The stability of a calcium-aluminum-silicate liquid film, between 2 near-basal plane surfaces of sapphire, was studied at 1650C. Samples were prepared which had an average basal misorientation, across the interface, of 6 to 7 about <10•0>. The interfaces varied in orientation from 0 to about 38 with respect to the [00•1] direction. Three types of interface were observed. These were: faceted, solid/liquid interfaces, low-angle grain boundaries which consisted of aligned arrays of dislocations, and boundaries which consisted of alternating regions of dislocations and faceted solid/liquid interfaces. The type of interface which was observed depended upon the orientation of the interface, and could be predicted by using a construction that was based upon Wulff shapes. Because the type of interface depended upon the crystal alignment and the interface angle, the results suggested an absolute method for determining the surface free energy of wetted boundaries.

D.Y.Kim, S.M.Wiederhorn, B.J.Hockey, C.A.Handwerker, J.E.Blendell: Journal of the American Ceramic Society, 1994, 77[2], 444-53