Structural and chemical evolution of the SOFC anode La _0.30Sr_0.70Fe_0.70Cr_0.30O _3-δ upon reduction and oxidation: An in situ neutron diffraction study

Although some perovskite oxides have been shown to be stable solid oxide fuel cell (SOFC) anodes, the actual crystal structure of these materials under operating conditions is largely unknown. In this paper, the structural evolution of the SOFC anode La_0.30Sr_0.70Fe_0.70Cr _0.30O_3-δ was studied at 800 and 900 °C (similar to SOFC operating temperatures) in progressively reducing and oxidizing environments. The perovskite was shown to be stable down to a pO₂ of 10^-20 atm at 800 °C and a pO₂ of 10^-18 atm at 900 °C, at which point a spinel phase formed. Further reduction led to the formation of Fe metal. The phase separation of La_0.30Sr _0.70Fe_0.70Cr_0.30O_3-δ was also shown to be completely reversible with an increase in the partial oxygen pressure and reoxidation of the sample.