X-ray absorption fine structure (XAFS) experiments were carried out on a series of ferroelectric materials $\mathrm{Pb}{\mathrm{Zr}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_3$ (PZT) $(x=0.40,0.47,0.49,0.55)$ to study the local structure around Ti and Zr atoms in each sample. Based on the fact that PZT has a single phase in the morphotropic phase boundary (MPB) from the x-ray diffraction measurements, both extended XAFS (EXAFS) and x-ray absorption near-edge structure results suggest that at $3\mathrm{K}$ the orientation of the Ti off-center displacement in these materials changes gradually from the [001] to [111] direction (in pseudocubic notation) as the Ti concentration $x$ decreases from 0.55 to 0.40. This is evidence for a continuous rotation of the local electrical polarization across the MPB region in PZT. The $\mathrm{Zr}K$-edge EXAFS data suggest that at low temperature, the $\mathrm{Zr}{\mathrm{O}}_6$ octahedra in PZT are less distorted than indicated from the average structure for all samples, though a small Zr displacement relative to the O atoms may exist. This possible small Zr displacement is also much less than that found in density functional theory calculations. The $\mathrm{Zr}{\mathrm{O}}_6$ local structure hardly changes with Ti concentration across the MPB region. Finally, the XAFS data also show that the sizes of the $\mathrm{Zr}{\mathrm{O}}_6$ octahedra are larger than that of the $\mathrm{Ti}{\mathrm{O}}_6$ octahedra which was also observed by experimental neutron pair distribution function analysis.

• Received 19 April 2004

DOI:https://doi.org/10.1103/PhysRevB.70.224102