LaNbO4-NiO-Y2O3 Stabilized ZrO2 Anode-Support Materials for Solid Oxide Fuel Cells

As anode-support materials for solid oxide fuel cells, porous LaNbO4-NiO-Y2O3 stabilized ZrO2 (YSZ) composites (LNY), containing 0, 5, 10, 15, and 20 wt% of LaNbO4 and designated as 0LNO, 5LNO, 10LNO, 15LNO, and 20LNO, respectively, are prepared by tape casting and sintering. They are investigated for their microstructure and mechanical, electrical and thermal expansion properties. The porosity of as-sintered LNY is around 30%, and that of reduced LNY cermets decreases from 47% for reduced 0LNO to 43% for reduced 20LNO. The fracture strength (sigma(f)) of LNY is higher than that of the reduced form; however, both of them are not rather sensitive to the amount of LaNbO4, depending on crack-originating flaws in the specimens. The fracture toughness (K-IC) of LNY increases with LaNbO4 content and is 1.87 MPa.m(1/2) for 20LNO, which is more than 20% increase from that of 0LNO; however the K-IC for reduced LNY is higher than that of LNY, and decreases with increasing LaNbO4 content due to the decreased amount of ductile metallic Ni phase. The conductivity of reduced LNY depends on Ni content and is higher than 289 S/cm at temperatures below 900 degrees C. The coefficient of thermal expansion (CTE) of both LNY and reduced LNY is in the range between 12.4 and 11.4 x 10(-6) K-1; which is closely matched with that of YSZ electrolyte.