Local structure in BaTi<sub>1−<i>x</i></sub>Zr<sub><i>x</i></sub>O<sub>3</sub> relaxors from neutron pair distribution function analysis
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en
Article de revue
Ce document a été publié dans
Physical Review B: Condensed Matter and Materials Physics (1998-2015). 2009-02-09, vol. 79, n° 6, p. 064104 (10 p.)
American Physical Society
Résumé en anglais
The<sup> </sup>pair distribution functions (PDF) of BaTi<sub>1−<i>x</i></sub>Zr<sub><i>x</i></sub>O<sub>3</sub> (BTZ) relaxors (<i>x</i>=0.25,0.32,0.35), as<sup> </sup>well as those of the end members BaTiO<sub>3</sub> and ...Lire la suite >
The<sup> </sup>pair distribution functions (PDF) of BaTi<sub>1−<i>x</i></sub>Zr<sub><i>x</i></sub>O<sub>3</sub> (BTZ) relaxors (<i>x</i>=0.25,0.32,0.35), as<sup> </sup>well as those of the end members BaTiO<sub>3</sub> and BaZrO<sub>3</sub>,<sup> </sup>were determined at 300 K from neutron powder scattering data.<sup> </sup>In the relaxors, the PDF provides direct evidence that the<sup> </sup>Ti and Zr atoms do not occupy the equivalent octahedral<sup> </sup>sites expected from the crystallographic cubic perovskite structure. It is<sup> </sup>shown that the TiO<sub>6</sub> and ZrO<sub>6</sub> octahedra in BTZ relaxors<sup> </sup>are instead similar to those observed in BaTiO<sub>3</sub> and BaZrO<sub>3</sub>,<sup> </sup>respectively. In BaZrO<sub>3</sub>, the Zr atoms lie at the center<sup> </sup>of regular oxygen octahedra, forming nonpolar ZrO<sub>6</sub> units. In the<sup> </sup>tetragonal ferroelectric phase of BaTiO<sub>3</sub>, the distribution of Ti-O distances<sup> </sup>within TiO<sub>6</sub> octahedra is found compatible with a displacement of<sup> </sup>the Ti atoms in the [111]<sub><i>p</i></sub> direction of the pseudocubic<sup> </sup>perovskite cell. We conclude that the local polarization in BTZ<sup> </sup>relaxors is mainly due to the displacements of the Ti<sup> </sup>atoms and that moreover the Ti displacements are very similar<sup> </sup>in BTZ relaxors and in the classical ferroelectric BaTiO<sub>3</sub>.< Réduire
Mots clés en anglais
Barium compounds
Crystal structure
Ferroelectric ceramics
Neutron diffraction
Relaxor ferroelectrics
Origine
Importé de halUnités de recherche