M. Kubicek, T. Huber, A. Wachter-Welzl, A. Penn, G. M. Rupp, J. Bernardi, M. Stöger-Pollach, H. Hutter, J. Fleig:
"Electrochemical properties of La0.6Sr0.4CoO3−δ thin films investigated by complementary impedance spectroscopy and isotope exchange depth profiling";
Solid State Ionics, 256 (2014), S. 38 - 44.

Kurzfassung englisch:
Cation diffusion was investigated in La0.6Sr0.4CoO3-δ (LSC) thin films on (100) yttria stabilized zirconia in the temperature range 625-800 °C. Isotopic ((86)Sr) 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.

Mixed conductor,Impedance spectroscopy,Isotope exchange,Surface exchange,Diffusion,ToF-SIMS

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