Síntese e caracterização de nanopartículas de CeO2 dopadas com metais de transição : estudo das propriedades estruturais e magnéticas

• Autor(a) principal: Barbosa, Cristiane Cupertino Santos
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/8040
• topic: Física; Óxido de cério (CeO2); Nanopartículas; Óxido semicondutor magnético diluído (OSMD); Resultados de difração de raios X (DRX); UV-vis; Magnetização; Nanoparticles; Oxide-diluted magnetic semiconductor (O-DMS); X-ray diffraction (XRD); UV-vis; Magnetization.; CIENCIAS EXATAS E DA TERRA::FISICA

In this work we study the structural and magnetic properties of pure and TM-doped CeO2 nanoparticles (TM: Mn, Cr, Co and Fe) obtained by the co-precipitation and hydrothermal methods. X-ray diffraction (XRD) results allied to the Rietveld refinement method indicate that all samples present single-phase with structure isomorphous to the CeO2. Average crystallites size was determined using the full width at half maximum from XRD patterns and their sizes were from of 7 to 13 nm. Transmission electron microscopy (TEM) images 10% doped samples show the presence of particles with spherical-like morphology and average sizes in good agreement with the estimated by XRD. From ultraviolet–Visible (UV–Vis) spectroscopy absorption measurements we estimated the optoelectronic gap of the samples, which vary between 2.87 and 3.44 eV. Analyses from magnetization curves as a function of temperature (MvsT) using Curie-Weiss law show that the number of paramagnetic ions per molecule (n) increases with the increasing of the Mn concentration. Already for 10% doped samples with different ions the (n) obeys the following order Mn ˂ Fe ˂ Cr ˂ Co for samples obtained by co-precipitation and Co ˂ Cr ˂ Mn ˂ Fe for the samples obtained by hydrothermal synthesis. Magnetization curves as a function of the magnetic field (MvsH) show that the the systems present a weak ferromagnetic behavior at 5K and paramagnetic at temperature higher than 200 K.