Structure of 180° Domain Walls in Ferroelectric Thiourea

Abstract

Antiparallel domain walls of ferroelectric thiourea have been observed on X-ray diffraction topographs. These domain walls are (001) planes with thicknesses less than 1 µm. Contrast of the images of the walls on the topographs depends on the kind of Bragg reflections used for the topographs. This dependence indicates that the structure of the domain walls is similar to the intermediate phase with modulated long period structures (phase II ′ and phase IV) observed between the high temperature paraelectric phase and low temperature ferroelectric phase. A Bragg reflection from the domain walls accompanies satellite reflections. The period of the modulated structure of the walls is estimated to be 300∼500 times the length of the c -axis of the ferroelectric phase.