Emitter-tip radii measurements were used to study the diffusion of Ta at 1600 to 2400K. The results could be described by:

D (cm2/s) = 2.2 x 101 exp[-63.8(kcal/mol)/RT]

S.Hok, M.Drechsler: Surface Science, 1981, 107[2-3], L362-6