No abstract

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 Σ5(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 below T≈1000 K but at T>1200 K it is no longer negligible.

Invited for this month'sc over picture is the group of Prof. Roger A. De Souza at RWTH AachenU niversity (Germany). The cover picture illustrates oxide ions moving from one crystal grain across agrain boundary to an adjacent grain in apolycrystalline oxide-ion conductor.T he mobilei ons perceive the boundary as an additional resistance arising from the disruption of the crystal structure at the boundary.T he resistance can be tuned by applying high electric fields.R ead the full text of the Communication at 10.1002/celc.202000773.

The Front Cover illustrates oxide ions moving from one crystal grain across a grain boundary to an adjacent grain in a polycrystalline oxide‐ion conductor. The mobile ions perceive the boundary as an additional resistance, arising from the disruption of the crystal structure at the boundary. The resistance can be tuned by applying high electric fields. More information can be found in the Communication A. R. Genreith‐Schriever et al.