A surface counting technique was used to investigate 137Cs tracer diffusivity in pure single crystals. The data for temperatures ranging from 250 to 500C could be described by:

D (cm2/s) = 225 exp[-1.74(eV)/kT]

I.M.Hoodless, B.D.McNicol: Philosophical Magazine, 1968, 17, 1223-31