Complex study of the structural and optical homogeneity of lithium niobate crystals.

Sidorov, N.; Palatnikov, M.; Yanichev, A.; Gabain, A.; Makarova, O.; Pikul', O.

Methods of Raman spectroscopy, laser conoscopy, optical microscopy, and electron spin resonance have been used to study the photorefractive properties and structural and optical homogeneity of the following lithium niobate (LiNbO) crystals: nominally pure crystals of congruent composition (LiNbO); LiNbO:Cu[0.015 wt %] crystals grown from a melt of congruent composition and nominally pure crystals of stoichiometric composition grown from a melt with 58.6 mol % LiO (LiNbO). A small deformation of optical indicatrix and regular microdomain structures of fractal type are revealed for the LiNbO:Cu[0.015 wt %]; the microdomain structures may be due to the nonuniform impurity incorporation into the structure. It is shown that oxygen octahedra in the LiNbO:Cu[0.015 wt %] crystal are deformed in comparison with the octahedra in LiNbO and LiNbO crystals and that the main and impurity cations are clusterized along the polar axis. It is established that the LiNbO:Cu[0.015 wt %] crystal exhibits photorefractive properties not only due to the presence of intrinsic defects with localized electrons, as in the case of LiNbO, but also due to the charge exchange in copper cations (Cu → Cu) under illumination.

LITHIUM niobate crystallography; METAL complexes; CRYSTAL structure; METAL crystals; RAMAN spectroscopy; OPTICAL properties of metals

Crystallography Reports, 2014, Vol 59, Issue 5, p724

1063-7745

Academic Journal

10.1134/S1063774514050162