Crystallization of calcium hexaluminate on basal alumina

Abstract

Abstract The epitactic growth of calcium hexaluminate (CA6) on the basal plane of alumina was observed during an investigation of the interaction between silicate glass films deposited on single-crystal alumina (α-Al2O3). Two distinctly different orientation relationships occurred. The first can be described as perfect hexagon-on-hexagon epitaxy with (1120)CA6∥(1010)Al2O3 and (0001)Al2O3 ∥(0001)CA6. This relationship has 1.1% lattice misfit in the substrate plane; the misfit is accommodated at the interface by a hexagonal network of misfit dislocations. In the second relationship the CA6 grains are rotated about the substrate normal and can be explained by the coincident-site lattice model for phase boundaries. Both orientation relationships emphasize the influence of substrate crystallography on the crystallization process.