Navegando por Autor "Zampieri, M."
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Artigo Experimental and theoretical correlation of very intense visible green photoluminescence in BaZrO3 powders(American Institute of Physics, 2008) Cavalcante, L. S.; Zampieri, M.; Espinosa, J. W. M.; Pizani, Paulo Sérgio; Paskocimas, Carlos Alberto; Sambrano, Julio Ricardo; Silva, Elson Longo da; Varela, José A.; Simões, M. L.; Longo, V. M.Very intense visible green photoluminescence PL was observed at room temperature in structurally ordered-disordered BaZrO3 powders. Ab initio calculations, ultraviolet-visible absorption spectroscopy, electron paramagnetic resonance, and PL were performed. Theoretical and experimental results showed that local defects in the cubic structure caused by ZrO5 ·VO z complex clusters, where VO z =VO x , VO • , and VO ••, play an important role in the formation of hole-electron pairs, giving rise to a charge gradient in the structure which is responsible for PL emissionArtigo Structural analysis of Ti and Pb citrate using NMR and FT-Raman signals and quantum mechanics simulations(Springer, 2006-01-02) Zampieri, M.; Lazaro, S. R.; Paskocimas, Carlos Alberto; Ferreira, A. G.; Silva, Elson Longo da; Varela, José A.Titanium citrate and lead and titanium citrate were prepared by polymeric precursor method in aqueous solution. This citrate was analyzed by 1H, 13C NMR and gHMBC–NMR (Hetero-nuclear multiple-bond correlation) to investigate the formation of the citrate complexs and influence of the Pb2+ ion in this complex. These complexs were characterized by interaction between Ti4+ ion and citric acid carboxyls. Quantum mechanic simulations in level ab initio were used to study the electronic structure and natural charges (NBO) to both the complexs. Such techniques indicated the formation of an octahedral complex with an arrangement similar to Ti atom in the crystalline structure of the PbTiO3. A study using the technique FT-Raman made possible the confirmation of the interaction among the Ti4+ and Pb2+ ions with the citric acid carboxyls