Development of Low Thermal Expansion Ca2Fe2O5 Cathode Materials for Solid Oxide Fuel Cells

Abstract

A cobalt-free Ca2Fe2O5 oxide with alternating perovskite layers of corner-sharing FeO6 octahedra and layers of FeO4 tetrahedra have been synthesized and investigated as a potential cathode material for solid oxide fuel cells (SOFCs). Our preliminary electrochemical testes show a rather high area specific resistance (1.03 Ωcm2 at 700 oC) for ~20 μm thick layers with GDC electrolyte. The electrochemical performances are improved in the composite with 30 wt%GDC (CG30-70, 0.31 Ωcm2 at 700 oC). In addition, thermal expansion coefficient (TEC) values of CG30-70 specimen demonstrated 12.9x10-6 oC-1 in the range of 25-900 oC, which provides good thermal expansion compatibility with the GDC electrolyte. The long-term thermal stability and thermal cycle tests of the CG30-70 cathode were carried out. The stable ARS values were observed during both the long-term thermal stability test and the thermal cycle test. An electrolyte supported (300-μm-thick) single-cell configuration of CG30-70/CGO/Ni-CGO delivered a maximum power density of 563 mWcm-2 at 800 oC. The unique composite composition of CG30-70 demonstrates improved electrochemical performance and good thermal stability for IT-SOFCs.