Synthesis and luminescent properties of high brightness MRE(MoO_4)_2:Eu~(3+) (M = Li, Na, K; RE = Gd, Y, Lu) red phosphors for white LEDs

摘要

A series of Eu~(3+)-activated double molybdate phosphors MRE(MoO_4)_2 (M = Li, Na, K; RE = Gd, Y, Lu) have been successfully prepared via the conventional solid-state reaction method. The effects of alkali cations and rare earth ions on the luminescence of MRE(MoO_4)_2:Eu~(3+) were investigated in detail. The experimental results show that the emission intensity was found to decrease with increasing the size of alkali cations or decreasing the size of rare earth ions. Under 393 nm light excitation, all compounds exhibited strong red emission at about 613 nm due to ~5D_0 → ~7F_2 transition of Eu~(3+). Compared with the commercially available red phosphor Y_2O_3:Eu~(3+), the emission intensity of the obtained phosphors is much stronger than that of Y_2O_3:Eu~(3+). Additionally, the excitation spectra of these phosphors implied that the MRE(MoO_4)_2:Eu~(3+) phosphors can absorb not only the emission of near UV-LED chips but also that of blue LED chips. The CIE chromaticity coordinates are close to the National Television Standard Committee (NTSC) standard CIE chromaticity coordinate values for red (0.67, 0.33). All the results indicate that these phosphors are promising red-emitting phosphors pumped by near-UV or blue light.