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

A class of red-emitting phosphors Na 5 Ln(MoO 4 ) 4 : Eu 3+ (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 5 D 0 – 7 F 2 transition of Eu 3+ . The phosphor Na 5 Y 1− x Eu x (MoO 4 ) 4 shows the brightest red light among phosphors Na 5 Ln 1− x Eu x (MoO 4 ) 4 as the content of Eu 3+ is fixed. In addition, the conditions for synthesis of these phosphors are also optimized, including annealing temperature and concentration of Eu 3+ ions. While the Li + or K + ions are incorporated into Na 5 Eu(MoO 4 ) 4 to substitute for Na + partially, effects on the luminescent properties and structures of phosphors have also been discussed in detail.