Monocrystalline samples contained a cation impurity content of about 1ppm, and a dislocation density of between 104 and 105/cm2. The diffusivity was determined by using microtoming and activation analyses. At temperatures of between 374 and 505C, vacancy diffusion of 22Na through the lattice occurred and was governed by an activation energy of l.25eV. The existence of linear tails in the diffusion profiles was attributed to the occurrence of pipe diffusion down isolated dislocations. The activation energy for this process was 0.57eV (figure 28) and involved the excess cation vacancies in the charge cloud surrounding the dislocations. The radius of the latter charge cloud was estimated to be about 26nm.

Y.K.Ho, P.L.Pratt: Radiation Effects, 1983, 75[1-4], 183-92