XAFS STUDY OF THE ANTIFERROELECTRIC PHASE-TRANSITION IN PBZRO3

The temperature dependence of the local structure of PbZrO3 (PZ) was i nvestigated using XAFS analysis. This perovskite undergoes an antiferr oelectric (AFE) phase transition at about 500 K. XAFS of Pb L-III-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 t o the experimental data. The distortion parameters obtained at room te mperature are consistent with previous diffraction results. The Pb [1, 1,0] displacement remains almost constant at all temperatures. The ZrO 6 octahedron remains distorted at all temperatures but the exact disto rtion above Te cannot be determined. The oxygen AFE distortion and the [1,1,0] octahedral rotation decrease as temperature increases. At 824 K the oxygen distortions are at least 50% of their 298 K values. The p resence of structural distortions in the paraelectric phase of PZ indi cates that like in many other perovskites these distortions are not a result of soft lattice vibrational modes and that the AFE phase transi tion involves the ordering of local distortions.