João Pessoa, Brazil
João Pessoa, Brazil

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Alves M.C.F.,CNRS Chemistry Institute of Rennes | Marinho R.M.M.,LACOM INCTMN | Casali G.P.,LACOM INCTMN | Siu-Li M.,University of Sao Paulo | And 7 more authors.
Journal of Solid State Chemistry | Year: 2013

CaSnO3 and SrSnO3 alkaline earth stannate thin films were prepared by chemical solution deposition using the polymeric precursor method on various single crystal substrates (R- and C-sapphire and 100-SrTiO3) at different temperatures. The films were characterized by X-ray diffraction (θ-2θ, ω- and φ-scans), field emission scanning electron microscopy, atomic force microscopy, micro-Raman spectroscopy and photoluminescence. Epitaxial SrSnO3 and CaSnO 3 thin films were obtained on SrTiO3 with a high crystalline quality. The long-range symmetry promoted a short-range disorder which led to photoluminescence in the epitaxial films. In contrast, the films deposited on sapphire exhibited a random polycrystalline growth with no meaningful emission regardless of the substrate orientation. The network modifier (Ca or Sr) and the substrate (sapphire or SrTiO3) influenced the crystallization process and/or the microstructure. Higher is the tilts of the SnO6 octahedra, as in CaSnO3, higher is the crystallization temperature, which changed also the nucleation/grain growth process. © 2012 Elsevier Inc. All rights reserved.


Maul J.,LACOM INCTMN | Brito A.S.,LACOM INCTMN | De Oliveira A.L.M.,LACOM INCTMN | Lima S.J.G.,Federal University of Paraiba | And 4 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2011

Copper monoxide (CuO) was successfully obtained by microwave-assisted hydrothermal method, using different conditions-in a solution without base, in a solution alkalinized with NaOH or with NH4OH. The powders were analyzed by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, UV-Visible spectroscopy, and scanning electronic microscopy. XRD results showed that CuO was obtained with monoclinic structure and without secondary phases. Thermal analysis and infrared spectra indicated the presence of acetate groups on the powder surface. TG curves also showed a mass gain assigned to the Cu(I) oxidation indicating that a reduction possibly occurred during synthesis. The high and broad absorption band in the UV-Vis spectroscopy from 250 to 750 nm indicated the coexistence of Cu(II) and Cu(I), confirming the Cu(II) reduction, inside the CuO lattice. It was also possible to confirm the Cu(II) reduction by a displacement of the Me-O vibration bands observed in the IR spectra at around 500 cm-1. © 2011 Akadémiai Kiadó, Budapest, Hungary.

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