Physicochemical and Optical Characteristics of LiNbO3 Single-Crystals Doped with Boron

The chemical interaction in the Li 2 CO 3 –Nb 2 O 5 and Li 2 O–B 2 O 3 –Nb 2 O 5 systems and crystallization features of LiNbO 3 crystals from the melts containing boron impurity are considered. Raman spectra of LiNbO 3 :B crystals grown from a congruent melt containing ~0.55–1.24 mol % of B 2 O 3 are studied. There are noticeable changes in the entire Raman spectrum upon doping with boron, which indicates a change in alternation of the main cations and vacancies along the polar axis of the LiNbO 3 :B crystal and “perturbation” of oxygen octahedra. Moreover, expansion of oxygen octahedra is anisotropic with an increase in boron concentration in the melt. Boron, hardly entering the structure of the lithium niobate crystal, significantly changes the structure of the melt and thus has a significant effect on structure and physical characteristics of the LiNbO 3 :B crystals. The results obtained for the LiNbO 3 :B crystals are compared with those obtained for nominally pure stoichiometric (LiNbO 3stoich ) and congruent (LiNbO 3cong ) lithium niobate crystals.