Investigation of interaction between a dislocation and a Cl− or I− ion in NaBr single crystals

Strain rate cycling tests were carried out under superimposition of oscillatory stress for NaBr single crystals doped with Cl− or I−. The relationship between strain rate sensitivity (SRS) of flow stress and stress decrement Δτ due to superimposition of oscillatory stress is stair-like and consists of three regions, i.e. two plateau regions at low and high Δτ and a middle region where the SRS decreases with increasing Δτ. The stress τp at the first bending point between the first plateau region and the middle one, which is considered to be the effective stress due to Cl− or I−, decreases with increasing temperature. The difference (SRSp) between the SRS at the first and second plateau regions decreases with temperature. The SRSp is attributed to Cl− or I−. The interaction energies between a dislocation and a Cl− or I− are 0.40 or 0.47 eV in NaBr assuming that the force–distance profile is expressed by the Cottrell–Bilby relation. The force–distance profile is different from that for KCl:Br−.