Microstructural, magnetic and crystal field investigations of nanocrystalline Dy3+ doped zinc oxide

Dy3+ doped zinc oxide was prepared by co-precipitation method. The as-prepared samples were annealed at different temperatures to obtain the samples with different particle sizes. The crystallographic phases of all the samples were confirmed by X-ray diffraction (XRD) patterns. Rietveld analysis of the XRD pattern of the sample annealed at 80 degrees C showed that most of the Dy3+ ions were substituted in the Zn2+ site of the hexagonal ZnO lattice. But in case of samples annealed at higher temperatures, a fraction of Dy3+ ions comes out from the ZnO lattice and this fraction increases with the increase of annealing temperature. The sizes of nanoparticles and the lattice strains of all the samples were obtained from the Hall-Williamson plot. High resolution transmission electron microscopy showed that ZnO nanoparticles are more or less spherical. Magnetic susceptibilities (chi) of some selected samples measured in the temperature range of 300-14 K indicate that the samples are paramagnetic. Values of chi were successfully fitted by Curie-Weiss law. A good theoretical simulation of chi of the sample annealed at 80 degrees C has been achieved using the one-electron crystal field interaction of the Dy3+ ions with its diamagnetic neighbors in the hexagonal single crystal. (C) 2009 Elsevier Masson SAS. All rights reserved.