Scandia-zirconia electrolytes and electrodes for SOFCS

The aim of this study was to assess the potential of scandia stabilised zirconias for use in high temperature fuel cells. Such materials offer much better performance than the conventional yttria stabilised materials and now it seems that availability and cost may not be hugely problematic. This offers a very important way forward to fuel cell manufacturing. It has been shown that a small addition of 2 mol% yttria to scandia stabilised zirconia results in formation of cubic phase and so avoids major phase changes which we believe to be detrimental to long term electrolyte stability. This addition of yttria can be achieved without significant impairment of the electrical conductivity of the scandia-stabilised zirconia. We have shown that the mechanical properties of these scandia-stabilised zirconias are inferior to the yttria-stabilised zirconias, but the difference is not that great. Thus we have identified a new range of composition for use in solid oxide fuel cell electrolytes, which exhibits good compromise between phase stability and electrical properties. Some experiments were also performed to investigate the properties of titania doped scandia stabilised zirconia as a possible fuel cell electrode material. This has shown that the scandia containing titania zirconias were better than those of the yttria analogue. However, electronic conductivity was still not high enough to use such materials as electrodes without appropriate current collection.