Characterization of Nd[sub 1−x]Sr[sub x]CoO[sub 3−δ] (0≤x≤0.5) Cathode Materials for Intermediate Temperature SOFCs

Abstract

The crystal chemistry, thermal expansion behavior, electrical conductivity, chemical compatibility, and electrochemical performance in intermediate temperature solid oxide fuel cells (SOFCs) of Nd1−xSrxCoO3−δNd1−xSrxCoO3−δ (0⩽x⩽0.5)(0⩽x⩽0.5) perovskite oxides have been investigated. The samples crystallize in an orthorhombic structure, and the lattice volume increases with increasing Sr content, x.x. The thermal expansion coefficient decreases with x,x, reaches a minimum at x=0.3,x=0.3, and then increases. The electrical conductivity increases with x,x, and the system exhibits a semiconductor-to-metal transition at around x=0.3.x=0.3. The electrocatalytic activity and power density increase with increasing x,x, reaches a maximum around x=0.4,x=0.4, and then decreases due to an interfacial reaction of the x=0.5x=0.5 sample with the electrolyte. The x=0.4x=0.4 sample shows a maximum power density value of 0.24W/cm20.24W/cm2 at 800°C in single cells fabricated with the La0.8Sr0.2Ga0.8Mg0.2O2.8La0.8Sr0.2Ga0.8Mg0.2O2.8 electrolyte and Ni­Ce0.9Gd0.1O1.95Ni­Ce0.9Gd0.1O1.95 cermet anode. © 2004 The Electrochemical Society. All rights reserved.