The temperature dependence of the bulk diffusivity of 192Ir in W single crystals was investigated, at 2000 to 2960K, by using the radiometric diffusion-zone sectioning method and materials of at least 4N-purity. It was found that the data:

D (cm2/s) = 3.2 x 10-1 exp[-120.9(kcal/mol)/RT]

could be explained in terms of the Lazarus-LeClaire vacancy model.

N.K.Arkhipova, S.M.Klotsman, I.P.Polikarpova, G.N.Tatarinova, A.N.Timofeev, L.M.Veretennikov: Physical Review B, 1984, 30[4], 1788-96

The best linear fits to the solute diffusion data ([5] to [25]) yield:

H (sd): Ln[Do] = 1.49E – 21 (R2 = 0.87); W(sd): Ln[Do] = 0.33E – 16.1 (R2 = 0.63)