Anisotropy of the real structure of triglycine sulphate domains

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Abstract
The method of decoration with anthraquinone has been used to study the electrically active real structure of the domains in triglycine sulphate (TGS) crystals doped with chromium, on the scale of optical microscopy. Decoration of crystal cleavage surfaces revealed regions of two types, both charged positively, since on both regions the anthraquinone crystals form uniaxial textures characteristic of the positive charge of the domains. These regions have sharp boundaries and their morphology and orientation correspond to those of the “ordinary” TGS domains. The detected domains differ from one another only in the orientation of the texture axes of the anthraquinone crystals, directed along the TGS and directions, respectively, i.e. in the electrical activity of the relevant crystallographic directions (also in several cases in the magnitude of the charge). On local regions of the crystal surfaces negative domains have also been detected, together with positive domains in which the crystallographic directions of the largest electrical activity are identical. The occurrence of domains of one and the same sign but differing in the electrical activity of different crystallographic directions is explained in terms of an anisotropic distribution of the electrically active impurity, in this case chromium, which may affect the charge sign of the domain as a whole and also may increase or decrease the electrical activity of one or the other crystallographic directions. It is suggested that the domains of one and the same sign, but differing from one another in the electrical activity of their crystallographic axes, may be present not only in TGS crystals but also in other ferroelectrics.