Single crystals of nominally pure material, and of material doped with Mg2+, Ca2+, Sr2+ or Ba2+, were deformed by compression at 77 to 254K, during strain-rate cycling, in conjunction with ultrasonic oscillations. The data were analyzed in terms of the strain-rate sensitivity as a function of the stress decrement. The curve for material doped with divalent impurities exhibited 2 bending points and 2 plateau regions. It was proposed that the variation of the strain-rate sensitivity at the second plateau was due to a change in the forest dislocation density with shear strain. The forest dislocation density seemed to be increased, by divalent additions, during compression tests; due to jogs on the screw dislocations. It depended upon the concentration of impurities, and also upon the size of the impurity, at a given temperature. It was not possible to determine whether a change in the size of the impurity affected the mobile dislocation density.

Influence of Various Divalent Impurities on Dislocation Density in KCl:Mg2+, Ca2+, Sr2+ or Ba2+ Single Crystals. Y.Kohzuki: Journal of Materials Science, 2003, 38[5], 953-8