Improved mechanical properties and thermal expansion behavior of NiO-Y2O3 stabilized ZrO2 composite by addition of LaNbO4 for anode-support of planar solid oxide fuel cells

LaNbO4-NiO-Y2O3 stabilized ZrO2 (YSZ) composites are prepared and investigated as an anode-support material for solid oxide fuel cells. To tailor the coefficient of thermal expansion (CTE), electrical conductivity, fracture strength σ and fracture toughness KIC of the composite, various amounts of LaNbO4 from 0 to 30 wt.% are added into 53 wt.% NiO-47 wt.% YSZ composite. With LaNbO4 addition into the NiO-YSZ, σ changes insignificantly, whereas CTE decreases and KIC increases monotonously. For 30 wt.% LaNbO4-NiO-YSZ, the CTE is 12.4 × 10−6 K−1 (250-1000 °C), which is much closer to that of YSZ, and the KIC is 3.1 MPa-m1/2, which is 42% increase compared with that of the NiO-YSZ. The increase in fracture toughness is possibly due to the domain switch within LaNbO4 and the overall grain refinement of the composite. The electrical conductivity of the reduced composites decreases with increasing the amount of LaNbO4 and shows metallic conducting behavior with temperature.