The kinetics of barium precipitation at dislocations in NaCl monocrystals

The kinetics of barium precipitation at dislocations in NaCl monocrystals has been studied in thermally and mechanically treated NaCl + 4 ppm BaCl₂ samples by investigating the isothermic variation of ionic conductivity as a function of time. The course of precipitation which takes place at dislocations located at grain boundaries can be divided into three time regions characterized by diffusion of impurities to dislocation cores at grain boundaries, nucleation, formation of new grain boundaries, etc. At higher number of dislocations an interruption of the precipitation appears due to a local free energy of nucleation minimum at radiusr₀=6·92×10^–8 cm.