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Abstract The establishment of intimate electrode/electrolyte interface is very important in solid oxide fuel cells (SOFCs), because it plays a critical role in the overall cell performance and durability. In this study, Mn segregation and interface formation between directly assembled La 0.8 Sr 0.2 MnO 3 (LSM) electrode and yttrium-stabilized zirconia (YSZ) or gadolinium-doped ceria (GDC) electrolytes are studied using combined focused ion beam and scanning transmission electron microscopy (FIB-STEM). In the case of LSM/YSZ and LSM/GDC electrodes, a significant reduction in the electrode ohmic resistance is observed after cathodic polarization at 900 °C and 500 mA cm−2, indicating the formation of an intimate interface. However, LSM particles start to disintegrate at the electrode/electrolyte interface with the increase of polarization time in the case of LSM/YSZ electrode. On the other hand, the LSM/GDC interface is very stable with negligible microstructure change at the interface. Mn segregation from the LSM perovskite structure is identified under the influence of polarization in both LSM/YSZ and LSM/GDC electrodes. The results demonstrate that nature of the electrolyte plays a critical role in the electrochemical activity, microstructure, morphology and stability of LSM/electrolyte interface under SOFC operation conditions. Highlights • LSM/YSZ and LSM/GDC electrodes were prepared by direct assembly method. • Cathodic polarization induces the interface formation and Mn segregation. • The change in the microstructure of LSM/YSZ interface is substantial. • Nature of electrolyte plays an important role in the microstructure and stability of the interface. [ABSTRACT FROM AUTHOR]

The electrode behaviour of strontium (Sr)-doped LaMnO3 (LSM) electrodes is investigated by an electrochemical impedance spectroscopy technique over the temperature range 850–1000 °C and the oxygen partial pressure range 0.01–0.21 atm. The electrodes are screen-printed on 50 mm×50 mm 3 mol% Y2O3–ZrO2 electrolyte cells with an electrode surface area of 10 cm2. The impedance responses show two separable arcs and are analysed in terms of two different equivalent circuits with comparable information on the electrode processes at high and low frequencies. The electrode process associated with the high-frequency arc is essentially independent of O2 partial pressure with an activation energy of ∼74 kJ mol−1, while that at the low-frequency arc has an activation energy of ∼202 kJ mol−1 and a reaction order with respect to O2 partial pressure of ∼0.5 at low temperatures and ∼0.85 at high temperatures. The electrode processes associated with the low- and high-frequency arcs are discussed. [Copyright &y& Elsevier]