Determination of grain boundary potentials in ceramics: Combining impedance spectroscopy and inline electron holography

Abstract

Abstract The electrostatic potential arising from charge bound at grain boundary cores in ceramics and the accumulation of space charge in their vicinity is in many cases made responsible for the ion blocking or conducting behavior of electroceramics. While interpretation of impedance spectra of nominally undoped and acceptor doped SrTiO3 ceramics and bicrystals implies that grain boundaries are positively charged and accompanied by fairly wide regions of negative space charge on both sides, a critical analysis of electron holography data available in the literature yields very narrow potential profiles of the opposite sign. This paper attempts to reconcile this apparent discrepancy by showing that within the Mott–Schottky model, impedance data which implies space charge dominated grain boundary resistivity must be interpreted in terms of even wider space charge regions than generally assumed. A review of electron holography results from grain boundaries in SrTiO3 is extended by new results which were obt...