Initial results on the Ag|CdO {222} interface: Atomic scale interfacial chemistry and sequencing of ordered cadmium/oxygen planes

Abstract

The bonding between metal-ceramic interfaces is dependent upon the crystallographic structure and chemical composition of this heterophase interface [1-4]. In the case of metal/metal oxide interfaces, the chemistry of the interface can control the properties of the bulk material. The terminating plane of a metal oxide at a heterophase interface may be a mixed cation-oxygen, pure oxygen, or pure cation plane. For example, ab initio calculations indicate that oxygen atoms in a terminating {002} plane of MgO bond to either Ag or Ti atoms in a metallic overlayer, while the composition of the terminating MgO {002} plane remains unchanged [1,3]. High resolution electron microscopy (HREM) is used to determine the crystallographic structures of metal/metal oxide interfaces [57]. Our recent studies of the copper/magnesium oxide (222} heterophase interface -produced by internal oxidation of Cu(Mg) alloys -using conventional transmission electron microscopy (CTEM), HREM, and atom-probe field-ion microscopy (APFIM) have demonstrated the atomic scale sharpness and chemical nature of the {222} terminating planes [8-10], In particular, it is found that magnesium oxide precipitates have a cube-on-cube orientation relationship with the copper matrix, are octahedrally-shaped, and are bound by {222} planes. APFIM results demonstrate directly that the interfaces are atomically sharp, and the sequence of {222}-type planes across the interface is CulOIMg... and not CulMglO ....