Ferroelectric domains in pressureless-sintered barium titanate

Ferroelectric domains in pressureless-sintered BaTiO3 ceramics have been st udied using scanning and transmission electron microscopy. Both the 90 degr ees- and 180 degrees-type exhibiting the characteristic features of herring bones, square-nets, and "water-mark", respectively, are observed in polishe d sections. Most of the domains identified in thin foils are the convention al 90 degrees a-a type. Unconventional 90 degrees a-a domain boundaries lyi ng on {111} are also identified from the CO2-laser-sintered samples, but th ey have vanished after several minutes of electron beam irradiation. Both t he wedge-shape and overlapped "microtwin" domains exhibit the characteristi c delta-fringes. The displacement vector R of [101] is thought to have deri ved from a small lattice translation introduced by the rotation of the pola rization vector across the domain boundaries. Lattice-fringe images of the 90 degrees domain boundaries suggest that the lattice distortion has occurr ed to accommodate the strain generated by the c --> t-BaTiO3 phase transiti on. The strain thus induced is manifested by dot contrast appearing on the 90 degrees domain walls as revealed by transmission electron microscopy. Th e distribution of dots suggests that the strains are taken up inhomogeneous ly both along and across the domain boundaries by the crystal lattices. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd rights reser ved.