Effects of Impurities on the Charged Dislocations in Sodium Chloride Single Crystals

Abstract

The dependence of the electric charge of the edge dislocations in sodium chloride on impurity atoms was investigated at room temperature. It was found that the edge dislocations are negatively charged when the crystal contains positive divalent impurities (Mg⁺⁺, Ca⁺⁺) and are positively charged when the crystal contains negative divalent impurity (S⁻⁻).
Measurements have been done on the decay of the electric potential on the surfaces of the crystal when the crystal is suffering a cyclic plastic bending of 120 c/s of a finite amplitude. The electric potential on the surfaces decays through two stages and the decay depends on the kind and the concentration of the divalent impurity atoms contained in the crystal. This decay aspect was discussed in terms of the dislocation multiplication and the decrease of the electric charge of the dislocations during the cyclic plastic deformation.