Redox characteristics variations in the cation-ordered perovskite oxides BaLnMn(2)O(5+delta) (Ln = Y, Gd, Nd, and La) and Ca2Al1-xGaxMnO5+delta (0 = x = 1)

摘要

Two series of manganese-based oxygen storage materials, BaLnMn(2)O(5+delta) (Ln = Y, Gd, Nd, and La) and Ca2Al1-xGaxMnO5+delta (0 <= x <= 1), were synthesized and characterized to clarify cationic substitution effects on the oxygen intake/release behaviors of these materials. The thermogravimetric data revealed that the isovalent substitutions neighboring the active sites for oxygen intake/release are very effective. For BaLnMn(2)O(5+)delta, fully-reduced delta approximate to 0 products with larger Ln ions showed oxygen intake starting at lower temperatures in flowing O-2 gas, resulting in a systematic relationship between the onset temperature and the ionic radius of Ln(3+). Furthermore, the delta vs. P(O-2) plots at 700 degrees C indicated a systematic trend: the larger the ionic size of Ln(3+) is, the larger oxygen contents the Ln-products exhibit. For Ca2Al1-x-GaxMnO5+delta , on the other hand, the temperature-induced oxygen intake/release characteristics appeared to be influenced by Ga-for-Al substitution, where the onset temperatures of oxygen release (upon heating) and oxygen intake (upon cooling) are decreased with the increasing Ga content (x).