An experimental investigation of factors influencing the electric strength of potassium chloride crystals

Experiments with single crystals are described, showing that the electric strength of potassium chloride is not significantly affected by the choice of electrode material. It is, however, considerably increased by treatments that introduce the structural defects, associated with residual strains, caused by plastic deformation. This does not seem to have been appreciated in the past. Structural defects of this sort can be created very easily, and great care is therefore required to obtain measurements of electric strength for strain-free crystals. It is speculated that this has not yet been done for crystals of any of the alkali halides. The electric strengths of strain-free crystals are the values suitable for comparison with existing theoretical predictions, and they may be as much as 50% less than those usually quoted for the alkali halides at room temperature.