Characterization of out-of-plane transport properties of Sm0.2Ce0.8O2−δ in all-thin-film hetero-epitaxial structures

We have fabricated all-thin-film solid oxide fuel cell (SOFC) heterostructures and investigated the transport properties of Sm0.2Ce0.8O2−δ (SDC20) in an out-of-plane measurement geometry. The SOFC heterostructures, consisting of a bottom SrRuO3 or Ba0.93La0.07SnO3 electrode and an SDC20 electrolyte, were fabricated on SrTiO3 (001) substrates via pulsed laser deposition. The hetero-epitaxial nature and atomically sharp interfaces between the electrolyte and the electrode were confirmed by x-ray diffraction and high-resolution scanning transmission electron microscopy. Out-of-plane electrochemical impedance spectroscopy measurements indicate that the electrochemical properties of the SDC20 thin films are quantitatively consistent with those of bulk SDC20 in a wide temperature range from 350 to 550 °C. Our results demonstrate that all-thin-film heterostructures can serve as a platform for direct investigation of intrinsic transport properties of electrochemical materials.