An SEM conductive mode method is described for estimating the angle a grain boundary makes with the specimen surface, by varying the beam energy. Application of this technique to sloping grain boundaries in zinc oxide eliminates grain boundary geometry as a cause for a certain type of conductive mode contrast that is incompatible with existing models for varistor behaviour. Factors responsible for this contrast are discussed. Estimation of the grain boundary declination is also of use in crystallographic stu- dies of interfaces in polycrystalline zinc oxide, enabling the grain boundary plane to be estimated and hence providing the necessary information for calculating the grain boundary structure without recourse to (destructive) sectioning techniques.
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