 mol% (hbox {Sm}^{3+}), 8 mol% (hbox {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% ((hbox {NaLa}(hbox {MoO}_{4})_{2}): 4 mol% (hbox {Sm}^{3+})) and 52% ((hbox {NaLa}(hbox {MoO}_{4})_{2}): 4 mol% (hbox {Sm}^{3+}), 8 mol% (hbox {Bi}^{3+})), respectively.