Diffusion couples, in which one single-phase layer of silicide grew from saturated adjacent phases, were used to study the diffusion properties of Co-Si intermetallics at 914 to 1217C. The position of the Kirkendall marker plane within the reaction zones revealed that, over this temperature range, Co was very much the faster diffusing element in the Co2Si intermetallic. The intrinsic diffusivities of the components were essentially equal in the disilicide, and Si was almost the only mobile species in the monosilicide. The concept of the integrated diffusion coefficient was used to describe the growth kinetics of the intermetallic compounds. The integrated diffusion coefficient in an intermetallic was related to the tracer diffusivities of the components, and the thermodynamic stabilities of the phases which were involved in the interaction. The tracer diffusion coefficients of the elements in the CoSi2 and CoSi phases were obtained at various temperatures, and the results were found to be consistent with the usual Arrhenius relationship.

Formation of Co-Si Intermetallics in Bulk Diffusion Couples - Growth Kinetics and Mobilities of Species in the Silicide Phases. M.J.H.Van Dal, D.G.G.M.Huibers, A.A.Kodentsov, F.J.J.Van Loo: Intermetallics, 2001, 9[5], 409-21