Uncommon oxygen intake/release capability of layered cobalt oxides, REBaCo4O7+: Novel oxygen-storage materials

An uncommon oxygen intake/release phenomenon was discovered for the layered cobalt oxide system, REBaCo4O7+δ (RE = Dy, Y, Yb, and Lu). Compounds, REBaCo4O7+δ, can intake oxygen up to δ ≈ 1.3 and release it in atmospheric O2 as temperature increases in a narrow range below 400 °C. The oxygen intake/release processes are highly reversible, being controlled by both temperature and/or oxygen partial pressure. The oxygen-rich phase (with δ = 1.0–1.3) releases upon heating all excess oxygen atoms in a single-step process about 400 °C, whereas oxygen intake occurs in the temperature range of 200–350 °C when slowly cooled in an O2-containing atmosphere. The oxygen intake/release characteristics are also strongly dependent on the choice of RE. This suggests that the crystal structure of the compounds is the key for this uncommon phenomenon. Obviously these compounds are promising candidates for oxygen-storage applications.