Abstract

We have investigated the effect of M = Ti4+ and V5+ doping on the crystal structure and on the thermal, electrical, and electrochemical properties of SrCo1-xMxO3-delta (x = 0.03 and 0.05) perovskite oxides performing as cathodes in solid oxide fuel cells (SOFC). The characterization of these materials included x-ray (XRD) and neutron powder diffraction (NPD) measurements. The introduction of Ti4+ and V5+ replacing Co in SrCoO3-delta leads to the stabilization of a tetragonal perovskite superstructure at room temperature with a = a(0), c = 2a(0) (a(0) approximate to 3.9 angstrom) defined in the P4/mmm space group, containing two inequivalent Co positions. Flattened and elongated (Co,M)O-6 octahedra alternate along the c axis sharing corners in a three-dimensional array (3C-like structure). The thermal expansion coefficients of SrCo0.95Ti0.05O3-delta and SrCo0.97V0.03O3-delta have been measured between 25 and 850 degrees C. The electrical conductivity at the SOFCs working temperatures (650-850 degrees C) seems to be sufficient to yield a good performance in IT-SOFC; the polarization resistance in symmetrical cells is as low as 0.016 Omega cm(2) at 850 degrees C for M = Ti. In single test cells these materials generated a maximum power of 824 mW/cm(2) at 850 degrees C with pure H-2 as a fuel. This good performance make these systems promising candidates as cathode materials in SOFC. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.