SYNTHESIS AND CHARACTERIZATION OF NON-STOICHIOMETRIC HEXAGONAL Dy1-xYxMnO3+δ

Materials exhibiting reversible oxygen storage/release capacities are currently explored for elevated-temperature air separation and production of high-purity oxygen for several industrial processes. The development of improved oxygen storage or carrier materials is also critical to growth of new energy related technologies such as oxy-fuel and chemical looping combustion and reforming for clean coal energy and synthesis gas production. Currently, Ce1-xZrxO2 are used around 500°C and have storage capacities of 400–500 μmol-O/g. Guided by our previous studies of the temperature and oxygen content dependence of the perovskite tolerance factor, we have developed synthesis method and discovered that hexagonal Dy1-xYxMnO3+δ materials exhibit superior storage/release capacities as high as 2000 μmol-O/g in air. Large changes of oxygen content occur on cycling between unusually low temperatures near 250°C and 350°C, and are observed when materials transform among stoichiometric and interstitial oxygen-excess structures. These changes are related to alternation of Mn coordination to oxygen and are readily visible in material's resistivity and chemical expansion.