Microstructural and high-temperature mechanical characteristics of nickel oxide/zirconia composites for solid oxide fuel cells

NiO/8YSZ (8 mol% Y2O3-stabilized ZrO2) composites with different NiO contents (10, 20 and 40 mol%) have been fabricated by a conventional route of mechanical mixing of NiO and 8YSZ powders and sintering at 1500 °C for 10 h in air. The resulting microstructures have been characterized by electron microscopy. In 10 and 20 mol% NiO/8YSZ, the composite is formed by isolated NiO particles surrounded by zirconia matrix grains; this phase is interconnected in the 40 mol% NiO/8YSZ composite. Mechanical tests at constant strain rate and at constant load were conducted on these materials at temperatures of up to 1350 °C. Different behaviors were found depending on the percolation of the NiO phase. Microstructural observations after deformation are essential to understand the overall mechanical behavior of the composites.

► Fabrication of NiO/8 mol% Y2O3-stabilized ZrO2 (8YSZ) composites.
► Two interpenetrated structures for 40 mol% NiO content.
► Mechanical behavior depends strongly on percolation of NiO phase.
► 40 mol% NiO composite becomes damage-tolerant with a large ductility.