CONTROL OF MICROSTRUCTURE OF NiO-SDC COMPOSITE PARTICLES FOR DEVELOPMENT OF HIGH PERFORMANCE SOFC ANODES

Three different types of nickel oxide (NiO)-samarium doped ceria (SDC) composite particles were synthesized using the spray pyrolysis technique. The starting conditions were controlled to produce (1) capsule-type particles in which NiO is enveloped with SDC, (2) matrix-type in which SDC is finely dispersed within a matrix of NiO and (3) hollow-type, with a shell of less than 100nm in thickness. The capsule- and matrix-type composite particles were spherical, whereas the hollow-type particles were observed to be a mixture of hollow spheres and flake-like pieces which were probably broken particles. Measurements of the performance of single cells with La0.9Sr0.1Ga0.8Mg0.2O3-delta as the electrolyte, La0.6Sr0.4CoO3-delta as the cathode and each of the three particle types as the anode were made at 750 degrees C. The cells fabricated from the matrix-type particles showed higher power density than those made from the capsule- and hollow-type particles. The better performance of the matrix-type composite was attributed to a lower ohmic loss. It is therefore considered that the matrix type of particle is likely to be best suited to the development of a fine and well-connected network structure which avoids aggregation of nickel phase during cell fabrication, resulting in a lower ohmic loss.