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Abstract

Point defects are of paramount importance for electroceramics. They are
key structure elements as regards materials functionality; but, in
addition, they are also decisive for chemical kinetics, hence for
preparation, conditioning, annealing and degradation phenomena.
Concentrations and mobilities of these charge carriers are
significantly changed at or near interfaces (or more generally higher
dimensional defects) giving rise to depletion, accumulation, and
inversion layers with respect to ionic and electronic carriers and
hence to distinct electrical and chemical effects. It is discussed how
these effects can be explained and how such knowledge can be used to
design electroceramics purposefully. Examples refer to ionically or
mixed conducting oxides and halides. Finally, in nano-structured
materials the spacing of interfaces becomes relevant in that local
properties can be severely affected. Such size effects do not only lead
to confinement effects in the case of electronic carriers but also to
anomalies with respect to ion conduction and mass transport. The
potential of the nano-regime for electrical and chemical properties of
electroceramics is discussed in the framework of a "soft materials
science". (C) 2003 Elsevier Ltd. All rights reserved.