METAL CERAMIC INTERFACE ADHESION - BAND-STRUCTURE CALCULATIONS ON PT-NIO COUPLES

Under certain annealing conditions Pt-NiO couples form NiPt intermetallic layers at the interface. It has been suggested that an observed 4-fold increase in the ultimate shear strength of the interface upon inclusion of a 1-nm-thick NiPt interlayer is caused by metal-oxygen bonding at the interface. Extended Huckel calculations, within the tight-binding formalism, have been performed on a series of Pt- and NiPt-NiO metal-ceramic couples to elucidate the nature of the bonding at these interfaces. The calculations showed an approximately 5-fold increase in adhesion energy in NiPt-NiO over Pt-NiO. This is attributed to the more efficient electron donating capability of nickel compared to that of platinum. Bonding across the interface is found to decrease with increased electron donation as interfacially antibonding orbitals are filled. Theoretical reasons for the eventual mechanical failure in the oxide component are adduced.