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24 July 1998 Elastic and dielectric forces acting on the 90-deg twin boundary in a ferroelectric crystal
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In the frame of the continuum theory of lattice defects the 90 degree(s) twin boundary in ferroelectrics is treated as a source of inhomogeneity and internal distortion in both elastic and electric field. The respective elastic and dielectric components of thermodynamic forces acting on the boundary are determined from the balance of total electro- elastic energy of the body and its loading system. Finite element model of the basic side-wise movement of a single twin boundary in barium titanate crystal under electrical and/or mechanical loading has been used in evaluating the thermodynamic forces and predicting the trends in the twin boundary movement. The effect of the 180 degree(s) substructure has been incorporated in the model by means of `softening' the dielectric distortion. The results are compared with known experimental observations. It is shown that the magnitude of the dielectric force on distortion strongly depends on 180 degree(s) substructure in the crystal. The movement of the 90 degree(s) twin boundary, therefore, cannot be predicted unambiguously because it depends on the degree of unequilibrium in substructure and on its rigidity. Several loading cases by aiding and opposing electric voltage or mechanical surface tractions are considered and the case of combined loading is investigated.
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Serguei Kovalev and Mototsugu Sakai "Elastic and dielectric forces acting on the 90-deg twin boundary in a ferroelectric crystal", Proc. SPIE 3323, Smart Structures and Materials 1998: Mathematics and Control in Smart Structures, (24 July 1998);

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