Effective Ca-doping in Y1-xCaxBaCo2O5+δ cathode materials for intermediate temperature solid oxide fuel cells

Ca-doping at the Y-site of Y1-xCaxBaCo2O5+delta (YCBC) double perovskites is shown as an effective strategy to develop a highly efficient, stable, lanthanide-free cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The proposed Ca-doping has a beneficial influence on the structural stability, thermal expansion coefficient, electronic and ionic transport, and electrochemical properties of YCBC oxides. The phase stability and durability at evaluated temperature are greatly enhanced by Ca-doping. The thermal expansion coefficients of Y1-xCaxBaCo2O5+delta are calculated to be 18.1-18.7 x 10(-6) K-1. At 800 degrees C, the conductivity is as high as 220 S cm(-1) for the Y0.8Ca0.2BaCo2O5+delta sample. Area specific resistances as low as 0.010, 0.018, 0.032, 0.068 and 0.142 Omega cm(2) at 850, 800, 750, 700 and 650 degrees C, respectively, are delivered by the Y0.8Ca0.2BaCo2O5+delta cathode in a La0.8Sr0.2Ga0.8Mg0.2O3-delta electrolyte supported symmetric cell. The maximum power densities of a full cell with the Y0.8Ca0.2BaCo2O5+delta/Ce0.9Gd0.1O2-delta composite cathode are registered to be 1066, 841, 634 and 430 mW cm(-2) at 850, 800, 750 and 700 degrees C, respectively. All the results clearly demonstrate that Ca-doped Y1-xCaxBaCo2O5+delta double perovskites are highly stable and effectively working candidate cathodes for IT-SOFCs.