DETERMINATION OF DISPLACEMENT VECTOR ON 180-DEGREES DOMAIN BOUNDARY AND POLARIZATION ARRANGEMENTS IN LEAD TITANATE CRYSTALS

180 degrees domain boundaries in flux-grown lead titanate single cryst als show intriguing domain boundary extreme fringe contrast using tran smission electron microscopy. Symmetrically distributed domain boundar ies with alternate contrast have been observed, indicating that opposi te displacement vectors exist one by one at boundaries, If appropriate reflection vectors were employed, an inclined domain boundary shows r eversed fringe contrast. An analysis based upon the two-beam dynamical theory and a rule similar to stacking-fault contrast analysis was emp loyed to predict the geometric configuration of a 180 degrees domain b oundary using the extreme fringe contrast (EFC) behavior. Appropriatel y choosing reflection Vectors and utilizing the EFC reversal, a displa cement vector as well as the polarization vector arrangement across a 180 degrees domain boundary can be unambiguously identified, Employing the information derived from diffraction patterns and a tilting exper iment across a nearby 90 degrees boundary, the whole polarization conf iguration can be uniquely determined.