Ln1–xSrxCoO3−δ perovskite oxides are important mixed ionic electronic conductors with applications in electrochemical energy conversion. This manuscript reports a systematic investigation of the oxygen cycling capacity of a wide range of half-doped x = 0.5 compositions from Ln = La–Y using thermogravimetric analysis. A similar upper limit δmax = 0.35–0.40 is found, with the variation in storage capacity resulting from the highest accessible oxygen content (δmin). The best oxygen storage capacity of ∼0.3 mol O corresponding to ∼2 wt % is found for Ln = Pr–Sm. For Ln = Gd–Y, A-site ordered superstructures are found, linked to a deviation from the ideal 1:1 Ln:Sr stoichiometry, with compositions becoming more Sr-rich. These samples have notably reduced oxygen storage capacities. In situ neutron powder diffraction was used to probe the structural evolution of Pr0.5Sr0.5CoO3−δ under flowing nitrogen gas. This revealed extensive domains of phase coexistence between Imma, R3̅c, and cubic perovskite structures. Significant oxygen loss occurs above 450 °C at which point the cubic phase is the largest component of the sample. This study contributes new insight into structural stability and oxygen cycling performance of these important electrode materials.
Hesse et al. (Sun,) studied this question.