J. Phys. IV France 7 (1997) C2-1065-C2-1067
Thermal Evolution of BaZrO3 and SrZrO3 Perovskites from 4 K to 773 K : an EXAFS Study at Zr-K EdgeP.E. Petit1, F. Guyot1, 2 and F. Farges3
1 Laboratoire des Géomatériaux IPGP, URA 734 du CNRS, 4 place Jussieu, 75252 Paris cedex 05, France
2 Laboratoire de Minéralogie-Cristallographie, and IPGP, URA 09 du CNRS, 4 place Jussieu, 75252 Paris cedex 05, France
3 LPMG, IFI, UMLV, URA 734 du CNRS, 2 rue de la butte verte, 93166 Noisy le Grand cedex, France
In order to better understand the lattice dynamics of perovskites, we have performed temperature-dependent XAS measurements at Zr-K edge on BaZrO3 and SrZrO3. At ambient temperature, BaZrO3 is cubic, and SrZrO3 orthorhombic. For both compounds, using the FEFF6 code, we modeled the EXAFS and extracted photo-electron-wave phase-shift and scattering amplitude. This procedure allowed us to extract distances and Debye-Waller factors, taking into account photo-electron multiple scattering effects. For several atom shells, we fitted the evolution of the Debye-Waller factors as a function of temperature with Einstein or Debye models. The characteristic temperatures obtained show that differences in dynamic behaviour between the two compounds are mainly due to Ba-Sr substitution and that differences in symmetry play a minor role.
© EDP Sciences 1997