Interactions between a dislocation and an impurity in Mg2+-doped (0.035mol% in the melt), Ca2+-doped (0.035 or 0.065mol% in the melt) and Ba2+-doped (0.050 or 0.065mol% in the melt) material were investigated by strain-rate cycling during Blaha-effect measurements at 77 to 254K. It was found that the Fleischer model, which took account of the Friedel relationship, seemed to be suitable for Ca2+- and Ba2+-doped material. It was not suitable for Mg2+-doped material. Values of Tc, ΔH(Tc) and ΔG0 were obtained for the specimens, where Tc was the critical temperature at which the effective stress was zero, and ΔH(Tc) and ΔG0 were the enthalpy and Gibbs free energy of activation for breakaway of the dislocation from an impurity, respectively. It was noted that ΔH(Tc) was almost the same for all of the specimens, except KCl:Mg2+. The value of ΔG0 increased with increasing divalent cation size. The tetragonality around the divalent ion-positive ion vacancy pair was estimated, on the basis of ΔG0, for each specimen.

Interaction between a Dislocation and Various Divalent Impurities in KCl Single Crystals for Fleischer’s Model taking Account of the Friedel Relation. Y.Kohzuki, T.Ohgaku:  Journal of Materials Science, 2001, 36[8], 2009-12