Atomic-scale studies of silver segregation at MgOCu heterophase interfaces

Atom-probe field-ion microscopy (APFIM) is used to measure quantitatively the absolute values of the Gibbsian interfacial excess of Ag, ΓAg, at semi-coherent {222} MgOCu(Ag) heterophase interfaces. Atomically clean metal oxide/metal heterophase interfaces were obtained by internal oxidation of a pure ternary Cu(Mg,Ag) single-phase alloy to produce octahedral-shaped MgO precipitates, 10 to 30 nm in diameter, in a single-phase Cu(Ag) matrix. Precipitates are faceted on {222} planes. Random-area APFIM analysis was performed in the 〈111〉 direction of the Cu(Ag) matrix, perpendicular to one pair of {222} facets of every MgO precipitate. For a single precipitate dissected on an atomic scale, segregation levels at both “front” and “rear” interfaces are determined. The average measured value of ΓAg, at 500°C, is (2 ± 0.6) × 1015 atoms cm−2. This corresponds to about one monolayer coverage.