Barium titanate crystals are composed of numerous barium titanate cells. When the cubic barium titanate crystal is cooled to Curie point Tc, spontaneous polarization will begin and the transition from cubic to tetravalent phase will occur simultaneously. In the case of spontaneous polarization, one part of the adjacent cells may spontaneously polarized along a crystal axis of the original cubic cell, while the other part of the adjacent cells may spontaneously polarized along another crystal axis of the original cubic cell. Thus, when barium titanate is converted into tetragonal phase, small cells spontaneously polarized in different directions appear in the crystal, which are called electric domains. In other words, when the crystal is converted from parametric phase to ferroelectric phase by lowering the temperature, due to spontaneous polarization, the surface electrostatic interaction changes and the electric domain structure is generated.

The type of domain and the orientation of domain wall are mainly determined by the symmetry of crystal structure, but also satisfy the following two conditions: (1) the continuity of lattice deformation: the result of the formation of the domain, so that the crystal lattice produced by cutting along the domain wall is continuous and matched. Continuity of the spontaneous polarization component: the spontaneous polarization intensity of the two adjacent electric domains is equal in the direction perpendicular to the domain wall. Therefore, in the quadrangular barium titanate single crystal, the spontaneous polarization direction of adjacent electric domains can only intersect into 180° or 90°, that is, only 180° domains and 90° domains exist. In monoclinic barium titanate, due to the spontaneous polarization along the plane diagonal of the protocubic cell, there are 60° and 120° domains in addition to 180° and 90° domains. In addition to 180° domains, there are also 60° and 109° domains in the triclinal barium titanate.