Temperature Dependence of the Stress Due to Additives in KCl Single Crystals

The influence of the state of additive cations on the various deformation characteristics was studied for KCl:Sr2+ single crystal at room temperature. This result gives the heat treatment suitable for the crystal immediately before deformation tests, such as compression and tension. Four kinds of single crystals (KCl: Mg2+, Ca2+, Sr2+ or Ba2+) were plastically deformed by compression at 77 to room temperature. The plasticity of the crystal depends on dislocation motion from a microscopic viewpoint. When a dislocation breaks away from the defect around the additive cation with the help of thermal activation on the slip plane in the crystal, the variation of effective stress with the temperature was investigated by the combination method of strain-rate cycling tests and ultrasonic oscillations. Furthermore, the critical temperature Tc at which the effective stress due to the additives is zero was estimated for each of the crystals. As a result, Tc value tends to be larger with the divalent cationic size.