Electronic and structural properties of La0.4Sr0.6Ti1-yCoyO3±d electrode materials for symmetric SOFC studied by hard X-ray Absorption Spectroscopy

Abstract

We present combined Synchrotron X-ray Absorption Near Edge Spectroscopy (XANES) and<br />Extended X-ray Absorption Fine Structure (EXAFS) study of La0.4Sr0.6Ti1yCoyO3d<br />(0 <=y <= 0.5), which are promising electrode materials for symmetric solid oxide fuel cells.<br />The measurements were performed at room temperature at the Ti and the Co K-edges in<br />order to determine the local structural and electronic changes around the two transition<br />metals. We find that Ti remains in a higher formal valence (around 4þ) independent of the<br />Co concentration. In contrast to this, dramatic and systematic changes are observed for the<br />Co as a function of y.We conclude that the stability of the Ti4þ triggers the A-site deficiency<br />in our samples and predicts that oxygen vacancies are much more easily formed at large<br />Co content, which in turn will greatly enhance the performance as electrode material.