Preparation of Ni–YSZ composite materials for solid oxide fuel cell anodes by the gel-precipitation method

Nickel oxide–yttria stabilized zirconia powder mixtures (Ni–YSZ) were prepared by the gel-precipitation method from aqueous or methanol solutions of the corresponding chlorides. The sinterability of the powder mixtures and hence their appropriateness as anodic material in solid oxide fuel cell technology (SOFC) is affected both by the history of the powder preparation and its composition. Relative densities of greater than 97% of theoretical of the mixed NiO–YSZ powder were achieved at sintering temperatures as low as 1300°C. In sintered samples, both NiO and YSZ, composites could be prepared as continuous phases if the chemical composition of the prepared powder mixture were carefully controlled. The continuity of the YSZ and Ni phases was preserved after reduction as well. If the ceramic YSZ phase was prepared as a continuous rigid framework there was practically no shrinkage of the sintered body during reduction, but the reduced matrices became porous and the relative densities were lowered. The microstructural and electrical properties of Ni–YSZ cermets, where the Ni content in the YSZ matrix is close to 35 vol.%, showed that the materials are appropriate for SOFC anode preparation.