A common impurity in polycrystalline commercial alumina is Si since silica is often added as a sintering aid. There have been several studies on impurities in alumina, and substantial degree of grain boundary segregation has been found to occur. Alumina-metal composites have found several applications especially in the electronic industry and consequently systems such as alumina-copper have been studied exhaustively. However, the role of impurities in metal-alumina composites has not been fully explored. Studies of Pt-alumina composites has shown that silicon is present at the interface of vacuum, diffusion bonded samples. Our earlier studies have shown that Si indeed segregates to the triple junctions and grain boundaries in alumina and in alumina-copper composites, often Si segregates to the metal-ceramic interfaces as well. This investigation concentrates on the distribution of silicon in copper-alumina in comparison to aluminum-alumina composites.

The metal-ceramic composites were prepared by diffusion bonding 99.99% pure metal foils sandwiched in between commercially available sintered alumina (∼99.5% pure) substrates for several hours in vacuum.