HIGH-RESOLUTION ELECTRON-MICROSCOPY OF BN ON MGO - A MODEL CERAMIC CERAMIC INTERFACE

Studies of ceramic-ceramic interfaces by high-resolution electron microscopy have been facilitated by a novel approach to specimen preparation. Coatings of a variety of cerarmics can be applied by various techniques to the surfaces of nonporous cerarmic particles of simple geometric shape, and the resulting interfaces can be examined directly without the necessity for ion-beam milling. For example, coatings of boron nitride prepared from a polymeric precursor have been applied to the surfaces of crystalline oxides such as MgO, Al2O3 and TiO2. The initially amorphous BN wets the crystalline oxide surfaces and crystallizes to form tough, adherent coatings of hexagonal BN. On crystalline specimens, the hexagonal BN grows with the {002} layer planes locally parallel to the oxide surface in each instance, permitting interfaces between the {002} BN layers and particular oxide planes to be studied. The most successful results have been obtained to date from studies of BN on MgO{110} surfaces. The work described here details the characterization of the atomic structure of these model BN/MgO interfaces by methods of high-resolution electron microscopy.