Tunable Oxygen Intake/Release Characteristics of Brownmillerite-Type Ca2AlMnO5+δ Involving Atomic Defect Formations

The oxygen intake/release characteristics were systematically studied for Ca 2 AlMnO 5+δ samples synthesized under precisely controlled oxygen pressures. Both the oxygen storage capacity (OSC) and operating temperature were systematically lowered as the oxygen pressure in the firing atmosphere increased. Notably, the sample fired under a 1% O 2 atmosphere exhibited sufficiently large OSC and superior oxygen intake/release kinetics to the pristine sample synthesized in an anaerobic condition. The high-angle annular dark-field scanning TEM observation revealed that the samples contain defects in their atomic arrangement when fired in oxygen-rich atmospheres. This result indicates that the oxygen intake/release characteristics of Ca 2 AlMnO 5+δ are sensitive to the synthesis condition and widely tunable even without chemical substitutions.