(Y0.5In0.5)Ba(Co,Zn)4O7 cathodes with superior high-temperature phase stability for solid oxide fuel cells

Abstract

(Y0.5In0.5)BaCo4−xZnxO7 (1.0 ≤ x ≤ 2.0) oxides crystallizing in a trigonal P31c structure have been explored as alternative cathode materials for solid oxide fuel cells (SOFC). At a given Zn content, the (Y0.5In0.5)BaCo4−xZnxO7 compositions exhibit superior phase stability compared to YBaCo4−xZnxO7 and InBaCo4−xZnxO7 at the operating temperatures of SOFC (600–800 °C). In the (Y0.5In0.5)Ba(Co4−xZnx)O7 system, the x = 1 sample offers a combination of good electrochemical performance, low thermal expansion coefficient (TEC), and enhanced chemical stability against Ce0.8Gd0.2O1.9 (GDC) electrolyte while demonstrating good phase stability at 600–800 °C for 100 h. Optimum cathode performance could be obtained by employing (Y0.5In0.5)BaCo3ZnO7 + GDC (50:50 wt.%) composite cathodes attached at 850 °C for 3 h as evidenced by ac-impedance spectroscopy, and the fuel cell performance of this composite cathode was evaluated using anode-supported single cells. With a combination of excellent high-temperature phase stability, low TEC, and good electrochemical performances, the trigonal (Y0.5In0.5)BaCo3ZnO7 composition is an attractive cathode candidate for intermediate temperature SOFC.