Structural changes in CsI-based single crystals pulled from melt on seed


Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Lenin Ave., 310001 Kharkiv, Ukraine

Plastic deformation process occurring during the pulling of CsI, CsI(Na), CsI(Tl) and CsI(CO3) single crystals of 300 to 500 mm in diameter from the melt on the seed oriented along [001] has been studied. The plastic deformation kinetics has been established. First, the peripheral part of the crystal bends due to successive action of the primary and secondary sliding systems and then a deformation occurs in the cooled seed part caused by ever-increasing weight of the ingot itself. Examination of (100) and (010) plane sections in polarized light have shown that sliding strips, small-angle and large-angle boundaries are formed in the growing crystal due to various plastic deformation processes. The optimum seed orientation has been determined providing the production of large ingots with few structure defects.

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