Navegando por Autor "Abreu, Maria Fernanda C."
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Artigo Effect of process parameters on photophysical properties and barium molybdate phosphors characteristics(Elsevier, 2014) Abreu, Maria Fernanda C.; Motta, Fabiana Villela da; Lima, Renata Cibely Freire de; Li, Maximo S.; Longo, Elson; Marques, Ana Paula de A.Barium molybdate particles (BaMoO4) with uniform shapes have applications in various fields such as phosphors, optical fibers, scintillators, magnets and catalysts. In this study, two synthesis methods (microwave-assisted hydrothermal (MAH) and Complex Polymerization (CP)) were used to prepare BaMoO4 particles. The effect of the applied synthesis methodology and experimental parameters on the morphology, particle size, sample uniformity and optical properties of the BaMoO4 were studied. Scheelite-type single crystalline structures of BaMoO4 were identified by X-ray diffraction (XRD) as well as Raman and Fourier transform infrared spectroscopy (FTIR). Octahedral morphologies were characterized by field-emission scanning electron microscopy (FE-SEM). Photoluminescence (PL) spectra of the samples exhibited different emission properties which indicates a relationship with surface defect states (shallow and deep level defects) where interfaces populate additional levels in the band gap. Electronic order-disorder at short- and intermediate-ranges is generated by utilizing the synthesis method and can be modified by applied experimental parameters. If the particle size and morphology are controlled, deep and shallow defects can be controlled, and PL properties can be modified accordingly with the optical properties desiredArtigo Preparation and photoluminescence characteristics of In(OH)3:xTb3+ obtained by Microwave-Assisted Hydrothermal method(Elsevier, 2013-03-15) Motta, Fabiana Villela da; Marques, Ana Paula de Azevedo; Li, Maximo Siu; Abreu, Maria Fernanda C.; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Souza, Ricardo Pires de; Varela, José A.; Silva, Elson Longo daCrystalline terbium-doped indium hydroxide structures were prepared by a rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at a low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of terbium-doped indium hydroxide (In(OH)3:xTb3+) samples under excitation (350.7 nm) presented broad band emission referent to the indium hydroxide matrix and 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3 terbium transitions at 495, 550, 590 and 627 nm, respectively. Relative intensities of the Tb3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol%, of Tb3+, but the luminescence is drastically quenched for the In(OH)3 matrix