Configurations of ferroelectric domains in bismuth- and zinc-modified Pb(Ni1/3Nb2/3)O-3-PbTiO3-PbZrO3 ceramics

Transmission electron microscopy was used to investigate the domain structu res of the (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)(0.2)(ZrsigmaTi1-sigma)(0.8)O-3 (0.30 less than or equal to sigma less than or equal to 0.70) ceramics, wh ich are located in the ferroelectric tetragonal and rhombohedral phase regi ons, and also near the morphotropic phase boundary (MPB). The results show that the lamellar twinning domains and the delta-fringe contrast are most f requently observed in the compositions located in the ferroelectrc tetragon al phase region. In the compositions near the MPB, a banded domain structur e similar to herringbone pattern is observed, which contains many parallel bands forming 90 degrees or 70 degrees angles whereas they are inconsistent with one another on both sides of the herringbone domain patterns. The mor phology of the herringbone domain structure observed in the bismuth- and zi nc-modified PNN-PZ-PT ceramics with composition near the MPB can be describ ed by a space-stacking succession of two crystallographically equivalent pl ates whereas made from different twin-related domains, with the same habit plane parallel to the (0.11)-type plane. In the compositions located in the rhombohedral phase region, the stripelike domains are observed, and a loca l random contrast representing short-range-ordered 'island'-typed polar clu sters or nanodomains is also found, which is attributed to the existence of the polar microregions with the dispersed nanometer-sized short-range-orde red domains in the rhombohedral matrix, because the free energy of the ense mble of the polar microregion is lowered, and the relative thermodynamic st ability is increased with increasing the content ratio of Zr to Ti. In addi tion, the wavy character in the thickness fringe is commonly observed at th e fringe of thin foil, which is due to continuous bending of the thin foil at various equivalent directions. (C) 1999 Klumer Academic Publishers.