NiYSZCermets

NiYSZCermets, or Ni-YSZ cermets, are nickel–yttria-stabilized zirconia ceramic–metal composites used primarily as anodes in solid oxide fuel cells and related solid oxide devices. The material combines a nickel metal phase with a yttria-stabilized zirconia ceramic matrix. Nickel provides electronic conductivity and catalytic activity for fuel oxidation, while YSZ offers oxygen-ion conductivity and structural support, enabling electrochemical reactions at the electrode.

The typical microstructure is a porous network of nickel particles embedded in a YSZ matrix, producing a large electrochemically active triple-phase boundary among nickel, YSZ, and the gas phase. Ni-YSZ cermets are usually prepared by mixing NiO and YSZ powders, shaping into a green body, and then calcining and reducing NiO to Ni. Common fabrication routes include powder metallurgy, tape casting, screen printing, and impregnation techniques, followed by sintering to achieve the desired porosity and connectivity.

Key properties include high electronic conductivity at operating temperatures (roughly 700–1000°C), good catalytic activity for hydrogen oxidation, and thermal expansion compatibility between Ni and YSZ. The porous network supports gas diffusion and maintains mechanical integrity during redox cycles.

Limitations and challenges involve Ni sintering and coarsening, which can reduce porosity and TPB length over time, susceptibility to carbon deposition when operating on hydrocarbon fuels, and redox instability under exposure to air. Redox cycling can degrade performance unless mitigated by microstructure design or protective strategies. Ongoing research explores alternative metal phases, doped ceramics, and microstructures to enhance stability and tolerance to fuels.