Analysis of Gibbsian segregation at heterophase interfaces using analytical transmission electron microscopy: a novel approach

A new and general approach to analyze Gibbsian segregation at heterophase interfaces is proposed. It is tested on the possible segregation of indium dissolved in a copper matrix to interfaces between MnO precipitates and the copper matrix. In the present approach the actual concentration of the segregating element in a monolayer at the interface is obtained. This is in contrast to line-scans or maps where the concentrations determined are a convolution of the concentration profiles with the electron probe and where, for general interfaces, the deconvolution problem cannot be solved accurately. This is possible because the present approach uses explicitly the information offered by hetero-interfaces. The occurrence of indium segregation is clearly demonstrated and the indium concentration in the terminating copper monolayer at the parallel {111} Cu/MnO interface is determined to be 15±3 at%, whereas the average indium concentration in the copper matrix is 3.8±0.4 at%. A comparison between experimental high-resolution transmission electron microscopy images of the interface, atomistic calculations and image simulations indicates that indium atoms in the terminating monolayer of copper at the interface segregate to generalized oxygen nodes present between the dislocation lines of a trigonal misfit-dislocation network with <110> line direction and 1/6<112> Burgers vector. Theoretically, an indium concentration at the interface of 14±7 at% is estimated to be favorable, which compares well with the experimental findings.