V. Ravikumar et al., SPACE-CHARGE DISTRIBUTION ACROSS INTERNAL INTERFACES IN ELECTROCERAMICS USING ELECTRON HOLOGRAPHY .1. PRISTINE GRAIN-BOUNDARIES, Journal of the American Ceramic Society, 80(5), 1997, pp. 1117-1130
The role and importance of interface charge and the associated space-c
harge in governing the electrical activity of interfaces are well appr
eciated, and have been the focus of a large number of investigations.
Despite a considerable progress in this area, the direct determination
of the sign, magnitude of the interface charge, and the space-charge
potential associated with the interface double-Schottky barrier has re
mained elusive. We propose electron holography as a bulk sensitive too
l with subnanometer resolution to obtain direct real-space evidence of
space-charge, as well as determine the electrical activity of individ
ual grain boundaires (GBs) in electroceramics. Part I of this investig
ation is focused on the theory and practice of electron holography of
interfaces, in the context of pristine (undoped) GBs in SrTiO3. We sho
w that pristine GBs exhibit very little electron phase change, and tha
t the phase change is associated with a reduction in the mean inner po
tential and with any residual charge, both present by the virtue of th
e GB. This investigation forms the basis for the electron holography i
nvestigation of doped (charged) GBs in Part II. It is shown that quant
itative information about the magnitude, sign, and spatial extent of e
lectrical potential and charge, as well as defect densities across ind
ividual GBs in electroceramics, can be obtained using transmission ele
ctron holography.