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Abstract: In lithium niobate single crystals, striae of planar defect lying on nearly ( ) were formed during the Czochralski growth. A stria was a small angle tilt boundary including a set of undissociated edge dislocations with the Burgers vector of a/3[ ], arranged at similar intervals of about . The dislocations extended perpendicular to the growth interface, leaving from the basal plane, presumably for the reduction of their strain energy during the growth. The formation process was discussed in terms of thermal stress at the growth interface during crystallization. [Copyright &y& Elsevier]

Abstract: Defects related to oxygen and other impurities in piezoelectric langasite (La3Ga5SiO14; LGS) single crystals grown by the vertical Bridgman (VB) method was investigated. The resistivity of an LGS crystal grown in an Ar atmosphere was about one-order higher than that grown in air. However, after annealing in air it decreased to the same level as that of LGS crystal grown in air. The results of optical transmission spectra showed a broad adsorption peak around 500nm, corresponding to 2.5eV of energy level, in LGS crystals grown in air and grown in an Ar atmosphere. Since VB-grown LGS crystal was p-type, excess interstitial oxygen atoms, not oxygen vacancies, operate as an acceptor in the VB-LGS crystal. [Copyright &y& Elsevier]