Efficient red phosphors Na₅Ln(MoO₄)₄ : Eu³⁺(Ln = La, Gd and Y) for white LEDs

Abstract

A class of red-emitting phosphors Na5Ln(MoO4)4 : Eu3+(Ln = La, Gd and Y) have been synthesized by the sol–gel technique and their luminescent properties have also been investigated under the near-ultraviolet (n-UV) light. The excitation spectra of these phosphors show the strongest absorption at about 395 nm which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show intense red emission at 618 nm due to the 5D0–7F2 transition of Eu3+. The phosphor Na5Y1−xEux(MoO4)4 shows the brightest red light among phosphors Na5Ln1−xEux(MoO4)4 as the content of Eu3+ is fixed. In addition, the conditions for synthesis of these phosphors are also optimized, including annealing temperature and concentration of Eu3+ ions. While the Li+ or K+ ions are incorporated into Na5Eu(MoO4)4 to substitute for Na+ partially, effects on the luminescent properties and structures of phosphors have also been discussed in detail.