Effects of x and R~(3+) on the luminescent properties of Eu~(3+) in nanocrystalline YV_xP_(1-x)O_4:Eu~(3+) and RVO_4:Eu~(3+) thin-film phosphors

摘要

Using inorganic oxides and salts instead of alkox-ides as the main starting materials, we prepared nanocrystalline YV_xP_(1-x)O_4:Eu~(3+) and RVO_4:Eu~(3+) (0 ≤ x ≤ 1; R = Y, La, Gd) thin-film phosphors by the Pechini sol-gel dip-coating process. The resulting films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and photolumines-cence excitation and emission spectra as well as luminescence decay. The results of XRD showed that a solid solution formed in the YV_xP_(1-x)O_4:Eu~(3+) film series from x = 0 to x = 1 with zircon structure. The same structure also held for the GdVO_4:Eu~(3+) film, but the LaVO_4:Eu~(3+) film crystallized with a different structure, monazite. AFM and SEM studies revealed that the phosphor films consisted of spherical particles ranging from 90 to 400 nm depending on the film compositions. With the increase of x values in YV_xP_(1-x)O_4:Eu~(3+) films, the integrated emission intensity and the red (~5D_0-~7F_2)-to-orange (~5D_0-~7F_1) intensity ratio of Eu~(3+) increase due to the increased energy-transfer probability from VO_4~(3-) to Eu~(3+) and the increased polarizability of the surrounding oxygen ions, respectively. The x values also have an influence on the decay behavior of Eu~(3+). The YVO_4:Eu~(3+) and GdVO_4:Eu~(3+) films showed very similar luminescence properties due to their same crystal structures. However, the LaVO_4:Eu~(3+) film exhibited a much different emission property from those of the YVO_4:Eu~(3+) and GdVO_4:Eu~(3+) films due to the structural effects.