Electrical Conductivity, Thermal Expansion and Electrochemical Properties of Perovskites PrBaFe2–xNi x O5 + δ

Abstract

In order to evaluate applicability of mixed-conducting PrBaFe2–xNi x О5 + δ perovskites for cathodes of solid oxide fuel cells (SOFCs), their crystal structure, thermal and chemical expansion, electrical conductivity and electrochemical behavior were studied. The solubility limit of nickel in PrBaFe2O5 + δ corresponds to x = 0.8. At x > 0.2, the disordered cubic phase transformed into the tetragonal phase. The maximum level of conductivity (50–120 S/cm) at the operating temperatures of SOFC was found for the composition with the maximum nickel content, PrBaFe1.2Ni0.8О5 + δ. This material is also characterized by moderate thermal and chemical expansion relative to other ferrite-nickelates. The polarization resistance of a porous PrBaFe1.2Ni0.8О5 + δ cathode in a cell with a protective Ce0.6La0.4O2–δ layer and a solid electrolyte (La0.9Sr0.1)0.98Ga0.8Mg0.2O3–δ was ~0.9 Ohm cm2 at a temperature of 1073 K, atmospheric oxygen pressure, and current density of–120 mA cm–2.