The Preparation and Optical Properties of Novel LiLa(MoO(4))(2):Sm(3+),Eu(3+) Red Phosphor

Novel LiLa(1−x−y)(MoO(4))(2):xSm(3+),yEu(3+) (in short: LL(1−x−y)M:xSm(3+),yEu(3+)) double molybdate red phosphors were synthesized by a solid-state reaction at as low temperature as 610 °C. The optimal doping concentration of Sm(3+) in LiLa(1−x)(MoO(4))(2):xSm(3+) (LL(1−x)M:xSm(3+)) phosphor is x = 0.05 and higher concentrations lead to emission quenching by the electric dipole—electric dipole mechanism. In the samples co-doped with Eu(3+) ions, the absorption spectrum in the near ultraviolet and blue regions became broader and stronger than these of the Sm(3+) single-doped samples. The efficient energy transfer from Sm(3+) to Eu(3+) was found and the energy transfer efficiency was calculated. Under the excitation at 403 nm, the chromaticity coordinates of LL(0.95−y)M:0.05Sm(3+),yEu(3+) approach to the NTSC standard values (0.670, 0.330) continuously with increasing Eu(3+) doping concentration. The phosphor exhibits high luminous efficiency under near UV or blue light excitation and remarkable thermal stability. At 150 °C, the integrated emission intensity of the Eu(3+) remained 85% of the initial intensity at room temperature and the activation energy is calculated to be 0.254 eV. The addition of the LL(0.83)M:0.05Sm(3+),0.12Eu(3+) red phosphors can improve the color purity and reduce the correlated color temperature of WLED lamps. Hence, LL(1−x−y)M:xSm(3+),yEu(3+) is a promising WLED red phosphor.