Characteristics of ABO3 and A2BO4 (A=Sm, Sr; B=Co, Fe, Ni) samarium oxide system as cathode materials for intermediate temperature-operating solid oxide fuel cell

Samarium strontium cobalt oxide with ABO(3) lattice structure, which is mixed ionic and electronic conductor (MIEC), is considered as a promising cathode material for intermediate temperature-operating solid oxide fuel cell (IT-SOFC) due to its high electrocatalytic property. Cathode material containing cobalt (Co) is unstable at high temperature and has a relatively high thermal expansion coefficient. In this study, samarium oxide cathodes with ABO(3) and A(2)BO(4) (A=Sm, Sr; B=Co, Fe, Ni) structure on Sm(0.2)Ce(0.8)O(1.9) electrolyte were investigated in terms of electrochemical property and thermal expansion property. Area specific resistance (ASR) was measured by ac impedance spectroscopy, and thermal expansion coefficient (TEC) was measured using a dilatometer. Microstructure of cathode was observed using a scanning electron microscopy. Sm(0.5)Sr(0.5)CoO(3-delta) with ABO(3) structure showed the ASR of 0.87 Omega cm(2) at 600 degrees C, and Sm(0.5)Sr(0.5)NiO(3 +/-delta), which actually has A(2)BO(4) structure, showed the lowest TEC value of 13.3 x 10(-6)/K. (C) 2007 Elsevier B.V. All rights reserved.