Stability and oxygen-storage characteristics of Al-substituted YBaCo4O7+δ

A series of Al-substituted YBa(Co1-xAlx)(4)O7+delta samples was synthesized and characterized with respect to the capability to store large amounts of oxygen at low temperatures (at 200-400 degrees C) and the phase decomposition upon heating under oxidizing conditions at higher temperatures (above 550 degrees C). It was revealed that increasing the Al-substitution level up to x approximate to 0.10 boosts up the phase-decomposition temperature from similar to 550 to similar to 700 degrees C, while the unique oxygen absorption/desorption characteristics remain nearly the same as those of the pristine YBaCo4O7+delta phase. The maximum amount of excess oxygen absorbed by the Al-substituted YBa(Co1-xAlx)(4)O7+delta samples was determined to be as large as delta approximate to 1.45 for x = 0 10 (in 100 atm O-2 at 320 degrees C) Isothermal annealing experiments carried out for the same x=0.10 phase at 300 degrees C revealed that it could be reversibly charged and discharged with 1.2 oxygen atoms per formula unit by switching the gas flow from N-2 to O-2 and vice versa (C) 2010 Elsevier Inc All rights reserved.