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Item type:Publication, Access status: with files , Correlating surface cation composition and thin film microstructure with the electrochemical performance of lanthanum strontium cobaltite (LSC) electrodes(Royal Society of Chemistry (RSC), 2014-02-26); ; ; ; La0.6Sr0.4CoO3-δ thin films of varying thicknesses (20-170 nm) were prepared by pulsed laser deposition on yttria-stabilized zirconia (100) substrates, and their electrochemical electrode performance was correlated with the chemical surface composition and microstructure (e.g. porosity, surface area). The surface cation composition was analyzed by an atomic etching procedure with on-line inductively coupled plasma optical emission spectrometry detection. The surface sensitivity of the method was increased by dynamically switching the etching reagent during the on-line analysis and quantitative results for even the top atomic layer were obtained. A water-soluble Sr-rich surface species could be quantified on top of the LSC films and in combination with electrochemical analysis of the films by impedance spectroscopy an improved understanding of the surface exchange resistance could be obtained. Microstructural features such as the effective porosity of the films became accessible by a combination of these methods.Publicationtype: Journal ArticleScopus© Citations 52 75 121 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrochemical properties of La₀.₆Sr₀.₄CoO 3 - δ thin films investigated by complementary impedance spectroscopy and isotope exchange depth profiling(Elsevier, 2014-01-22); ; ; ; The oxygen exchange and diffusion properties of La0.6Sr 0.4CoO3 - δ thin films on yttria stabilized zirconia were analyzed by impedance spectroscopy and 18O tracer experiments. The investigations were performed on the same thin film samples and at the same temperature (400 C) in order to get complementary information by the two methods. Electrochemical impedance spectroscopy can reveal resistive and capacitive contributions of such systems, but an exact interpretation of the spectra of complex oxide electrodes is often difficult from impedance data alone. It is shown that additional isotope exchange depth profiling can significantly help interpreting impedance spectra by giving reliable information on the individual contribution and exact location of resistances (surface, electrode bulk, interface). The measurements also allowed quantitative comparison of electrode polarization resistances obtained by different methods.Publicationtype: Journal ArticleScopus© Citations 29 79 151 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Cation diffusion in La₀.₆Sr₀.₄CoO 3 - δ below 800 °C and its relevance for Sr segregation(Royal Society of Chemistry (RSC), 2013-12-03); ; ; ; Cation diffusion was investigated in la₀.₆Sr₀.₄CoO 3 - δ (LSC) thin films on (100) yttria stabilized zirconia in the temperature range 625-800 °C. Isotopic ( 86Sr) and elemental tracers (Fe, Sm) were used to establish diffusion profiles of the cations in bi- and multi-layered thin films. The profiles were analyzed by time of flight-secondary ion mass spectrometry (ToF-SIMS). Grain and grain boundary diffusion coefficients of the cations were determined for LSC thin films with columnar grains-diffusion along grain boundaries is shown to be about three orders of magnitude faster than in grains. This could be verified for thin films with different grain size. A- and B-site cations showed very similar temperature dependencies with activation energies of ∼3.5 eV for bulk and ∼4.1 eV for grain boundary diffusion. The importance of cation diffusivities for surface segregation of Sr and thus for a major degradation mechanism of LSC cathodes in solid oxide fuel cells is discussed.Publicationtype: Journal ArticleScopus© Citations 107 100 211