STUDY OF IMPERFECTIONS AND STRUCTURE IN NONLINEAR-OPTICAL CRYSTALS OFBETA-BAB2O4

Imperfections in single crystals of the low-temperature form of barium boric oxide grown by the flux method were observed and studied by X-r ay diffraction topography. The main structural defects are dislocation s with severe pinning at both ends and impurity decoration, impurities , helical dislocations, dislocation loops, inclusions, electric domain s, crystal boundaries etc. The possible origins of defects together wi th their contrast are discussed briefly from the structural point of v iew.