Nepochatenko V. Basic regularities of forming a domain structure in ferro-elastics and multiaxial ferroelectrics

The thesis deals with the experimental and theoretical study of the process of forming a domain structure in ferroelastics and multiaxial ferroelectrics. The models of an anhistic and complex phase boundaries for the first order phase transition and the model of limiting phase boundary for the second order transition have been developed. Conditions of their forming, phase boundaries equations and pa-rameters of an intermediate phase have been defined. The concept of spontaneous turn of crystallographic axis of ferrophase relatively to paraphrase existence caused by atoms displacement and groups of atoms turns in spontaneous deformation and a method of its calculation have been suggested. Models of equi-librium domain walls which consist of intermediate layer of the induced phase are developed. The pa-rameters of an induced phase, elastic energy of a domain wall density have been determined. The method of defining functional relation between the lattice parameters under the condition of orientation corre-spondence of domains in a polydomain crystal has been suggested. The method enables to determine pos-sible structural changes and orientation disparity in domains which causes destruction of polydomain crystals.