Oxygen desorption properties of perovskite-type SrFe1-xCoxO3-d: B-site mixing effect on the reduction properties of Fe and Co ions

To understand the B-site mixing effect in perovskite-type SrFe1-xCoxO3-delta, we evaluated the relationship between the oxygen desorption properties and the reduction behavior of Fe and Co ions using thermogravimetry and in situ X-ray absorption spectroscopy. The valence states of Fe and Co ions were estimated to be 3.56+ and 3.27+, respectively, which remained constant with changes in composition. Maximum oxygen desorption occurred at x 1/4 0.2 below 800 C. As temperature was increased and oxygen was released, a relationship was observed between the valence and coordination number changes of each B-site ion; these changes were more pronounced for the Fe ions than for the Co ions. In SrFe1-xCoxO3-delta samples, oxygen adjacent to Fe ions was released more readily than oxygen adjacent to Co ions. This conclusion is supported by the electronic states of the two B-site ions. These results are important for the design of new oxygen storage materials.