SPECIFIC FEATURES OF THE DEFECT STRUCTURE OF LiNbO3:B CRYSTALS

Specific features of the defect structure of nominally pure LiNbO3:B crystals were studied by the X-ray diffraction analysis. Nominally pure LiNbO3:B crystals were grown by Czochralski using the technology of the direct solid-phase doping of the congruent charge by orthoboric acid (H3BO3). The bonds lengths of Me-O in MeO6 clusters (Me-Li, Nb) determine the ferroelectric and nonlinear optical properties of the lithium niobate crystal. The values of these bonds in LiNbO3:B crystals differ significantly from the bonds lengths of the nominally pure congruent crystal LiNbO3cong. The differences in the bonds lengths are caused by a change in the properties of the boron-containing melt, technological parameters of the growth of LiNbO3:B crystals, and the localization of a trace amounts of boron in tetrahedral voids of the lithium niobate crystal structure. The results of the study of LiNbO3:B crystals were compared with those for nominally pure LiNbO3cong crystals and near-stoichiometric LiNbO3stoich (5,5 wt% K2O) ones.