THERMAL EVOLUTION OF BAZRO3 AND SRZRO3 PEROVSKITES FROM 4 K TO 773 K - AN EXAFS STUDY AT ZR-K EDGE

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 th e EXAFS and extracted photo-electron-wave phase-shift and scattering-a mplitude. This procedure allowed us to extract distances and Debye-Wal ler factors, taking into account photo-electron multiple scattering ef fects. For several atom shells, we fitted the evolution of the Debye-W aller factors as a function of temperature with Einstein or Debye mode ls. The characteristic temperatures obtained show that differences in dynamic behaviour between the two compounds are mainly due to Ba-Sr su bstitution and that differences in symmetry play a minor role.