Synthesis and luminescent properties of high brightness MLa(WO4)2:Eu3+ (M=Li, Na, K) and NaRE(WO4)2:Eu3+ (RE=Gd, Y, Lu) red phosphors

Eu3+-activated double tungstates phosphors MLa(WO4)2 (M=Li, Na, K) and NaRE(WO4)2 (RE=Gd, Y, Lu) have been successfully prepared via the conventional solid-state reaction method. The effects of alkali ions and rare earth ions on the luminescence of MLa(WO4)2:Eu3+ and NaRE(WO4)2:Eu3+ were investigated. In MLa(WO4)2:Eu3+ system the emission intensity was found to decrease with increasing the size of alkali ions, and in NaRE(WO4)2:Eu3+ system the emission intensity can be ordered as follows: Lu>Y>Gd. Moreover, under 393 nm light excitation all compounds exhibited strong luminescence of 5D0→7F2 at 615 nm. The excitation spectra implied that these phosphors can absorb not only the emission of near UV-LED chips but also that of blue LED chips. All the results indicate that these phosphors are promising red-emitting phosphors pumped by near-UV or blue light.