X-RAY TOPOGRAPHIC STUDY OF DOMAIN WALL MOVEMENT IN T. G. S.

During the X-Ray study of domains in ferroelectric T. G. S., we noticed random fluctuations of the X-Ray intensity diffracted by the sample. These fluctuations are shown to be related with domain boundaries oscillations due to a thermal gradient between the faces and the core of the sample, as the external temperature of the sample fluctuates. The understanding of this effect led us to attribute a special specific heat to the domain boundaries. The specific heat of a multidomain sample is therefore bigger than that of a monodomain sample. The increase of the number of domains and therefore of the walls in the vicinity of the Curie point allows us to give, with a semi-quantitative agreement, an interpretation for the difference between the specific heat increase observed experimentally (Taraskin [9] and Strukov [10]) and the increase predicted by the thermodynamical theory