Grain-Boundary Structures Associated with Ionic Transport in Gd-Doped Ceria Nanostructured Electrolyte

High resistive ionic transport at the grain boundary is one of the most decisive factors for designing sophisticated nanostructured electrolytes as oxide ceramics. Here, the grain boundary structures are investigated for nanostructured electrolytes, ceria (CeO 2 ), Gd-doped ceria (GDC), and Li-doped GDC (Li-GDC), by means of element-specific positron annihilation spectroscopy. The angstrom-scale spaces with negative charge are identified in addition to the grain-to-grain contacts essentially identical to the bulk and void-like open spaces created by lattice mismatching. The grain-boundary structures associated with oxygen ionic transport are demonstrated on the basis of space charge theory for the grain-boundary conductivity.