Luminescent properties of R2(MoO4)3:Eu3+ (R=La, Y, Gd) phosphors prepared by sol–gel process

A series of red phosphors R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) have been synthesized by sol–gel method. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction (XRD) and thermogravimetry–differential thermal analysis (TG–DTA), and the properties of these resulting phosphors have also been characterized by photoluminescence (PL) spectra and reflectance spectra. Field emission scanning electron microscopy (FE-SEM) was also used to characterize the shape and the size of the samples. The results of TG–DTA and XRD indicated that all of the R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) phosphors crystallized completely at 650 °C. Y0.8Eu1.2(MoO4)3 and Gd0.8Eu1.2(MoO4)3 have two structures, monoclinic and orthorhombic, while La0.8Eu1.2(MoO4)3 only adopts monoclinic structure. The luminescent properties of phosphors R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) are dependent on their structures to some extent. The orthorhombic Y0.8Eu1.2(MoO4)3 and Gd0.8Eu1.2(MoO4)3 phosphors show very similar luminescent properties, which differ from those of phosphors with monoclinic structure. For all of R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) phosphors, intense red emission is obtained by exciting at ∼394 and ∼465 nm which are owing to the sharp 7F0→5L6 and 7F0→5D2 lines of Eu3+. Two strongest lines at 394 and 465 nm in excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based LEDs, so they could be used as red components for white light-emitting diodes.