On the Gyulai-Hartly Effect in Single Crystals of Potassium Iodide at Temperatures between 77° and 297°K

The increase of the dark current caused by plastic deformation in potassium iodide crystals has been measured at temperatures between 77° and 297°K. The Gyulai-Hartly effect was not found to be dependent on temperature in this range. The maximum current induced by the deformation decreased in repeated deformation experiments, as has also been observed at higher temperatures. At 77°K a charge flow in the opposite direction to the Gyulai-Hartly effect was found when the load was removed. On further deformation, a charge flow in the above direction was observed, instead of the expected Gyulai-Hartly effect. As a result of successive deformation experiments, saturation currents associated with work hardening were measured. Potassium iodide crystals containing R′ centers did not show any Gyulai-Hartly effect at 297°K.