Patterns of ferroelectric domains in LiNbO₃ crystals characterized by X-ray topography

A complex pattern of opposite and antiparallel periodic poled domains in LiNbO₃ single crystals has been studied by X-ray topography. The antiparallel periodic poled domains appear directly at the growth interface during the growth in alternating crescent-shaped (CS) domains. The measured Li/Nb ratio is higher in the CS domains than in other zones. A model of the electric fields responsible for the observed configuration is proposed, connected to the role of the Li atom. Diffraction contrast associated with the different domain walls is examined and different kinds of dislocations associated with the ferroelectric domains are also studied, determining their geometrical characters.