Aplicação do método de Rietveld `a determinação da distribuição de cátions em ferritas de cobalto e de magnésio
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2010
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Universidade Federal de Goiás
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We present cobalt ferrites (CoxFe3−xO4) and magnesium ferrites (MgxFe3−xO4) nanoparticles synthesized by combustion reaction and coprecipitation. The study by powder diffraction, with CuK (λ =1,5406 °A) radiation, allowed us a phase qualitative analysis, determine the lattice parameter and the crystallites average size. How Co and Fe scattering factor are close to this radiation, we also used synchrotron radiation with energies 7.038 KeV, 7.112 KeV, 7.122 KeV and 7.718 KeV. With Rietveld refinement we made a phase quantitative analysis, we found Fe2O3, MgO and MgO2 as additional phases for MgxFe3−xO4 and we found CoO and Co3O4 as additional phases for Co1,2Fe1,8O4, all obtained by combustion method. The distribution determined for all ferrites nanoparticles characterized a cubic spinel type mixed, i.e. divalent ions were found in both sites. With experiments on a vibrating sample magnetometer (VSM) we compare the saturation magnetization of our samples with the magnetization of the unit cell calculated from the distribution determined experimentally.
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NUNES, Rafael Silva. Aplicação do método de Rietveld `a determinação da distribuição de cátions em ferritas de cobalto e de magnésio. 2010. 107 f. Dissertação (Mestrado em Física) - Universidade Federal de Goiás, Goiânia, 2010.