Cobalt-free composite cathode for SOFCs: Brownmillerite-type calcium ferrite and gadolinium-doped ceria

Anomalous room temperature magnetoresistance in brownmillerite Ca2Fe2O5

“…2 They possess a general formula A 2 B 2 O 5 /A 2 BB 0 O 5 (A ¼ Ca, Sr; B, B 0 ¼ Fe, Co), where half of the B cations adopt an octahedral oxygen coordination and the other half adopt a tetrahedral oxygen coordination. Ca 2 Fe 2 O 5 is one such compound consisting of alternating FeO 6 octahedral layers and FeO 4 tetrahedral layers, in which oxygen vacancies are ordered along (010) plane forming 1D diffusion pathway for oxygen ion migration in the tetrahedral layers 3 and contributing to the ionic conductivity of the compound. The crystal structure of Ca 2 Fe 2 O 5 is orthorhombic belonging to the Pcmn space group with associated lattice parameters a ¼ 5.599 A, b ¼ 14.771 A and c ¼ 5.429 A.…”

Ca- and Ni-Doped Pr0.5Ba0.5FeO3−δ as a Highly Active and Robust Cathode for High-Temperature Solid Oxide Fuel Cell

“…While other samples show only a single perovskite phase, PBCFNi30 has a brownmillerite phase as well as a perovskite phase . Generally, the brownmillerite oxides are well known to have a slightly high ionic conductivity and suppressed thermal expansion, so they may enhance the thermal stability without electrochemical degradation. , …”

“…27 Generally, the brownmillerite oxides are well known to have a slightly high ionic conductivity and suppressed thermal expansion, so they may enhance the thermal stability without electrochemical degradation. 27,28 For the primary study, the cathodes and the electrolytes should be chemically stable because the chemical reactions between them can generally increase the resistance and deteriorate the electrochemical properties by forming insulating secondary phases at the interface. 29−31 Figure 3 exhibits the chemical compatibility study of PBCFNi with YSZ and GDC electrolyte.…”

Design and processing parameters of La2NiO4+δ-based cathode for anode-supported planar solid oxide fuel cells (SOFCs)

“…Therefore, the thermal expansion match with the state-of-the-art electrolyte materials is regarded as one of the major advantages of the LNO cathode. On the other hand, cobalt-containing perovskite cathodes demonstrate a significantly higher thermal expansion coefficient (20.5 Â 10 À6 K À1 for La 0.6 Sr 0.4 CoO 3Àd [88]) than other cell component materials due to a low-to high-spin transition of Co 3þ [89]. Therefore, the large thermal expansion mismatch between the LNOeGDC cathode functional layer and the LSC current collecting layer causes high interfacial stresses, leading to structural damage during thermal cycling as shown in Fig.…”