Synthesis and performances of Ni–SDC cermets for IT-SOFC anode

NiO–SDC (samaria-doped ceria) composite powders were synthesized using a urea-combustion technique. The structure, electrical conducting, thermal expansion and mechanical properties of the Ni–samaria-doped ceria (Ni–SDC) cermets have been investigated with respect to the volume contents of Ni. No chemical reaction product between the two constituents was detected for the cermets sintered at 1200–1300 °C for 4 h in air and reduced at 800 °C for 2 h in a 60%N2 + 40%H2 atmosphere. A porous microstructure consisting of homogeneously distributed Ni and SDC phases together with well-connected grains was observed. It was found that the open porosity, electrical conductivity, thermal expansion and bending strength of the cermets are sensitive to the volume content of Ni. The Ni–SDC cermets containing 50–60 vol.% Ni were ascertained to be the optimum composition. These compositions offer sufficient open porosity of more than 30%, superior electrical conductivities of over 1000 S/cm at intermediate temperatures (600–800 °C), a moderate average thermal coefficient of 12.6–13.5 × 10−6 between 100 and 800 °C and excellent bending strength of around 100 MPa.