Redox behaviour and ageing of GDC-Co cermets: A comparison between lamellar and conventional cermets

Lamellar cermets produced from directionally solidified eutectic ceramic precursors are now being considered an alternative option to conventional cermets in SOFC technology. The reduction behaviour of lamellar and conventional oxide-oxide ceramics of the same composite, but prepared through two different methods, as well as the ageing effects of the resulting cermet have been analysed with a view to its possible application as the SOFC anode. On the one hand, lamellar ceramics composed of gadolinium doped ceria (GDC) and cobalt oxide (CoO) with their eutectic composition have been produced by directional solidification from laser floating zone technique (LFZ). On the other hand, fine ceramics with the same composition have been prepared from a conventional wet chemistry route in order to assure the production of small and homogeneous grain size samples (conventional cermets). In both cases, reduction kinetic experiments in the 500-750 °C temperature range have been performed. The lamellar cermets show a competing reduction process that is not thermally activated and this has been linked to the existence of a high number of low energy interfaces in the lamellar material. Evolution of the electronic conductivity and porosity with ageing was used to evaluate the stability of the samples under operating conditions. In this sense, lamellar cermets show a better performance.