ATOMIC-STRUCTURE OF MISFIT DISLOCATIONS IN METAL-CERAMIC INTERFACES

In this paper we present a combined experimental and theoretical study of misfit dislocations in metal-ceramic interfaces. The goal is to re veal the atomic structure of the cores of misfit dislocations and rela te it to the bonding strength between the two materials. Two interface s in the niobium-sapphire system corresponding to different interface planes between the Nb and Al2O3 crystals, (01 ($) over bar 10)(Al2O3)p arallel to(11 $$($) over bar 2)(Nb) and (0001)(al2O3)parallel to(111)( Nb), have been investigated. Misfit dislocations were observed to be p resent in Nb with no stand-off away from the interface, and their core s were investigated using high resolution electron microscopy. Atomist ic studies of these misfit dislocations have been carried out using a very simplified model for both the ceramic crystal and the atomic inte ractions across the interface. A good agreement between the calculated and observed core structures has been attained for certain values of the cohesive strength across the interface and the results are discuss ed in terms of establishing relationship between the atomic structure of misfit dislocations and interfacial cohesion.