Tracer and sectioning methods were used to study the diffusion of 210Pb in single crystals of 5N-purity material. The results could be described by:

D (cm2/s) = 6.0 x 10-2 exp[-16.46(kcal/mol)/RT]

for diffusion parallel to the c-axis, and by:

D (cm2/s) = 7.1 x 10-2 exp[-15.71(kcal/mol)/RT]

for diffusion perpendicular to the c-axis.

D.C.Yeh, L.A.Acuna, H.B.Huntington: Physical Review B, 1981, 23[4], 1771-7