Local structure in BaTi_1−xZr_xO₃ relaxors from neutron pair distribution function analysis

Claire Laulhé (1) , Francoise Hippert (1) , R. Bellissent (2, 3) , Annie Simon (4) , Gabriel Cuello (5)

1 LMGP - Laboratoire des matériaux et du génie physique
2 LLB - UMR 12 - Laboratoire Léon Brillouin
3 MMB - LLB - Matière molle et biophysique
4 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
5 ILL - Institut Laue-Langevin

The pair distribution functions (PDF) of BaTi_1−xZr_xO₃ (BTZ) relaxors (x=0.25,0.32,0.35), as well as those of the end members BaTiO₃ and BaZrO₃, were determined at 300 K from neutron powder scattering data. In the relaxors, the PDF provides direct evidence that the Ti and Zr atoms do not occupy the equivalent octahedral sites expected from the crystallographic cubic perovskite structure. It is shown that the TiO₆ and ZrO₆ octahedra in BTZ relaxors are instead similar to those observed in BaTiO₃ and BaZrO₃, respectively. In BaZrO₃, the Zr atoms lie at the center of regular oxygen octahedra, forming nonpolar ZrO₆ units. In the tetragonal ferroelectric phase of BaTiO₃, the distribution of Ti-O distances within TiO₆ octahedra is found compatible with a displacement of the Ti atoms in the [111]_p direction of the pseudocubic perovskite cell. We conclude that the local polarization in BTZ relaxors is mainly due to the displacements of the Ti atoms and that moreover the Ti displacements are very similar in BTZ relaxors and in the classical ferroelectric BaTiO₃.

Mots clés: Barium compounds; Crystal structure; Ferroelectric ceramics; Neutron diffraction; Relaxor ferroelectrics

Domaines: Matériaux; Science des matériaux [cond-mat.mtrl-sci]

Claire Laulhé, Francoise Hippert, R. Bellissent, Annie Simon, Gabriel Cuello. Local structure in BaTi_1−xZr_xO₃ relaxors from neutron pair distribution function analysis. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009, 79 (6), 064104 (10 p.). ⟨10.1103/PhysRevB.79.064104⟩. ⟨hal-00360257⟩