High-Temperature Structural and Electrical Properties of BaLnCo2O6 Positrodes

The application of double perovskite cobaltites BaLnCo(2)O(6-delta) (Ln = lanthanide element) in electrochemical devices for energy conversion requires control of their properties at operating conditions. This work presents a study of a series of BaLnCo(2)O(6-delta) (Ln = La, Pr, Nd) with a focus on the evolution of structural and electrical properties with temperature. Symmetry, oxygen non-stoichiometry, and cobalt valence state have been examined by means of Synchrotron Radiation Powder X-ray Diffraction (SR-PXD), thermogravimetry (TG), and X-ray Absorption Spectroscopy (XAS). The results indicate that all three compositions maintain mainly orthorhombic structure from RT to 1000 degrees C. Chemical expansion from Co reduction and formation of oxygen vacancies is observed and characterized above 350 degrees C. Following XAS experiments, the high spin of Co was ascertained in the whole range of temperatures for BLC, BPC, and BNC.