Materials Chemistry and Physics, Vol.145, No.1-2, 18-26, 2014
Effect of synthesis conditions on the structural characteristics and luminescence properties of Y0.9Eu0.1V1-xCrxO4 (0 <= x <= 0.5) nanopowders
Y0.9Eu0.1V1-xCrxO4 (0 <= x <= 0.5) nanophosphors were synthesized under acid conditions (pH = 2) by a one-step sol-gel process followed by a thermal treatment at 843 K in oxygen flow. The obtained nanopowders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and by Raman and photoluminescence (PL) spectroscopies in a confocal microscope. The influence of pH on the structural characteristics and luminescence properties of the nanophospors was also assessed. XRD measurements reveal a progressive loss of crystallinity as chromium substitutes for vanadium in the samples. Such replacement induces a progressive broadening of the Raman peaks as the Cr content increases, evidencing a certain structural distortion involving different (VO4)(3-) groups due to the insertion of Cr5+ ions into the host. TEM images of the obtained nanopowders show changes in the particle shape and size of samples grown a different pH values. The addition of chromium hampers an effective energy transfer from the vanadate groups to the Eu3+ ions. This results in a strong decrease of the PL emission intensity corresponding to the intraionic transitions of this rare earth, irrespective of the synthesis conditions of the nanopowders. (C) 2014 Elsevier B.V. All rights reserved.