Navegando por Autor "Bagnato, Osmar Roberto"
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Artigo Structural and magnetic characterization of LaFe1-xAlxO3 (x=0 and 0.2) orthoferrites synthesized by gelatin method(Trans Tech Publications, 2017-07) Araújo, José Humberto de; Pimentel, Patrícia Mendonça; Dutra, J. L. S.; Lima, A. C.; Bagnato, Osmar Roberto; Costa, Asenete Frutuoso; Oliveira, Rosane Maria Pessoa BetanioThe rare-earth orthoferrites (LnFeO3) are promising materials for various applications, such as chemical sensors, cathode for SOFC, catalysts, among others. In general, these oxides are synthesized at temperatures higher than 700 °C. In this work, nanocrystalline LaFe1-xAlxO3 (x=0, x=0.2) powders were synthesized by a method that uses gelatin as organic precursor and heat treated at 400, 600 and 800 °C. The structural and magnetic characterization of powders was carried out by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Morphological analysis was performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns revealed the formation of orthoferrites single phase since 400°C. The powders exhibited weak ferromagnetic behavior at room temperature where the values of saturation magnetization, remanence and coercivity varied with the doping and heat treatment temperatureArtigo Synthesis and structural characterization of Sm-SrNickelates(David Publishing, 2012-06-25) Araújo, José Humberto de; Pimentel, Patrícia Mendonça; Oliveira, Rosane Maria Pessoa Betânio; Oliveira, Filipe Silva; Bagnato, Osmar Roberto; Melo, Dulce Maria de AraújoThe main purpose of this work was to obtain Sm-Sr nickelates nanoparticles with Ruddelsden-Popper type structuresobtained by a simple process such as gelatin synthesis. The powders were calcinated at 900 ºC and characterized by X-ray diffraction,thermogravimetric analysis, scanning electron microscopy and high-resolution transmission electron microscopy techniques. Theeffect of chemical substitution of the Sm3+ by Sr2+ ions on the structural properties of the powders was studied. The Rietveld’smethod was successfully applied for determination of the quantitative phase analysis of the powders and revealed that the main phaseof the powders for different strontium content is of Ruddelsden-Popper type structure. A symmetry change from orthorhombic totetragonal is observed as increasing strontium