Structural features, physicochemical, and optical characteristics of lithium niobate crystals grown from boron-doped melts

Chemical interactions in the Li$_{2}$O–B$_{2}$O$_{3}$–Nb$_{2}$O$_{5}$ system, as well as certain features of crystallization of LiNbO$_3$ crystals growing from melts containing nonmetal impurities, are considered. It is shown that boron changes the structure of the melt and has a significant impact on the structure and physical characteristics of LiNbO$_3$ : В crystals, practically not entering the lithium niobate structure. Notable changes and certain features were found in the Raman spectra of grown LiNbO$_3$ : В crystals, which indicates changing the sequence of the main cations and vacancies along a crystal polar axis and distortion of the oxygen octahedrons. Meanwhile, the distortion of the oxygen octahedrons is anisotropic. LiNbO$_3$ : В crystals have a higher structural homogeneity than congruent crystals, and are close in the number of NbLi defects to a crystal with a stoichiometric composition, differing from it by a substantially less photorefraction effect.