ABSTRACT
SEM-EBIC studies have been carried out on two simplified varistor compositions to investigate barrier structures formed at individual grain boundaries. Both resistive and charge separation contrast effects were observed. The strength of the resistive contrast was found to vary with dopant, being stronger in the manganese-doped than in the antimony-doped material. EBIC contrast due to charge separation was observed at some interfaces in both samples. An asymmetry in EBIC contrast was found to be governed by the orientations of the grain boundary planes on either side of the interface.
