Structure and Properties of Novel Cobalt-Free Oxides NdxSr1-xFe0.8Cu0.2O3-δ (0.3 ≤ x ≤ 0.7) as Cathodes of Intermediate Temperature Solid Oxide Fuel Cells

Novel cobalt-free perovskite oxides NdxSr1-xFe0.8Cu0.2O3-delta (NSFCx, 0.3 <= x <= 0.7) have been prepared and evaluated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC). Their structure, thermal expansion, electric, and electrochemical properties are investigated. The oxides exhibit all cubic structure and show excellent thermal and electrochemical performance stability. The Nd content (x) significantly affects the properties of NSCFx. NSFC0.5 has been found to be the optimum composition with a peak electrical conductivity of 124 S cm(-1) at 700 degrees C, an average thermal expansion coefficient of 14.7 x 10(-6) K-1 over 25-800 degrees C, a cathodic polarization resistance (R-p) of 0.071 Omega cm(2) at 700 degrees C, and a peak power density of 900 mW cm(-2) at 800 degrees C for samarium-doped ceria (SDC)-based single cells with NSFCx cathodes and Ni-SDC anodes. Moreover, no degradation has been observed for the R-p, at 700 degrees C within 350 h. The concentration of surface oxygen vacancies and composition dependent crystallographic parameters have been found to be the dominating factors on performance of NdxSr1-xFe0.8Cu0.2O3-delta as IT-SOFC cathodes.