JOSE FERNANDO QUEIRUGA REY
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Capítulo IPEN-doc 16680 Phase transition in Basub(2)Insub(2)Osub(5) studied by in situ high temperature X-ray diffraction using synchrotron radiation2009 - REY, J.F.Q.; FERREIRA, F.F.; MUCCILLO, E.N.S.The order-disorder phase transition in Ba,In,Os high-temperature ionic conductor was systematically studied by in situ high-temperature X-ray diffraction using synchrotron radiation and electrical conductivity. Pure barium indate was prepared by solid state reactions at 1300°C. The room-temperature structural characterization showed a high degree of phase homogeneity in the prepared material. The reduction of the order-disorder phase transition temperature was verified by electrical conductivity and high-temperature X-ray diffraction. The observed features were explained based on Fourier-transform infrared spectroscopy results that revealed the presence of hydroxyl species in the crystal lattice. The increase of the intensity of few diffraction peaks near the phase transition temperature suggests the formation of a superstructure before the orthorhombic-to-tetragonal phase transition.Artigo IPEN-doc 13760 Primary particle size effect on phase transition in Basub(2)Insub(2)Osub(5)2008 - REY, J.F.Q.; FERREIRA, F.F.; MUCCILLO, E.N.S.The primary particle (or crystallite) size effect on the order–disorder phase transition temperature in Ba2In2O5 was investigated. Sintered specimens were prepared by solid state synthesis. Structural characterization performed by Raman spectroscopy shows that single-phase brownmillerite structure was obtained at room temperature for all prepared samples. In situ high-temperature X-ray diffraction experiments using Synchrotron radiation and electrical conductivity measurements reveal a decrease in the phase transition temperature with decreasing of the primary particle size. Lattice defects, mainly hydroxyls and nitrates, also influence the phase transition in Ba2In2O5.