The growth of spinel into AI2O3

The growth of cobalt aluminate spinel into an a-alumina substrate has been studied using transmission electron microscopy by combining imaging and selected area electron diffraction. It was found that for a (0001) alumina substrate the (111) plane of the spinel is usually slightly inclined to the basal plane of the a-alumina. The phase transformation does not therefore take place simply by the motion of Shockley partial dislocations as had previously been proposed. Models for the structure of the phase boundary are discussed and a new model proposed based on the new experimental results.