Photoluminescence properties of M3+ (M3+=Bi3+, Sm3+) activated Na5Eu(WO4)4 red-emitting phosphors for white LEDs

The red phosphor Na5Eu(WO4)4 activated with trivalent M3+ (M3+ = Bi3+, Sm3+) ions were prepared through the solid state reaction technique. The properties of structure, morphology, photoluminescence were characterized systematically. The lattice parameters were refined by Rietveld method. The emission spectra, excitation spectra, and decay curves were employed to study the luminescent behaviors. Both of Bi3+ and Sm3+ doping could increase the red-emitting intensity and corresponding quantum efficiency (QE) of Na5Eu(WO4)4 host. Furthermore, the color rendering index of the commercial yellow phosphor YAG:Ce3+ was increased from 44.5 to 50.8 and 50.2 by mixed with Na5Eu0.8Bi0.2(WO4)4 and Na5Eu0.96Sm0.04(WO4)4 phosphors under 465 nm excitation, respectively. The CIE chromaticity coordinates of these phosphors are close to the standard value for red. Herein, the present materials are promising candidates as red phosphors for white light emitting diodes with near-UV/blue GaN-based chips.