A combustion synthesis method to obtain alternative cermet materials for SOFC anodes

Homogeneous mixtures of nanocrystalline powders of Ni-YSZ, (Ni,Co)-YSZ, (Ni,Fe)-YSZ, and (Ni,Cu)-YSZ were obtained by combustion synthesis from mixtures of molten nitrates and urea. Electrolyte/anode bilayers were then prepared by pressing a cermet layer onto a previously pressed yttria-stabilised zirconia (YSZ) electrolyte layer, at room temperatures. and then co-firing; this yields a porous cermet anode, and a dense YSZ layer with good adhesion. The anode layer remains sufficiently porous even after firing at temperatures up to 1450 degreesC. This technique is thus suitable to obtain porous cermets for SOFC anodes with homogeneous distribution of the metallic and ceramic components. The effects of different parameters of this chemical preparation route, such as the furnace temperature, the amount of urea and the cooling rate, have been studied, together with the preparation of different compositions of cermets. These results have shown that the composition and the volume percentage of the metallic phases can be predicted. Easy control of the composition and a good reproducibility have been obtained. In terms of physical properties, nanometric particles with high specific surface area have been produced. The resulting electrodes co-pressed on the electrolyte have exhibited fine grains and porous microstructures, as well as a very good adherence to the electrolyte, even at high sintering temperature. (C) 2001 Elsevier Science B.V. All rights reserved.