Microstructure tailoring of combustion-derived Ni-GDC and Ni-SDC composites as anode materials for intermediate temperature solid oxide fuel cells

The Ni-GDC and Ni-SDC cermets with tailored microstructures are potential candidates for anode materials in intermediate temperature SOFCs. In this work, a modified citrate-nitrate combustion synthesis was employed for the preparation of cermets. It was demonstrated that the preparation technique ensured randomly distributed phases of NiO and GDC or SDC on a nanometre scale. Microstructure analysis revealed that during sintering under various conditions (from 1150 to 1400 °C), the NiO phase grew faster than the GDC or SDC phases; however, phases remained well within the sub-micrometre range. In order to describe the overall relative electrical conductivity of the cermets, the sine-wave approximation of conductivity change for porous materials was used. Higher relative densities of the cermets resulted in improved electrical conductivity. The most appropriate sintering temperature, which ensured relatively small grains and at the same time sufficiently high electrical conductivity, for both materials was determined to be 1200 °C.