Potential red-emitting NaGd(MO4)2:R (M=W, Mo, R=Eu3+, Sm3+, Bi3+) phosphors for white light emitting diodes applications

NaGd(MO4)2:R (M=W, Mo, R=Eu3+, Sm3+, Bi3+) phosphors were synthesized by solid-state reaction. The structure and photoluminescence properties of the samples were characterized using X-ray powder diffraction and fluorescence spectrophotometry. The 5D0→7F2 transition of Eu3+, which led to a red emission of the phosphors, was dominantly observed in the photoluminescence spectra. The doped Bi3+ and Sm3+ efficiently sensitized the emission of Eu3+ and effectively extended and strengthened the absorption of near-UV light with wavelengths ranging from 395 to 405nm. In addition, energy transfers from Bi3+ to Eu3+ and from Sm3+ to Eu3+ occurred. The chromaticity coordinates of the obtained phosphors were close to the standard values of the National Television Standard Committee (x=0.670, y=0.330). The results suggest that NaGd(WO4)2−y(MoO4)y:Eu3+, Sm3+, Bi3+ is an efficient red-emitting phosphor for light-emitting diode applications.