For the experimental research of process of formation of domain structure in lithium niobate with gradient of concentration the focused crystal plate of 0.4 mm (a so-called z-cut, i.e. the allocated axis of the crystal is perpendicular plate planes) has been used in the thickness. Put during crystal pulling up time the gradient of structure of the plate of lithium niobate along an axis x was close to linear and changed at level of 2% (from $R=0.94$ to 0.96). Crystal repolarization was made by the appendix to a thin plate of a high voltage. Peak value made 7 kV. Reflection of domain formation processes in electric field time change of values of the field necessary for repolarization is. From experimental data, follows that formation of domain structure in the crystal lithium niobate with gradient of concentration occurs practically at one value of the polarizing pressure brought to a crystal plate. And, the current starts to proceed through a plate at excess of level of pressure 6.5 kV that makes 16.5 kV/mm. Certainly, the given value is the integrated parameter characterizing all plate of lithium niobate entirely. However the strongly pronounced beginning of formation of domains testifies, as well as it was supposed about insignificance of influence of a gradient of structure of a plate in the borders specified above under condition of replacement of defects "niobium in lithium site" ions non-photorefractive impurity.

В статье приводится экспериментальное исследование процесса формирования регулярной доменной структуры в градиентном ниобате лития. Указываются условия формирования доменной структуры в градиентом ниобате лития при использовании активированной ионами нефоторефрактивных примесей кристаллической пластины.