XAFS Study of the Antiferroelectric Phase Transition in PbZrO3

The temperature dependence of the local structure of PbZrO3 (PZ) was investigated using XAFS analysis. This perovskite undergoes an antiferroelectric (AFE) phase transition at about 500 K. XAFS of Pb LIII-edge and Zr K-edge in PZ were measured between 173 K and 824 K. The local structure was determined by fitting a parameterized theoretical XAFS to the experimental data. The distortion parameters obtained at room temperature are consistent with previous diffraction results. The Pb [1,1,0] displacement remains almost constant at all temperatures. The ZrO6 octahedron remains distorted at all temperatures but the exact distortion above Tc cannot be determined. The oxygen AFE distortion and the [1,1,0] octahedral rotation decrease as temperature increases. At 824K the oxygen distortions are at least 50% of their 298 K values. The presence of structural distortions in the paraelectric phase of PZ indicates that like in many other perovskites these distortions are not a result of soft lattice vibrational modes and that the AFE phase transition involves the ordering of local distortions