TRANSMISSION ELECTRON-MICROSCOPY STUDY OF DOMAIN BOUNDARIES IN PBTIO3

Domain boundary structures of flux-grown polydomain lead titanate single crystals have been studied using transmission electron microscopy. Inclined 90 degrees and 180 degrees domain boundaries show fringe contrast and were systematically analyzed under various diffraction conditions. Although 90 degrees domain boundaries are supposedly delta-type boundaries in BaTiO3, our results show that displacement plays an important role at boundaries and that the extreme fringe contrast (EFC) behavior of 90 degrees boundaries is of the (alpha,delta)-mixed type. In the present work, an analysis based upon the two-beam dynamic theory was conducted and a selection rule similar to stacking-fault contrast analysis was established to predict the geometric configuration of 180 degrees domain boundaries using EFC behavior. Examples are given and verified by tilting experiments and electron diffraction. The results are highly consistent and offer a convenient way to distinguish between 90 degrees and 180 degrees boundaries.