| Abstract Scope |
Typical models of polycrystalline ionic materials treat the grain boundary properties as single valued, without consideration of the full range of responses that define the macroscopically measured average. Here we report a unique experimental platform suitable for local multimodal characterization of individual grain boundaries in bicrystal fibers. We observe 3 orders of magnitude variation in the grain boundary conductivity of ceria, as measured across six individual bicrystals. Linear sweep voltammetry, time-of-flight secondary ion beam spectroscopy, and electron backscatter diffraction analysis reveal correlations between grain boundary resistance, the concentration of impurities segregated at the grain boundaries, and the misorientation across the grain boundaries. These correlations, along with nonlinear response in the voltammetry measurements, point towards a grain boundary resistance that arises from impurity-generated space charge effects, with differing surface energies driving impurity segregation to differing extents. Countering these effects will likely require introduction of compensating defects rather than enhancing material purity. |