Abstract
Reaction diffusion and the Kirkendall effect in Ti-Si binary system have been studied by using sandwich-type bulk diffusion couples consisting of 99.99% Ti, 99.9999% Ti plates and a oriented Si wafer. The results have been compared with our previous one obtained by using 99.99% Ti/Si and 99.5% Ti/Si couples. The faster growth of TiSi 2 formed in these Ti/Si diffusion couples, the higher the purity of titanium. To identify the element which slows down the growth rate of TiSi 2 , the effects of oxygen, nitrogen, carbon and iron were studied by adding oxygen and nitrogen into 99.9999% Ti or by depositing carbon and iron on the Ti surface. It has been clarified that iron atoms slow down the growth of TiSi 2 . Silicon atoms diffuse 50 to 100 times faster than titanium atoms in TiSi 2 . Iron affects the diffusivity of Si more effectively than that of Ti. On the basis of these results the role of iron in the Ti/Si bulk reaction diffusion couple has been discussed by taking into account a possibility of diffusion barrier effect or grain boundary diffusion.
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