The Intrinsic Structural Resistance of a Grain Boundary to Transverse Ionic Conduction

AR Genreith-Schriever and JP Parras and HJ Heelweg and RA De Souza, CHEMELECTROCHEM, 7, 4718-4723 (2020).

DOI: 10.1002/celc.202000773

Ion transport across grain boundaries in diverse polycrystalline ionic conductors is often found to be hindered. Such behaviour is commonly attributed to the presence of a highly resistive second phase or to the presence of space-charge zones, in which mobile charge carriers are strongly depleted. One other possible cause - the severe perturbation of the crystal structure within the grain-boundary core - is widely ignored. Employing molecular dynamics (MD) simulations of the model sigma 5(310)001 grain boundary in fluorite-structured CeO2, we demonstrate an approach to extract the intrinsic structural resistance of a grain boundary (to ionic transport across it), and we determine this excess resistance as a function of temperature. Compared with space-charge resistances predicted for a dilute solution of charge carriers the structural resistance of this interface is orders of magnitude smaller at temperatures belowT approximate to 1000 K but atT>1200 K it is no longer negligible.

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