Structural disorder and optical properties of congruent lithium niobate crystals doped with zink and boron

From the concentration dependence of the widths and intensities of Raman lines and from the patterns of photoinduced light scattering, it is found that the mechanism of incorporation of Zn2+ cations into the LiNbO3 crystal structure changes with increasing concentration of zinc in the melt, which leads to an abrupt anisotropic expansion of oxygen octahedra along the polar axis. In this case, the number of kinks in the concentration dependence of linewidths (5) considerably exceeds the number of concentration threshold (2) known from the literature. It is shown that B3+ ions almost do not enter the cationic sublattice of the LiNbO3 crystal but changes the melt structure, so that the LiNbO3:B crystal is characterized by a high structural and optical homogeneity and a low photorefractive effect.