Shapes of Growing Domains in Ferroelectric Triglycine Sulfate and Triglycine Selenate

In TGS and TGSe, shapes of the domains growing under electric field have been investigated on the basis of Nakamura's theory which offers the envelope constructed from elementary plane waves of growth. In the formula v = v ∞ exp (-δ/ E ) for the normal velocity v of sidewise wall motion under electric field E , the activation field δ has been assumed to be proportional to 3/2 powers of wall-energy density of σ'. The values of v in the various directions have been calculated with σ' obtained from the Zhirnov-type continuum theory. The domain shapes and their dependence on the applied field have been determined with the calculated values of v . The results satisfactorily explain the experimentally observed lenticular and elliptical shapes in TGS and the restricted lenticular, lenticular and elliptical shapes in TGSe. It has been shown that there exist critical fields for the classification of these kinds of shape.