Tensile lattice distortion does not affect oxygen transport in Yttria-stabilized zirconia-CeO₂ heterointerfaces

Biaxially textured epitaxial thin-film heterostructures of ceria and 8 mol % yttria-stabilized zirconia (8YSZ) were grown using pulsed laser deposition (PLD) with the aim to unravel the effect of the interfacial conductivity on the charge transport properties. Five different samples were fabricated, keeping the total thickness constant (300 nm), but with a different number of heterointerfaces (between 4 and 60). To remove any potential contribution of the deposition substrate to the total conductivity, the heterostructures were grown on (001)-oriented MgO single-crystalline wafers. Layers free of high-angle grain boundaries and with low density of misfit dislocations were obtained, as revealed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) analysis. The crystallographic quality of these samples allowed the investigation of their conduction properties, suppressing any transport effects along grain boundaries and/or interfacial dislocation pathways. Electrochemical impedance spectroscopy (EIS) and secondary ion mass spectroscopy (SIMS) measurements showed that for these samples the interfacial conductivity has a negligible effect on the transport properties.