Nature and Functionality of La_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ/ Gd_0.2Ce_0.8O_2-δ/ Y_0.16Zr_0.84O_2-δInterfaces in SOFCs

Interdiffusion phenomena and secondary phase formation at the interface La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) / Gd 0.2 Ce 0.8 O 2-δ (GDC) / Y 0.16 Zr 0.84 O 2-δ (YSZ) are correlated to linear and non-linear losses in symmetrical and full SOFC cells. FIB/SEM (focussed ion beam / scanning electron microscopy) tomography is applied for determining the local distribution of the primary phases LSCF, GDC, and YSZ and elemental analysis via STEM/EDXS (scanning transmission electron microscopy / energy dispersive X-ray spectroscopy) provides information on the secondary phase SrZrO 3 (SZO) and the interdiffusion between GDC and YSZ (ID). This reveals the effect of GDC co-sintering temperature (varied from 1100°C to 1400°C), alongside the sintering of LSCF at 1080°C, on these multi-layered microstructures. Electrochemical impedance spectra on symmetrical cells show that the polarization resistance ( ASR cat ) of the cathode/electrolyte interface is pronouncedly affected by three orders of magnitude, changing the overall power density of anode supported SOFC single cells at 0.8V by as much as a factor of 20. In conclusion, the chemical composition of the ID has a tremendous impact on the electrochemical efficiency of the investigated LSCF/GDC/YSZ interface, and processing parameters of anode supported cells with LSCF cathode have to be carefully chosen for individual SOFC cell concepts.