Oxygen Storage Capability of Brownmillerite-type Ca₂AlMnO_5+δ and Its Application to Oxygen Enrichment

The oxygen storage capability was investigated for Ca₂(Al_<i>x</i>Mn_1–<i>x</i>)₂O_5+δ (0.50 ≤ <i>x</i> ≤ 0.67) with a Brownmillerite-type structure. This oxide can store/release a large amount of excess oxygen (∼3.0 wt %) topotactically in response to variations in temperature and the surrounding atmosphere in a highly reversible manner. The capacity and response of oxygen storage are remarkable only in the vicinity of <i>x</i> = 0.50, that is, Ca₂AlMnO_5+δ, and rapidly deteriorated as the Al content increases. Owing to the high sensitivity in terms of oxygen nonstoichiometry, Ca₂AlMnO_5+δ exhibits oxygen intake/release ability when temperature swing between 500 and 700 °C is applied. With this characteristic feature of this oxide, a facile method for oxygen enrichment is demonstrated