Atomic-scale structure and chemistry of ceramic/metal interfaces—I. Atomic structure of {222} MgO/Cu (Ag) interfaces

Abstract

Ceramic/metal (C/M) {222} MgO/Cu (Ag) heterophase interfaces, prepared by internal oxidation, are studied by scanning transmission electron microscopy (STEM). The observed spacing between misfit dislocations (1.45 nm) in a 〈110〉 projection is in agreement with the prediction of Bollmann's geometric O-lattice theory and experimental values in the literature for {222} MgO/Cu interfaces. It is concluded that the {222} MgO/Cu (Ag) interfaces are semicoherent and contain a trigonal network of pure edge misfit dislocations parallel to 〈110〉-type directions, with an ( a/6)〈211〉-type Burgers vector. Misfit dislocations are also found in a standoff position at a distance of a single (111) spacing of the Cu (Ag) matrix. Extra intensity at the interface, in some angular dark-field images indicates silver segregation, in agreement with our atom-probe field-ion microscope results. On the metal side of the interface, extra intensity is observed in five atomic layers, which corresponds to a total silver enrichment of approximately 0.7 effective monolayers.