Evaluation of La_0.6Sr_0.4CoO_3--Ce_0.85Sm0.075Nd_0.075O_2- composite cathodes for intermediate temperature solid oxide fuel cells

Aiming to lower the operating temperature of solid oxide fuel cells down to 500-700 degrees C, a Co-containing composite cathode La0.6Sr0.4CoO3-delta-Ce0.85Sm0.075Nd0.075O2-delta (LSC-SNDC) is prepared by the solid-liquid method. The crystallinity, grain size and microstructure of LSC powders are analyzed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The LSC-SNDC cathodes with different mass ratios (LSC: SNDC = 100:0, 90:10, 70:30, 60:40 and 50:50) are implemented into symmetrical cells and full cells using screen printing. The effect of cathode sintering temperatures (900, 950, 1000, 1050 degrees C) is investigated at the symmetrical cell level. The lowest cathode polarization resistance (R-p) is obtained with the 50:50 sample sintered at 950 degrees C, demonstrating a R-p (symmetrical cell) of 0.0248, 0.0319, 0.0597, 0.1107 and 0.2304 Omega cm(2) and a maximum power density (full cell) of 1963, 1535, 1013, 585, and 302 mW cm(-2) at 800, 750, 700, 650 and 600 degrees C, respectively. The LSC-SNDC (50:50) cathode exhibits a low thermal expansion coefficient of 12.3 x 10(-6) K-1 and good compatibility with other cell components, as confirmed from SEM observations. The current work demonstrates that LSC-SNDC is a promising cathode material for intermediate temperature solid oxide fuel cells.