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Descripción
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| Aurivillius in 1949(1), have the general formula (Bi2O2)2 (Am-1BmO3m+1)2- and are composed of pseudo-perovskite (Am-1BmO3m+1)2- blocks interleaved with bismuth oxide (Bi2O2)2+ layers along the c-axis; in this formula A represent a monovalent, divalent, or trivalent ion; B represents a tetravalent, pentavalent, or hexavalent ion, and m is the number of BO6 octahedra in the pseudo-perovskite block. The Bismuth titanate Bi4Ti3O12 (BIT) is ferroelectric, the Tc is about 675°C of pure BIT. Due to this high transition temperature, BIT ceramics are good candidates for high temperature piezoelectric applications. The principal problem is their low electrical resistivity. The electrical conductivity in BIT is highly anisotropic, with the maximum value in the same plane as the polarization. The spontaneous polarization determined in single crystals in the ab plane is ~50mC/cm2 and in the perpendicular direction is only 4 mC/cm2 (2). In this work BIT ceramics were processed by solid state synthesis from Bi2O3 and TiO2. The obtained had material different microstructure as a function of the sintering temperature due the anisotropic grain growth but their conductivy was similar became of the secondary phase Sillenite. In this work a study of the curves at hysteresis to different temperatures (RT up to 120°C) and with different mechanical stresses have been afforded. Non reported phenomenons were observed related to the temperature dependence of the ferroelectric response. An antiferroelectric type behavior was observed for grains with low plate size meanwhile a typical non symmetric ferroelectric curve ociates with microstructural defect appears for large plates with exaggerated growth. It was also found an ¿unblocking¿ field where these defects seem to be overcome and allowed to obtain ferroelectric response with Ps values of 5mC/cm2. | |
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Internacional
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Nombre congreso
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EC07-ELECTROCERAMICS |
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Tipo de participación
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960 |
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Lugar del congreso
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AVEIRO (PORTUGAL) |
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Revisores
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No |
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ISBN o ISSN
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DOI
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Fecha inicio congreso
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24/06/2007 |
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Fecha fin congreso
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26/06/2007 |
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