Chemical stability and oxygen permeability of La0.4Ba 0.6Fe1-xZnxO3-δ Perovskite: The effects of Zn substitution

Abstract

Perovskite oxide, La0.4 Ba0.6 FeO3-δ (LBF), is a typical cobalt-free, mixed ionic-electronic conductor. This work explored B-site doping in LBF by partially substituting iron with Zn, which results in La0.4 Ba0.6 Fe1-x Znx O3-δ (LBFZx). An investigation on the effects of Zn doping was then conducted. The introduction of Zn in LBFZx largely augments the concentration of oxygen lattice vacancies and the chemical resistance against reduction in the H2 (5%) / N2 atmosphere. This conclusion was drawn from the results of X-ray diffraction and temperature-programmed reduction. Furthermore, the O2 temperature-programmed desorption showed us that lattice oxygen desorption is affected by the vacancy concentration and the amount of movable lattice oxygen. The oxygen permeability of the LBFZx membrane increased from 800 to 950°C, with increasing Zn 2+ -doping extent (x-value) from 0 to 0.1, but the improvement discontinued with further increase in the x value from 0.1 to 0.2, namely both LBFZx (x=0.1 and 0.2) membranes presented the same oxygen permeation flux as high as 0.73 mL cm-2 min-1 at 950°C. Nevertheless, perovskite LBFZx with x=0.2 exhibited superior chemical stability in reducing atmosphere at 900°C over that with x=0.1. © 2010 The Electrochemical Society.