Effect of La0.6Sr0.4Co0.2Fe0.8O3-δ microstructure on oxygen surface exchange kinetics

Abstract

a b s t r a c t Available online xxxx La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) is a mixed ionic-electronic conducting perovskite (ABO 3 ) material which has attracted significant research interest in recent years as a cathode for solid oxide fuel cell (SOFC) applications at intermediate temperatures (500°C-750°C). Fundamental understanding of the oxygen surface exchange kinetics and diffusion in LSCF cathodes is necessary to optimize the cell performance at the required operating temperatures. In this study, we controlled the surface microstructure and crystalline orientation of LSCF thin films on (100) Gd 2 O 3 -doped CeO 2 thin films (GDC) prepared by pulsed laser deposition on yttria-stabilized zirconia (YSZ) single crystal substrates. Tailoring of the LSCF microstructure was achieved by modifying the underlying GDC thin film surface morphology and microstructure. To clarify the effect of the LSCF microstructure on its oxygen surface exchange kinetics, we employed the 18 O/ 16 O oxygen isotope exchange technique in conjunction with secondary ion mass spectroscopy (SIMS) depth profile analysis. Comparison of the qualitative features of the measured concentration of the 18 O profile and evaluation of the oxygen surface exchange coefficient k* were performed and the results correlated to the LSCF microstructure.

Nanoionics and interfaces for energy and information technologies

“…Independent works from Fleig's and Tarancón's groups recently discovered fast oxide-ionic conductivity along grain boundaries in LSM, reporting up to 5-6 orders of magnitude of improvement in oxide-ion diffusivity compared to the bulk, which might be associated to straininduced defects and corresponding changes in the oxidation states of LSM constituent cations [6,31]. In this sense, dominating ionic conductivity at the grain boundary level was reported for PLD-growth thin films of La0.8Sr0.2Mn1-xCoxO3±δ [103], LaCo0.6Ni0.4O3 [104] and consistently from Develos-Bagarinao et al for YSZ, CGO, La0.6Sr0.4Co0.2Fe0.8O3-δ and La0.6Sr0.4CoO3-δ [105,106].…”

The effect of sub-surface strontium depletion on oxygen diffusion in La0.6Sr0.4Co0.2Fe0.8O3−δ

“…70 Dislocation networks and twins are also present in LSCF. 23,71 Strontium segregation and particle growth rate have been shown to be inuenced by both compressive and tensile strains, 72 suggesting that a strained superstructure can act as a fast pathway for strontium. Using high-temperature environmental scanning electron microscopy (HT-ESEM) and electron back-scattered diffraction (EBSD), the nucleation sites for Sr-O based particles appear to coincide with twin boundaries in the middle of grains at particular orientations.…”

Insights into the enhancement of oxygen mass transport properties of strontium-doped lanthanum manganite interface-dominated thin films

“…Silicon-supported substrates (employed by Tarancón and co-workers for IEDP-SIMS in reference [12]) will generate a higher strain than YSZ substrates due to a higher thermal mismatch between Silicon and YSZ/LSM. This can increase the defect concentration at the grain boundary level and the total strain in the thin film, which has been demonstrated to affect its transport properties [28,29].…”