Browsing by Author "Padilla-Campos, L."

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    Chemical and structural analysis related to defects in nanocrystalline Ba1-xSrxTiO3 grown via hydrothermal sol-gel
    (2014) Fuentes, S.; Cespedes, F.; Padilla-Campos, L.; Diaz-Droguett, D. E.
    The chemical and structural properties of Ba1-xSrxTiO3 (BST, x=0-1) nanoparticles synthesised via sol-gel-hydrothermal were analysed. Two types of salts of Ba (BaCl2 and Ba(OH)(2)) and Sr (SrCl2 and Sr(OH)(2)) as starting reactants were used to compare two synthesis methods. Chemical characterisation and oxidation states were obtained using X-ray photoelectron spectroscopy. Structural information was acquired by Raman spectroscopy, and calculations to obtain theoretical Raman spectra associated with the different formed phases of BST were performed for comparison. The results were consistent with the presence of oxygen vacancies in all of the compounds synthesised, but the use of hydroxide salts introduced a minor concentration of oxygen vacancies into the BST compounds. In addition, the presence of oxygen vacancies produced an increase of the intensity of first-order modes of vibration and a minor oxidation state of the Ti atom in the structure. Finally, the oxygen vacancies produced a distortion of the structure, inducing the existence of the non-perovskite phase. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    Influence of reactant type on the Sr incorporation grade and structural characteristics of Ba1-xSrxTiO3 (x=0-1) grown by sol-gel-hydrothermal synthesis
    (2013) Fuentes, S.; Chavez, E.; Padilla-Campos, L.; Diaz-Droguett, D. E.
    The influence of barium and strontium starting reactants used in different mole ratios, BaCl2 and Ba(OH)(2), SrCl2 and Sr(OH)2(,) on the chemical and structural properties of Ba1-xSrxTiO3 (x=0-1) (BST) nanoparticles prepared via sol gel-hydrothermal synthesis in an oxygen atmosphere is discussed. The effect of the type of reactant on the relative amount of Sr incorporated in BST compound was also analysed. The synthesised BST nanoparticles showed differences in their structural and chemical characteristics, which were attributed to the presence of Cl- or OH- anions during the synthesis of the compound. The structure, morphology and oxidation state of the samples were studied by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. In addition, theoretical calculations using cluster models were carried out to understand the possible phases formed of BST, the effect of the Sr incorporation and the possible presence of oxygen vacancies inside the BST structure. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.