V.I.Goriletsky
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.