(Y _0.5In _0.5)Ba(Co,Zn) ₄O ₇ cathodes with superior high-temperature phase stability for solid oxide fuel cells

(Y _0.5In _0.5)BaCo _4-xZn _xO ₇ (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 (Y _0.5In _0.5)BaCo _4-xZn _xO ₇ compositions exhibit superior phase stability compared to YBaCo _4-xZn _xO ₇ and InBaCo _4-xZn _xO ₇ at the operating temperatures of SOFC (600-800 °C). In the (Y _0.5In _0.5)Ba(Co _4-xZn _x)O ₇ system, the x = 1 sample offers a combination of good electrochemical performance, low thermal expansion coefficient (TEC), and enhanced chemical stability against Ce _0.8Gd _0.2O _1.9 (GDC) electrolyte while demonstrating good phase stability at 600-800 °C for 100 h. Optimum cathode performance could be obtained by employing (Y _0.5In _0.5)BaCo ₃ZnO ₇ + 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 (Y _0.5In _0.5)BaCo ₃ZnO ₇ composition is an attractive cathode candidate for intermediate temperature SOFC.