Potential red-emitting NaGd(MO4)2:R (M=W,Mo, R=Eu,Sm, Bi) 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 405 nm. 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.