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Free keywords:
grain boundary diffusion; space charge layer; finite element method; kinetic regimes
Abstract:
Diffusion in two grain boundary networks (parallel boundaries and
square grains) was considered in order to analyze the effects of space
charge layers on diffusion profiles. The space charge zones are
supposed to be depleted of mobile charge carriers, leading to a
blocking of transport of diffusing species. The finite element method
was used to numerically calculate the concentration distribution and
the corresponding integrated diffusion profiles. The accuracy of
determining the grain boundary diffusivity from the simulated profiles,
applying conventional equations was estimated. Blocking space charge
layers lead to a possible overestimation of the grain boundary
diffusivity in the type-B kinetic regime. Moreover, they lead to a
significant shifting of kinetic regimes and extremely large diffusion
times should be used to reduce errors, when determining the grain
boundary diffusivity in the type-A regime. (c) 2006 Elsevier B.V. All
rights reserved.
