The impurity tracer diffusion of 59Fe, 51Cr and 57Co in chemical vapour deposited β-phase material was studied at 973 to 1873K. The temperature dependence of the bulk diffusion of Fe and Cr could be expressed by linear Arrhenius equations:

Fe:     D (m2/s) = 8.7 x 10-15 exp[-111(kJ/mol)/RT]

Cr:     D (m2/s) = 9.5 x 10-15 exp[-81(kJ/mol)/RT]

The diffusion coefficients of Fe and Cr were much higher than those for self-diffusion in SiC. The activation energies for the diffusion of Fe and Cr were equal to about 10% of those for C and Si in SiC. It was therefore assumed that an interstitial mechanism predominated for the diffusion of Fe and Cr in SiC. Dislocation diffusion coefficients were estimated from the deeper regions of the penetration profiles of Fe, Cr and Co.

Volume and Dislocation Diffusion of Iron, Chromium and Cobalt in CVD -SiC. K.Takano, H.Nitta, H.Seto, C.G.Lee, K.Yamada, Y.Yamazaki, H.Sato, S.Takeda, E.Toya, Y.Iijima: Science and Technology of Advanced Materials, 2001, 2[2], 381-8