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 mixtur es of molten nitrates and urea. Electrolyte/anode bilayers were then prepar ed by pressing a cermet layer onto a previously pressed yttria-stabilised z irconia (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 temperat ures up to 1450 degreesC. This technique is thus suitable to obtain porous cermets for SOFC anodes with homogeneous distribution of the metallic and c eramic components. The effects of different parameters of this chemical pre paration route, such as the furnace temperature, the amount of urea and the cooling rate, have been studied, together with the preparation of differen t compositions of cermets. These results have shown that the composition an d the volume percentage of the metallic phases can be predicted. Easy contr ol of the composition and a good reproducibility have been obtained. In ter ms of physical properties, nanometric particles with high specific surface area have been produced. The resulting electrodes co-pressed on the electro lyte have exhibited fine grains and porous microstructures, as well as a ve ry good adherence to the electrolyte, even at high sintering temperature. ( C) 2001 Elsevier Science B.V. All rights reserved.