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Crystal Structures of SrBi2Ta2O9 and Sr0.8Bi2.2Ta2O9 Ferroelectric Materials
Published online by Cambridge University Press: 10 February 2011
Abstract
Structural and ferroelectric properties of stoichiometric SrBi2Ta2O9 and Sr-deficient-and-Bi-excess Sr0.8Bi2.2Ta2O9 bulk ceramics materials are studied. The ferroelectric Curie temperatures for SrBi2Ta2O9 and Sr0.8Bi2.2Ta2O9 are 300 and 400°C, respectively. Structure analysis by neutron powder diffraction reveals that Bi2O2 layer and TaO6 octahedra are considerably distorted and that atomic displacement along the a-axis causes ferroelectric spontaneous polarization. In Sro8Bi22Ta2O9, both Bi-substitution and cation-vacancies exist at the Sr-site. The calculated polarization of Sr0.8Bi2.2Ta2O9 is higher than that of the stoichiometric sample, which is consistent with observations of remanent polarization in thin-film capacitors. The Bi-substitution and the cation-vacancies at the Sr site enhance structural distortion in the TaO6 octahedron and lead to the higher Curie temperature and the higher ferroelectric spontaneous polarization.
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- Copyright © Materials Research Society 1999
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