A thin-layer method was used to study the diffusion, and final-concentration versus distance profiles were measured by using an optical absorption method. The Arrhenius plot exhibited 2 straight segments. The results for low temperatures (table 271) could be described by:

D (cm2/s) = 10.0 exp[-1.00(eV)/kT]

The results for high temperatures could be described by:

D (cm2/s) = 0.026 exp[-0.652(eV)/kT]

The diffusion coefficient for Cu exceeded the self-diffusion coefficient for Na by factors of 1000 to 10000. The data strongly suggested that, above 415C, most of the Cu impurity was interstitial.

N.H.Chan, W.J.Van Scriver: Physical Review B, 1975, 12[8], 3438-48

Table 271

Diffusivity of Cu in NaI Single Crystals