Surface layer in relaxor ferroelectric PZN- 4.5%PT single crystals

The origin of the extremely broad peak at the lower 2θ side of the main (002) rhombohedral x-ray peak in an unpoled (001)-cut Pb (Zn1/3 Nb2/3) 0.955 Ti0.045 O3 (PZN- 4.5%PT) single crystal has been examined. This peak, located at about 2θ∼43°-44°, was absent on fractured surfaces of the crystal but reappeared when the fractured surfaces were polished mechanically. High-resolution synchrotron x-ray mesh scans revealed that the as-polished surface was covered with a "deformed layer" of heavily stressed rhombohedral phase of monoclinic symmetry having its c axis lying perpendicular to the surface. This deformed phase can be structurally likened to one full of "incipient monoclinic nuclei/phases," which are microscopic in size and subject to intense compression in the plane of the surface. With a given polishing direction, this surface layer showed parallel domain patterns when viewed under the polarized light microscope. This surface layer could be largely eliminated by appropriate poling at 0.7-1.5 kV/mm at room temperature but became resistant to poling after annealing.