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SAM investigations of the segregation of sulphur in polycrystalline α‐iron
Author(s) -
Eisl M. M.,
Reichl B. M.,
Böhmig S. D.,
Störi H.
Publication year - 1992
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.7401901117
Subject(s) - sulfur , crystallite , diffusion , grain boundary , nitrogen , carbon fibers , impurity , chemistry , auger electron spectroscopy , molybdenum , analytical chemistry (journal) , metal , auger , monolayer , metallurgy , materials science , crystallography , thermodynamics , microstructure , atomic physics , biochemistry , physics , organic chemistry , chromatography , composite number , nuclear physics , composite material
Scanning Auger microscopy (SAM) and AES investigations of the segregation of non‐metal impurity atoms (sulphur, nitrogen, carbon and phosphorus) in polycrystalline high‐purity (>99.99%) α‐iron samples were performed in the temperature range 500–800°C. At the beginning of the heating, nitrogen segregates homogeneously and quickly but in the equilibrium state the whole surface is covered with nearly half a monolayer of sulphur. During the first measurements, the segregation of sulphur was ruled by a combined bulk and grain boundary diffusion mechanism with a t 1/2 law, resulting in a net‐shaped structure of the surface concentration of sulphur. After repeated heating and sputtering, the contribution of grain boundary diffusion becomes smaller and the segregation rate of sulphur decreases as a consequence of sulphur depletion of the bulk. The segregation kinetics of the individual grains differ strongly owing to the differences between the extent of sulphur depletion of the grains and can be described very well by a t 3/2 law in the initial stage of the segregation process. In a later phase, surface diffusion of sulphur from the grains, which have almost reached the equilibrium sulphur coverage, leads to an almost homogeneous sulphur coverage of the surface with only small and diffuse lateral variations.