Symmetric electrodes for solid oxide fuel cells based on Zr-doped SrFeO3-δ

Abstract

SrFe1-xZrxO3-d (0<x<0.35) compounds have been investigated as potential symmetric electrode materials for solid oxide fuel cells (SOFCs). The crystal structure changes from orthorhombic to cubic perovskite when iron is partially replaced by Zr4+. The compounds with Zr-content x>0.1 are structurally stable under reducing atmospheres up to 800 ºC. The oxygen nonstoichiometry and thermal expansion coefficients of the compounds are determined by thermogravimetric analysis and high temperature X-ray diffraction respectively, and both decrease with increasing Zr-content, indicating that Zr4+ improves the redox stability of SrFeO3-d. Total conductivity and area specific resistance (ASR) are determined in air and 5% H2-Ar. SrFe0.75Zr0.25O3-d exhibits ASR values as low as 0.1 and 0.17 U cm2 in air and 5% H2-Ar at 750 ºC respectively. The performance of these compounds as both cathode and anode materials is tested in a single cell with 400 mm-thick La0.8Sr0.2Ga0.8Mg0.2O3-d (LSGM) electrolyte, reaching a maximum power density of 425 mW cm-2 at 800 ºC.