Electric domain twinning effects caused by phase transitions in ferroelectric are added to effects of structural, growing nonhomogeneity of crystals. It is clear, mechanical strains on domain boundaries are to be expressed in broadening of X-ray diffraction reflexes. Twinning effects, block structure and microdeformations of basic ferroelectric crystals (PbTiO$_{3}$, BaTiO$_{3}$, CdTiO$_{3}$, PbMg$_{0.3}$Nb$_{0.3}$O$_{3}$) were treated.
The crystals were investigated be Laue-, rotation methods and on diffractometer. Analysed regularities of twinning of different phases enabled us to identify reflexes at X-ray patterns due to belonging of them to different domains. The method of$\omega, 2\theta$ separate scanning was used for analyzing of block structure and microdeformations with respect to geometry of diffraction profiles. Annealing of crystals at temperatures above Curie's point leads to varying of real state parameters. Etching of crystals shows that structural imperfection of crystals in general are typical for surface layers with thickness of several microns.
The conducted investigations display that it is necessary to take real state parameters into account for correct determination of experimental structural amplitudes.