Nanopowders Y1−yNdyV1−xCrxO4 with y=0 and 1; x=0, 0.1, 0.2 and 0.5 synthesized by a sol-gel process. Relationship between morphological characteristics and optical properties

Y1−yNdyV1−xCrxO4 nanopowders with y=0 and 0.1; x=0, 0.1, 0.2 and 0.5, have been synthetized by a sol-gel process followed by heating in an oxygen flow. This second treatment was done only in the case of samples containing chromium. The samples have been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural analysis revealed that when chromium was inserted at vanadium-sites in Y0.9Nd0.1VO4, the host retained the tetragonal symmetry corresponding to a zircon-type structure, attributed to the space group I41/amd. In addition, a loss of crystallinity was observed when chromium substitutes vanadium into the Y0.9Nd0.1VO4 host. The morphological studies revealed agglomerates of spherical particles whose size is increased with the Cr content and confirmed the composition of all synthetized samples. FTIR spectra of these samples exhibit a broadening and a slight shift of the bands around 830 cm−1 towards higher values of frequency when the chromium content increases. The effect of vanadium substitution by chromium on the optical properties was also evaluated by UV-vis absorption and photoluminescence (PL) spectroscopies. The broad UV band absorption is due to the presence of Cr5+. A decrease of PL emission is found when chromium substitutes vanadium in the YVO4 host.