Preparação e caracterização de pós e filmes finos cerãmicos de titanato de chumbo e estrôncio obtidos por método químico.
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Date
2006-07-03Author
Leal, Sérgio Henrique Bezerra de Sousa
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ABSTRACT
In this work it is approached the preparation of ceramic powders and
thin films of strontium-doped lead titanate with concentration of strontium varing from
0 to 100% mol, using a chemical method of synthesis, polymeric precursor method
(Pechini). This method allows the sythesis in aqueous medium, in ambient
atmosphere, using reactants easily available. In this way, the synthesis condicions
were optimized in order to elimanate the formation of secondary phases. The
powders ceramic treated in different temperatures under ambient atmosphere was
studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), infrared
spectroscopy (FTIR), micro-Raman spectroscopy, scanning electron microscopy
(SEM) and transmission electron microscopy (TEM), that allowed the identification of
the crystalline phases, lattice parameters and crystallite size. A phase transition from
tetragonal to cubic was observed in this system as the stontium concentration
increases in the (Pb1-xSrx)TiO3. A pseudo-cubic phase was observed for x=0.5,
indicanting the complete solid solubility of the system. Thin films were obtained by
using spin coating of the polymeric solution on Pt/Ti/SiO2/Si substrates using a
rotation speed of 7600 rpm for 30 s and calcining at 600°C for 4 h. The effect of the
substituint ion in the microstructure and morphology of those films was discussed
through a systematic and detailed study using XRD, FTIR, micro-Raman
spectroscopy, optical microscopy and atomic force microscopy (AFM); where it was
verified that addition of strontium in the PT lattice resulted in decrease of avarage
grain size of those films.