In situ examination of oxygen non-stoichiometry in La0.80Sr0.20CoO3-δ thin films at intermediate and low temperatures by x-ray diffraction

Structural evolution of epitaxial La0.80Sr0.20CoO3-delta thin films under chemical and voltage stimuli was examined in situ using X-ray diffraction. The changes in lattice parameter (chemical expansivity) were used to quantify oxygen reduction reaction processes and vacancy concentration changes in lanthanum strontium cobaltite. At 550 degrees C, the observed lattice parameter reduction at an applied bias of -0.6V was equivalent to that from the reducing condition of a 2% carbon monoxide atmosphere with an oxygen non-stoichiometry delta of 0.24. At lower temperatures (200 degrees C), the application of bias reduced the sample much more effectively than a carbon monoxide atmosphere and induced an oxygen non-stoichiometry delta of 0.47. Despite these large changes in oxygen concentration, the epitaxial thin film was completely re-oxidized and no signs of crystallinity loss or film amorphization were observed. This work demonstrates that the effects of oxygen evolution and reduction can be examined with applied bias at low temperatures, extending the ability to probe these processes with in-situ analytical techniques. (C) 2014 AIP Publishing LLC.