Faceting of the interface between Al2O3 and anorthite glass

The {10 (1) over bar 0} and {11 (2) over bar 0} Al2O3 surfaces have been equilibrated in contact with anorthite liquid at 1600 degrees C. The structure of the resulting Al2O3/glass interfaces has been characterized using transmission electron microscopy. Both interfaces were unstable in the presence of the liquid and reconstructed lo give regular arrays of facets. The (10 (1) over bar 0) interface developed (10 (1) over bar 1) and ((1) over bar 012) facets while the (11 (2) over bar 0) interface developed {hh<(2h)over bar>3} facets. It is proposed that the (10 (1) over bar 0) glass/crystal interface is thermodynamically stable, but that the (11 (2) over bar 0) interface facets due to interface-step migration. The microstructure thus shows that both the crystallography and the anisotropic interface energies are important in determining the wetting/dewetting behavior of glass on Al2O3. (C) 1998 Acta Metallurgica Inc.