Effects of doping of Ca and Ba on the dislocation distribution in melt grown KCl crystals

Abstract

The effects of doping of Ca and Ba (-0.02 at yo) upon the dislocation distribution in melt grown KC1 crystals without cellular segregation were studied by an etch pit method in connection with the dispersion state of the dopants, which was examined by the dark field illumination. -(1) In the Ca-doped crystal, in which the dopants were distributed uniformly, the formation of subboundaries was completely suppressed and dislocations were distributed at random. (2) I n the Ba-doped crystal, however, the dopants were non-uniformly distributed and the dislocations tended t o form subboundaries. The dislocations within the subgrains were distributed in a non-uniform manner. (3) The dislocation density in the Ba doped crystal was higher than that of undoped or Ca-doped crystal.This was explained by the mechanism similar to the TILLER'S prediction.