The ratio of diffusion coefficients in growing and non-growing compound layers

Abstract

The experimental data available in the literature show considerable, if not huge, differences between the values of diffusion coefficients of the elements A and B in a compound layer growing at the A-B interface and the values of diffusion coefficients of those elements in a piece of the same binary compound material but taken along. For example, the diffusion coefficients of iron and aluminium in the Fe2A15 phase material at 520 °C were reported by Larikov et al. [1] and Larikov [2] to have values of 1.9 x 10 -16 mZs -1 and 8.7 x 10 -15 m2s -1, respectively. On the other hand, when investigating the growth kinetics of the Fe2A15 layer at the interface between iron and aluminium, Heumann and Dittrich [3] found that the growth process was due mainly to the diffusion of aluminium atoms across the layer bulk. They established the following temperature dependence of the diffusion coefficient of aluminium in the growing Fe2A15 layer: DA1 = 3.3 X 10 -6 exp (--13 IO0/RT) m 2 s -1 (R in cal mole -1 K -1)