The sign of charged dislocations in NaCl

Abstract

NaCl crystals were plastically bent at room temperature, under controlled conditions, and then vibrated in push—pull deformation at low stress amplitudes. The potentials developed on surface electrodes during vibration were investigated. It has been possible to distinguish between charge effects due to edge and to screw dislocations. Results indicate that edge dislocations in a nominally pure crystal bear a negative charge, whereas those in an oxide-doped crystal bear a positive charge; these conclusions are complementary to those of Rueda and Dekeyser who used an indentation technique. No charge effects due to screw dislocations were detectable. Results are compared qualitatively with the theory of Eshelby et al. and found to be in agreement.