A transmission electron microscopy study of the A-site disordered perovskite Na0.5Bi0.5TiO3

A transmission electron microscopy study of Na0.5Bi0.5TiO3 (NBT) crystals shows two types of ferroelectric domains characterized by interface boundaries lying in the {110}(C) and {100}(C) planes. A one-dimensional {100}(C) modulated texture is also observed locally. The electron diffraction study reveals the presence of (001)(T) tetragonal platelets a few cells thick within the R3c matrix. They develop within the three basal {100}(C) planes of the prototype phase and represent relics of the high-temperature tetragonal phase. The loss of symmetry compared to the average structure of NBT can thus clearly be attributed to the existence of these tetragonal platelets. The {0}(C) modulated texture corresponds to a modulation of strain induced by the coexistence of two types of octahedra tilting systems: a(-)a(-)a(-) for the rhombohedral matrix and a(0)a(0)c(+) for the tetragonal platelets. These (001)(T) Platelets indirectly intervene in the relaxation process classically encountered at about 230 degrees C, in marked contrast to the behaviour of Pb(Mg1/3Nb2/3)O-3. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.