Blue-Light-Excited Eu3+/Sm3+ Co-Doped NaLa(MoO4)2 Phosphors: Synthesis, Characterizations and Red Emission Enhancement for WLEDs

Abstract

The system NaLa(MoO4)2:Eu3+/Sm3+ phosphors were prepared by solid-state reaction followed by heat treatment at 450–600 °C. As shown by X-ray powder diffraction, the phosphors had a body-centered tetragonal structure, high phase purity and high crystallinity. The photoluminescence measurements carried out under excitation at 464 nm indicated the main emission at about 615 nm corresponding to the electric dipole transition 5D0→7F2 of Eu3+, which agreed well with the emission wavelengths of the GaN-based blue LED chips. In NaLa(MoO4)2:Eu3+/Sm3+ phosphors, Sm3+ can efficiently transfer excitation energy to Eu3+, which resulted in a significant improvement of the fluorescence intensity, and the fluorescence intensity of the phosphors calcined at 550 °C maximized at the doping concentrations of Eu3+ and Sm3+ of 15.0 and 2.0 mol %, respectively. The decay curves and CIE (Commission Internationale de L’ Eclairage) coordinates of Sm3+ or/and Eu3+ doped phosphors were analyzed for the investigation of the energy transfer mechanism and color variation trend. Thus, NaLa(MoO4)2:Eu3+,Sm3+ can be classified as a potential red-emitting phosphor for white light-emitting diodes (WLEDs).

Temperature-Dependent Luminescence of Red-Emitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for Near-UV LEDs

“…This originates from the fact that Eu 3+ can occupy four lattice sites with each giving lines at slightly different wavelengths due to the different crystal field generated. This is the opposite to phosphors where only one lattice site is available for Eu 3+ ions and there are very few excitation lines which, in turn, are also very narrow [13,[26][27][28][29]. The absorption strength of the synthesized phosphors increased with increasing Eu 3+ concentration.…”

Tunable lanthanide/transition metal ion‐doped novel phosphors for possible application in w‐LEDs: a review

“…Yan et al . recently studied the luminescence properties of NaLa(MoO 4 ) 2 (belonging to the double molybdate family) . It typically has a tetragonal structure in which the Mo 6+ is associated with four neighbouring O 2− and forming highly stable tetrahedral MoO 4 2− anions.…”

Multicolor tunable bright photoluminescence in Ca2+/Mg2+ modified Eu3+ doped ZnGa2O4 phosphors under UV excitation for solid state lighting applications

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