New red emitting phosphors NaSrLa(MO4)3:Eu3+ [M = Mo and W] for white LEDs: Synthesis, structural and optical study

A series of Eu3+ doped NaSrLa(MO4)3 (M = Mo and W) stable red-emitting phosphors were synthesized and their structural properties were analyzed systematically. Rietveld refinement analysis of the phosphors confirms that all the phosphors crystallizing in a tetragonal phase with space group I41/a. In addition, in order to understand more about the structural parameters, Raman spectra for the NaSrLa(MoO4)3, NaSrLa(WO4)3 and Eu substituted lattices were executed. The optical properties of all the phosphors were shown intense red emission (electric dipole (ED) transition). Temperature-dependent PL measurements exposed that NaSrLa0.2Eu0.8(MoO4)3 retains 66.13% of PL efficiency at 150 °C. The absolute quantum yield of the selected (NaSrLa0.2Eu0.8(MoO4)3 and NaSrEu(WO4)3) phosphors show 83% and 64.9% under excitation at 394 nm, respectively. The red LEDs were fabricated for the selected phosphors with the near UV LED chip (395 nm) operated at 20 mA forward bias. The results indicate that the synthesized phosphors can act as a promising red phosphor for use in near UV-pumped white LEDs.