Comparative study of Y0.9Er0.1V1−xPxO4 nanophosphors with x = 0, 0.1, 0.5, 0.9 and 1 prepared by sol-gel and hydrothermal processes

Y0.9Er0.1V1−xPxO4 nanophosphors with x = 0, 0.1, 0.5, 0.9 and 1 were synthesized by a sol-gel process and a low-temperature hydrothermal synthesis, in both cases under basic reaction conditions. The structural characteristics, particle morphology and luminescence properties of synthetized samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), micro-Raman and photoluminescence (PL) spectroscopies. XRD patterns of the samples obtained as single phases show diffraction maxima which can be indexed on the basis of a tetragonal symmetry of space group I41/amd with Z = 4, compatible with a zircon-type structure. TEM micrographs show spherical particles for samples prepared by sol-gel and more elongated particles for samples synthesized via hydrothermal. Phosphorus incorporation increases the average particle size and their elongation. A broadening of the Raman bands was observed when vanadium is substituted by phosphorus into the Y0.9Er0.1VO4 host, evidencing a structural distortion or non-equivalency vibrations of different vanadate groups. PL emission lines related to Er3+ intraionic transitions were observed in all investigated samples. The structural changes caused by phosphorus addition are responsible for a reduced energy transfer from the vanadate groups to the Er3+ ions, leading to a PL intensity decrease and a broadening of the rare earth luminescence emission bands.