Solid-state reactions between bulk samples of copper oxide and alumina have been studied using scanning electron microscopy and electron microprobe analysis. Both CuAl 2 O 4 and CuA10 2 were found to form during reactions in air at 1100 °C between CuO powder and single-crystal alumina substrates. The relative position of the CuAl 2 O 4 and CuA10 2 layers was observed to depend on the crystallographic orientation of the surface of the alumina substrate: CuAl 2 O 4 formed in contact with (0001) alumina substrates while CuA10 2 formed when the alumina substrate surface was (1120). Faceted Cu-amminate/alumina phase boundaries were observed to develop when single-crystal alumina rods were reacted with CuO, although the interfaces invariably tended to be wavy.

The faceting of alumina interfaces in the presence of a glass affects both grain growth and grain-boundary mobility during liquid-phase sintering. The geometry and movement of facets that form during this sintering process are expected to play an essential role in the development of the final microstructure, in particular, by their influence on the topology of the grain boundaries which ultimately control the properties of Alz03 compacts. A new method for studying the interaction between A1203 and a glass has been developed. A thin sample of A1203 suitable for examination in a transmission electron microscope is prepared and examined and then reacted with SiOz and CaO via the vapor phase. This experimental approach allows the faceting behavior of g l a s~/ A 1~0~ interfaces to be studied systematically without introducing unnecessary complications during subsequent sample preparation. Faceting occurs almost exclusively on the (0001) and (1102) planes. The interaction between glass and certain structured grain boundaries in alumina has been studied using polycrystalline thin films. [

The morphology, composition, and crystallographic orientation of the substrate influence the nucleation and growth of deposited thin films. A method for the preparation of controlled, characteristic surfaces is reported. The surfaces are suitable for the heteroepitactic growth of thin films. When used in the formation of electron-transparent thin foils, the substrates can be used to investigate the very early stages of film growth using transmission electron microscopy. The substrate preparation involves the cleaning and subsequent annealing to generate a surface consisting of a series of steps. The step terraces are formed on the energetically stable surface, and controlled nucleation and growth of films at step edges is found. The substrate materials prepared using this technique include (001) MgO, (001) SrTiO3, and (001) LaAlO3.