Effects of preparation method and pH variation on the structural characteristics and luminescence properties of Y0.9Er0.1VO4 and Y0.9Er0.1V0.9Cr0.1O4 nanopowders

Y0.9Er0.1VO4 and Y0.9Er0.1V0.9Cr0.1O4 nanopowders were synthesized by both sol-gel and hydrothermal synthesis. The effects of the preparation method, pH variation and replacement of V5+ by Cr5+ on the structure, particle shape and luminescence properties were investigated. A higher crystallinity is observed in the samples prepared in acid conditions by the sol-gel process, as compared with those synthesized in basic conditions. The opposite trend is found in those samples prepared by hydrothermal synthesis. Broadening of the Raman peaks was observed in spectra of the nanophosphors incorporating Cr, evidencing a certain distortion or non-equivalency of vibrations of (VO4)3− groups. TEM micrographs show changes in the particle shape related to the synthesis conditions. Photoluminescence (PL) related to Er3+ intraionic transitions was observed in all the samples investigated. An enhanced PL emission was observed in samples with a high degree of crystallinity. Magnetization measurements confirm the +5 oxidation state of Cr in the samples.