Direct measurements of dislocation charges in Ca2+‐doped KC1 by using large electric fields

Abstract

Dislocation charges were measured for KCl single crystals doped with several concentrations of CaCl₂. The edge dislocations produced by scratching the surface moved under the sole action of an electric field larger than a certain critical value. The dislocation charges were calculated from this critical field and from the critical resolved shear stress for yielding. The sign of the dislocation charge was initially negative for all crystals. However, when the electric field was applied for a long time (1 min) with the electrodes in contact with the roughened surface of the crystal, the dislocation charge changed from negative to positive at the anode side and became even more negative at the cathode side. This effect is attributed to charge injection through the electrolytic action of the large electric field. The absolute values of both the initial and injected charges increased with increasing impurity concentration.