Properties of NI/YSZ cermets depending on their microstructure

A cermet (ceramic metal composite) of Nickel and Yttria stabilized Zirconia (YSZ) is the most commonly used fuel electrode for Solid Oxide Fuel Cells (SOFC). The properties of such cermets depend strongly on their microstructure. Several Ni/YSZ cermet samples with different Ni content and Ni and 8YSZ grain size have been prepared. The thermal expansion coefficient (TEC) of these samples was measured in air respectively hydrogen and shows a strong dependence on grain size ratio. The kinetic of the oxidation/reduction of theses samples was investigated. The oxidation of the cermet is faster than the oxidation of pure NiO and the reduction consists of 2 steps whereas the last step is splitted into 2 concurrent processes.